Vernalization
​Many hop growers are asking this question as the abnormally mild weather persists across much of the USA. For most growers in northern latitudes; probably not much effect will be noted.  Average hop vernalization temperature requirements of 6 weeks below 38 degrees Fahrenheit will still be met, resulting in normal burr and cone development later in the season. Expect an earlier emergence of pests and disease that the milder winter failed to kill.

For growers in more southern latitudes the story could be completely different. Effects on the hops in the southern tier could include: lack of proper vernalization, increased pest pressure, and increased prevalence and severity of hop diseases like downy and powdery mildews.

Hop vernalization requirements vary by hop genotype and varieties that require longer chilling periods may not properly reset back to the juvenile spring phase required to grow and produce a normal yield of cones.  One of the first signs of incomplete vernalization is uneven spring emergence of new shoots within plants of the same hop variety. Growers in the PNW have noted that this uneven emergence follows through the entire growing season; affecting cone-set, yield, alphas, and maturity dates.  The cone-bearing sidearms may not extend properly and only produce cones on the terminal ends. Many affected hop plants showed up to a 6 week delay of burr initiation and a 30 to 50% loss in total potential yield.

​Fertile soil is a mixture of well-balanced minerals, high organic matter, humus, humic, fulvic and carbonic acids, good aeration and bountiful microbial life. The biology or life in the soil is at its healthiest when the nutrients are plentiful and balanced, and there is sufficient oxygen and water. The top soil region is the most vital portion of the soil profile; holding about 70% of the life and 70% of the organic matter. In a typical soil, below 6 inches plant roots are feeding on mostly soluble nutrients since the micro-organisms are not able to thrive due to insufficient oxygen levels.  Many minerals are tightly bound to the subsoil colloidal particles are only made available to plants through complex soil interactions with organic acids leaching downward from the topsoil. It is critical to maintain the organic matter content in soils for them to remain balanced and healthy. 

​Reducing soil compaction is a major primary factor in maintaining nutrient availability.  Simply put; higher levels of oxygen at deeper soil depths increase the total quantity of micro-organisms like bacteria, fungi, actinomycetes, algae, nematodes and protozoa. These microbes contribute directly to the release of soil nutrients to the plant. Some species of specialized symbiotic mycorrhizae can tolerate low oxygen levels and can colonize roots much deeper than other species of beneficial microbes; providing deeper sources of nutrients and providing root protection against pathogens. There are many very complex symbiotic relationships going on between plant roots, organic matter, colloidal soil particles and micro-organisms that support overall plant growth.

It is important to note that soil that is worked too wet destroys air and water soil pore space, destroying the oxygen-rich environment that microbes need to thrive. Soil that is worked too dry creates similar problems. Tending soil for optimum production means adding minerals and organic matter every year when soil conditions are optimum. Well balanced fertile soil makes for higher crop yields, higher quality, with less disease and insect pressure.  Soil testing may indicate all nutrients and minerals may be present but these may not be available to the plants if the soil is poorly maintained.

​Growers should become familiar with how to interpret the soil and foliar test results. Knowing why, when, and how to complete a field test is equally important to getting accurate results. Here's the basics:

• Hops require different levels and balances of nutrients at different growth stages during the season.  For example: Phosphorus is critically important in early spring for new root development; at burr onset; and rebuilding energy going into winter.  Nitrogen is essential during the climbing and side arm development stage; but not during cone maturation or during preparation for winter dormancy. Extra zinc and boron are specifically required at burr initiation. Various major and micro-elements play different roles during each phase of hop development.  
• Spring soil testing- shows what the general levels are of all nutrients and soil pH going into the season. Do this test before the first major round of spring hopyard cultivation. This allows time to incorporate amendments like lime, sulfur, or phosphate. Be sure the test you choose includes all the micro-elements; not just the major N-P-K basics.
• Mid-season foliage testing : do a foliage test just prior to bine side arm initiation. When the small buds in the leaf axis on the climbing bine start to extend is the first sign side arms are about to push. Follow the instructions from the testing lab on which leaves to select.  The goal is to identify if the nutrients potassium, zinc, and boron are present in sufficient quantities to set burrs and cones for maximum yields.  If the tests show deficiencies, there is still time for quick corrective soil amendments or foliar-fed nutrients. This test is useful to see what nutrients the plant is actually taking up and available versus what may be indicated on the soil test. Compare the two tests to determine if any nutrient deficiencies or imbalances are causing blocking of other nutrients.
• Post-harvest soil testing – Shows what was removed by the plants and dissipation, what’s left, and what needs to be replaced going into winter dormancy.  Specifically check the levels of phosphorus, potassium, and organic matter. If soil pH has shifted or compaction are identified as issues, early fall is a good time to apply corrective amendments like phosphate, potassium, lime, and gypsum.

​The aerobic topsoil zone is usually only 6-7” deep and should be the primary zone tested for most crops. Hopyard soil samples should be taken from in the hop row; within 18 to 24 inches of the hop’s crown structure, where most nutrient depletion occurs. Perennial crops like hops may need to be sampled at greater depth to determine toxicity issues such as sodium, boron, carbonates, or residual herbicides.  If the soil has been mechanically deep-tilled with a subsoil implement or plowed, soil sampling could go to 20” plus. Using a tube type soil probe or a shovel, take a minimum of five probes in different zones of the area being tested. Scrape away any surface organic material or you will get an abnormally high reading. Do not combine probes from areas that are not uniform to the sample desired; for example when observing rocky, clayey, silty, flooded conditions; or when noting differences in crop or weed growth occurs. Sample these areas separately but do not combine them with the “normal” sample. Mix the representative 5 or 6 soil probe samples together to create a single sample.  Mix deep samples separately from shallow samples. Combined it should be about 1½ to 2 cups minimum of mixed soil.  Do not touch or mix the soil samples with your hand. Don’t use a rusty shovel. Place sample in a container approved by the soil testing lab of your choice.
The highest rates of soil fertility are seen when the testing done in May and June; the lowest in the winter. To get consistent comparative results, test soil at the same time of the year.  This allows comparisons of the annual soil tests to spot changes in the soil fertility from season to season.

​There are many labs around the country that give soil test results.  Every lab uses different testing methods so the comparative numbers may not be the same lab to lab. It is best to select one lab consistently to track annual testing results.  The categories below are all part of a complete soil test.
(Note: To covert pounds per acre to pounds per 100 square feet divide by 440.)

Increasing organic matter levels will help with the soil texture, structure, drainage, aeration, water holding capacity and availability, nutrient availability, root development and dramatically improve soil biology. Organic matter (humus) holds three times more nutrients than most clay soil types and up to 5 times as much available water.

2% or less organic matter is considered poor. Over 4% O.M. to 10% is ideal. Above 10% organic matter can often inhibit micro-nutrient uptake, and if composed primarily of woody materials will greatly reduce nitrogen availability. (Microbes breaking down wood cellulose use large amounts of nitrogen.) Most crop soils benefit from adding organic matter every year; especially if tilled or intensively farmed. Adding composts, manures, cover crops, and other organic mulches are the best choices for increasing organic matter.
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Side Note: Working overly wet soils destroys organic matter and adds to soil compaction. Adding fresh  non-composted organic matter such as raw wood chips high in cellulose will require additional nitrogen to compensate for the amount used by microbes breaking down the cellulose fibers.

Phosphorus is an important macro nutrient used in the storage and transfer of energy in the plant. It is essential in every metabolic growth process, protein synthesis, sugar development, and in nitrogen fixation. It is crucial for new root development. Optimum phosphorus levels are needed for rapid seedling and root growth, winter hardiness, disease resistance, efficient water use, early maturity, and maximum yield. Phosphorus needs to be placed and incorporated where it will be used; as it is less mobile in the soil than any other nutrient. It does not leach down in the soil profile like the macro nutrients nitrogen and potassium. Some cover crops can move phosphorus to deeper areas of the soil, where it will become available for other crops only after the cover crop roots decay.  This is why cover crops should be plowed down and incorporated; rather than being left as a perennial row cover.

Phosphorus becomes immobilized at low pH by large concentrations of aluminum, zinc and iron, and at high pH by too much calcium. Soils with high levels of Al, Zn, or Fe may need additional P applications to counter balance and provide adequate levels for optimal plant growth.

Soft rock phosphate is the fastest working phosphate.  300#/acre is the normal recommended minimum application.  Up to 2000#/acre of soft rock phosphate is often incorporated in severely deficient soil types.  Phosphites are not the same as phosphates! (Read More)  A complete soil test may contain two phosphorus tests:

• P1 tests immediate availability. 25 ppm is the minimum and above 40 ppm is ideal.
• P2 tests for future availability. 40 ppm is the minimum and 60 ppm is ideal. Above 60 PPM often ties up trace minerals such as zinc and copper. The greater the OM level, the greater the availability of phosphorus.​

Potassium is a macro nutrient that regulates the pace of plant metabolic activities. It is essential for photosynthesis and protein synthesis as well as carbohydrate transport and storage. It promotes root sugar reserves, winter hardiness, cell development, strong cellular walls and stems. Potassium improves water use efficiency, increases yield, improves crop quality, and reduces incidence of disease. Potassium is mobile within a plant and can translocate from older leaves to newer growth.  Soluble potassium is easily leached from soil profiles and needs to be replaced annually; like nitrogen.

Most soils have less than 1% of the existing potassium available due to insufficient microbial activity and organic matter content. There are about 30,000 to 50,000 lbs. per acre of potassium in an average soil, but most of this is not plant available until microbial activity releases it. It is possible to release small amounts of potassium over time by increasing microbial activity with compost, compost tea and cover crops. It is the second most probable nutrient to be deficient after nitrogen.

Applications of granular sulfate of potash (50% K2SO4) are timed in early fall (Read More) and spring to perennial crops. Additional soluble grade potassium fertilizer may be added to irrigation during the growing season, or foliar fed if severely deficient. Avoid winter and late fall applications after plants have gone dormant. Excess potassium will not create toxicities, but will block uptake of other nutrients; so single large applications are not as favorable as multiple applications throughout the season. Too much potassium ties up boron, calcium and manganese.
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2% Cation saturation potassium is the minimum and 5% to 7% is more optimal.

Magnesium is an essential micronutrient found in the chlorophyll of green plants. It is also necessary for metabolic processes and in every operation involving phosphorus. Magnesium levels have important interactions with calcium, sulfur, and nitrogen. The ratio of magnesium to calcium should be around one to six. Excess magnesium will reduce potassium availability.
Having a soil with too much magnesium will take more nitrogen because the excess magnesium makes the soil colloids bind too tightly. Excess magnesium is what makes most clay type soils “tight”, restricting air and water availability, water drainage, root development and restricting microbial activity and organic matter decay. Applications of garden gypsum are often recommended for clay-type soils with elevated levels of Mg to loosen the soils.

Higher levels of magnesium in a sandy soil will help to tighten loose sand. For sandy soil the optimum level would be 16% to 20% and for clay soils closer to 12%.  Mg availability is also closely tied to soil pH; so it is important to monitor the soil pH.
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Note: Two pounds of sulfur will leach out one pound of magnesium when there is at least 60% calcium saturation.

Calcium is the building block of cell division with strong cell walls and membranes; it also controls water movement in and out of plant cells and reacts with plant waste products and neutralizes toxic materials. Calcium is locked into a plants cellular structure, and thus is immobile once it is utilized by the plant. Calcium activates many of the soil microbial enzyme systems; it improves microbial activity and it enhances root uptake of other nutrients.  Calcium is critical for balancing excess nitrogen and for disease suppression. Having the correct amount of calcium in the soil will require less nitrogen for optimal plant growth. Calcium will help loosen compacted soil and make more nitrogen available. Too much calcium can tie up all other nutrients especially magnesium, potassium, boron, zinc and copper. Gypsum and lime are two common sources of calcium. Application of sulfur neutralizes excess calcium.

Calcium cation (+) saturation levels need to be over 60% before adding additional gypsum (calcium sulfate) to lower excess magnesium levels; otherwise the sulfur in the gypsum will neutralize the calcium first. Add sufficient limestone first to raise calcium levels to 60%, and then add enough gypsum to raise calcium levels to 68%. One third of applied calcium from lime / gypsum will become available the first year and it takes 3 years to be completely utilized. Solution grade limestone will quickly become 100% available within 1-3 months.
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Limestone applied to the surface of the soil will work its way into the soil at the rate of 1” per year if not incorporated. Calcium leaches down in soils with excess rain or irrigation. Consult with a soil specialist to determine the proper amounts to add as amendments to avoid raising soil pH levels to undesirable levels. 

 Widespread in most soil types, sodium is found in all plant material. Although it does not seem to be necessary for the growth and development of plants, it is taken up by the plant, particularly when potassium is low. Sodium seems to be able to partly substitute for potassium and can block potassium uptake if in excess levels.

Excess sodium is a problem in many dry areas particularly if the irrigation water is alkaline. Sodium toxicity to plants is often observed in saline and alkali lands and unfavorable soil structures can be present due to high sodium as well. Excess sodium suppresses soil biology, root development and nutrient availability. Any time the sodium and potassium levels together are over 10% then the manganese won’t be able to get into the plant.  Normal rainfall and irrigation leaches excess sodium out of soils.
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Note: Excess Chloride (Cl) levels are often associated with high sodium levels. Chlorides can reach toxic levels and should also be monitored if sodium levels are high. (Read More)

Nitrogen is macro nutrient and is an essential constituent of proteins found in chlorophyll, enzymes, and hormones. It has a predominant role among the macro soil nutrients and is needed by plants in substantial amounts. It is also the most likely nutrient to be deficient. Deficiency limits crop growth and yield. It is rapidly taken up by crops, but much of the applied nitrogen is lost by volatilizing into ammonia, or by leaching away by water. Nitrogen in the soil is the most stable when found in organic humus and microbial bodies. Increased active organic matter and microbes increases the level of plant-available nitrogen. However, an excess of nitrogen can produce an imbalance in plant metabolism and produce overly soft growth; resulting in poorer plant quality and higher susceptibility to plant pathogens, increased transpiration water loss by the crop, reduced flavor and keeping qualities.

Dangers of nitrogen overuse include: zinc deficiency, copper deficiency, burnt out organic humus and microbes, drives out calcium but leaves magnesium (tighter soil) and depletes sulfur. The more nitrogen that is applied in excessive amounts; the higher the replacement level of the other nutrients that were carried away by the leached nitrogen will have to be.

Nitrogen and sulfur can leach out calcium. Nitrogen never leaches out magnesium, only sulfur does. The best methods to stabilize proper nitrogen levels are to use and incorporate cover crops, composts and manures before, during, and after each crop growing cycle.
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In hopyards, the bulk if the nitrogen (50 to 80%) should be available when seasonal hop growth is between 6 to 14 feet tall.

Sulfur is a component of several amino acids that are essential for forming plant protein. It helps develop enzymes and vitamins, promotes nodule formation on legumes, aids in seed production, is necessary for good root development, improves taste, increases protein and reduces nitrates. It is involved in the chlorophyll production process, and sulfur deficient plant tissue symptoms resemble nitrogen deficient symptoms.

Sulfur is commonly deficient in all soils except where sulfur based fertilizers are applied. Without sufficient sulfur the rate of organic matter decomposition is decreased, due to a deficiency in sulfur reducing decomposing bacteria and Actinomycetes. Humus and organic matter helps hold sulfur in the soil. Sulfur feeds microbes and builds organic matter levels. Sulfur is very soluble and should be added in some form every spring to soils with low organic matter content. (Soils high in active organic matter often have adequate sulfur.)

Two pounds of sulfur can leach out one pound of either calcium or magnesium. Start applications of sulfur if calcium levels are above 60% base saturation. Sulfur can also be used to leach out excess sodium and boron. If gypsum (calcium sulfate) is applied, the sulfur will leach out the excess sodium cations, and the calcium will replace it in the cation balance on the soil humus and clay colloids.

Sulfur has a negative ion charge and will leach out most minerals (cations+, but not anions-) that are in excess.
Every spring if no other sulfur source is being added and sulfur is deficient, add either 250#/acre of gypsum or 50#/acre of Tiger 90 soil sulfur to supply enough sulfur for the growing season. Split spring sulfur applications into two or three smaller applications, a month apart if possible. Many types of manure and some composts are a significant source of sulfur; so take their additive effect into consideration.

Interesting side-note:  Coal-fired power plants were found to add an average of 7 #/acre sulfur to USA crop soils. Now that many coal-fired power plants are being cleaned up or are being replaced with natural gas-fired plants, sulfur deficiencies are becoming more common place in many areas.
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Sulfur test levels of 20 ppm are the minimum recommended level and around 30 ppm is ideal.

Zinc is a micro nutrient that is essential for the transformation of carbohydrates, development of new leaves, seed / fruit set and the formation of protein. Zinc should always be at a higher level than copper. (This is hard to accomplish with crops where copper is often applied as a fungicide)36% Zinc sulfate is a good form to apply. Good results can also be achieved with with zinc amino chelates.

10 lbs. of zinc sulfate per acre will raise zinc levels 1.8 ppm in a clay soil, more is needed than in a sandy soil. Don’t apply more than 40#/acre of zinc sulfate to raise levels to 7.6 ppm.
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Zinc is needed at a minimum of 4 ppm; 6 to 8 ppm is ideal and above 10 ppm is excessive. Copper is often above 10 PPM on soils where copper is used as a fungicide regularly. A foliar fed fertilizer containing zinc can be applied in situation where copper levels are above 10 ppm.

Manganese is a micro nutrient that holds and sets fruits and is vital in many other plant functions. Manganese sulfate is 23-27% manganese and it is the best form for raising soil levels.25#/acre of manganese sulfate will raise levels by 3.5ppm. Add a maximum of 200#s/acre of manganese sulfate to raise levels 28ppm.Keep Mn levels at about 80% of iron levels.
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Manganese is needed at a minimum of 15 ppm, a 30 ppm level is ideal.

​Iron is essential micro nutrient essential for the formation of chlorophyll and for photosynthesis. Iron levels always have to be higher than manganese levels; when manganese is higher than iron it will tie up the iron. Over 75% cation saturation levels of calcium will start tying up available iron. Ferrous sulfate (aka iron sulfate) is the best form to apply. (Note: Apply to foliage at low levels or it will burn the leaves and shoot tips). Ferrous sulfate will also stain concrete. Iron is rarely deficient in most soils unless the soil pH is out of range.  If a plant tissue sample comes back showing a Fe deficiency; check the soil pH first before applying any iron amendments. Use an iron chelate for foliar applications.
100#/acre ferrous sulfate will raise iron levels 10.5 ppm. Don’t apply more than 400#/acre ferrous sulfate per year to raise Fe levels 44 ppm.
Iron is needed at a minimum level of 20 ppm, over 40 ppm is ideal.

Copper is a micro nutrient and is an enzyme activator and is a catalyst for plant respiration. Copper and boron are disease fighters. Very high organic matter soils ties up copper; most severe copper deficiencies are on high (above 5%) organic matter soils. Excessive copper can effect phosphate, zinc and iron uptake.   Growers using copper-based fungicides should be aware of this effect and monitor the other nutrients closely.  

Above 10 ppm CU, plenty of phosphates are needed because copper can tie up phosphorus the same way phosphorus can tie up copper.  Excessive levels of nitrogen slows down the uptake of copper. Add no more than 10#/acre of 23% copper sulfate every six months to the soil; this will raise soil levels .6 ppm.
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 A copper level in the soil of 1.5 ppm is minimal, and levels over 4 ppm are excessive.

Boron is a micro nutrient that promotes maturity with increased set of flowers, fruit, seed, yield and quality. Boron is necessary for nitrogen conversion. Good boron levels make for good disease resistance. Boron is the only micro-nutrient that once corrected will still need to be applied every few years; as it leaches from soils. Boron is very potent and excess quantities can cause plant toxicities quickly. Apply boron carefully.

For excessive existing boron levels, raise calcium levels to optimum first and then elevate potassium. High calcium levels can block uptake of boron, but will prevent toxic effects of excessive boron. Add no more than 10# Solubor boron per acre once a year to raise levels by .2 ppm.  For fungus control keep boron levels above 1.5 ppm. (Read More)
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Boron levels of .8 ppm is the minimum, 1.5 ppm is ideal and 2 ppm is the maximum.

The acidity and alkalinity of soil is measured as pH. For the most fertile soil most crops prefer, the cation saturation is nearly balanced and the pH will fall into a range of 6.3 – 6.8. Outside this optimal pH range many nutrients start to become unavailable and soil biology is suppressed. Decay rates and conversion of organic matter is slowed and reduced.

Raising soil pH - Is not as easy as dropping some lime on it.   Rates have to be calculated (see formulas below) and a soil specialist should be consulted.  Different rates of lime and/or gypsum may be required (or a mix of both) to keep the levels of calcium, magnesium, and sodium balanced.   Too much lime applied at once or over time can cause deficiencies of other nutrients like magnesium, potassium, boron, zinc, and copper.  Gypsum is more pH neutral and will leach downward in a soil more quickly than common lime.  Ground limestone only moves downward about 1 inch per year; so it is best to incorporate it into the soil with tillage equipment.  Hydrated lime is very reactive compared to regular ground field lime and should be used with precaution.

Soil pH is commonly adjusted lower with sulfur applications.  It is important to know that sulfur applications can be very hard on fine root tips and hair feeder roots.  It would be best advised to avoid heavy sulfur soil applications during periods of active root growth.  Applying sulfur may be best done post-harvest or in multiple small applications versus a single large application.  If elemental sulfur is used as a fungicide, it contributes to the plants sulfur requirement much more than affecting soil chemistry.

​Cation Exchange Capacity is a number that represents the soils ability to hold onto and provide nutrients. A sandy soil has a C.E.C. of between 4 and 9 and cannot hold onto very many nutrients. A heavier clay soil would have a C.E.C. of over 16 and hold more nutrients than a sandy soil. The strongest nutrient holding soils have CECS in the 20’s to 30’s. CEC measures the quantity of clay and humus in a soil. By increasing the humus the CEC will increase, providing improved nutrient retention and availability.  CEC goes up 2 points for every 1% increase in organic matter.  Increasing a soil’s organic matter year over year by even 1% is difficult, and takes effort on the part of the farmer to replace or raise the amount of organic matter converted of lost in most crop fields annually.

Cation (+) Saturation

​Cation saturation is the percentage of calcium, magnesium, potassium, sodium and hydrogen held on the clay and humus sites on a soil test. The ideal calcium range would be 68% to 72%. The ideal magnesium level depends on how much sand or clay the soil contains. For sandy soil the optimum range would be 16% to 20%, and for clay soils closer to 12%. The ideal potassium range would be at least 2% and 4% to 6% is better. The ideal sodium range is at least .5% and not over 3%.

To figure desired calcium: CEC X optimum % (68%) X 400 minus existing calcium.

To figure desired magnesium: CEC X optimum % (12% to 18%) X 240 minus existing magnesium.

An example for calcium would be a soil with a CEC of 10.0, and a desired calcium percent of 68%. Change from PPM to #/acre on soil test by multiplying by 2.
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10 X .68 X 400 = 2720 lbs. of calcium. If the soil already has 2120 lbs. of calcium, 2720-2120 = 600 lbs. of calcium needed. With 600 lbs. of calcium in a ton of limestone this soil would require a ton to raise calcium levels to 68%.

​One of the best and cheapest organic fertilizers is compost. It contains organic matter, humus, calcium, phosphorus, potassium, nitrogen and many micro-nutrients, billions of microbes in each ounce and is a great food source for the biology in the soil. Compost made from plant residues and animal manures that have been fully decomposed can be applied every year at 1 to 8 tons per acre. In poor soils initial compost applications should be much higher, if the compost is fully digested and mature with a proper Carbon:Nitrogen ratio. Compost made from branches, leaves and plant residues with less manure inputs are best for hop varieties that prefer more acidic soils since this best supports fungal growth. Forests have soils that are inhabited predominantly by fungal growth. Orchard (non-tilled) soil biology closely resembles forest soil biology. Immature fresh compost containing woody residues mixed into the soil robs plants of soil nutrients (especially nitrogen). If the compost contains fresh woody residues; it is not finished and it should only be used as mulch or added to the top of the soil. Too much compost in the soil is hard for the soil to break down quickly and will temporarily tie up nutrients. If the compost has a proper C:N ratio of approx. 10-12:1, it does not tie up nutrients. High carbon composts always tie up nitrogen and sulfur, and sometimes other nutrients when worked in to the soil.  Hop varieties that prefer more alkaline soils benefit from composts containing higher ratios of manure, lime and bone meal.

Further reading and resources:

• Blog: Fall Fertilizing for Healthy Hops Plants
• ​Blog: Is Chlorine Hampering Your Hops?
• UMN - How to take a soil sample for testing video
• Fertility Guidelines for Hops in the Northeast
• Hops Fertilizer Guide
• Nutrient Deficiency Symptoms
• USDA - NCSS Soil Education Resources

​Soil compaction in the hop row from season-to-season is probably the most common problem encountered when consulting a hop yard. Many growers prep their new hopyard sites by plowing and amending the soil prior to planting but fail to do this practice in following seasons. Why? To help preserve a permanent row cover crop? Don’t have the correct and necessary equipment? Hopyards DO require specialized equipment to operate and maintain - - it is time for new hop growers to get on board with this fact.

Hops are the second fastest growing plant in the world and have to develop a massive feeder root system each season to support the amazing bine growth rate. A critical part of this hop root system is the fine fibrous feeder root system that re-forms each spring in the top 6 inches of nutrient rich topsoil. Individual feeder roots may only last for 5 to 7 days before being replaced by new ones in a continual process. The fine hair-like feeder roots spread outward from the central crown and larger permanent roots as the spring season progresses. Their function is to find all the necessary macro and micro-nutrients and transport them up the plant using lots of available water. Poor feeder root development and management translates to poor hop bine growth.

Roots only accumulate nutrients and water that come in direct contact with them. Anything that restricts a hop plant's root density results in less overall nutrient uptake. Most nutrient-collecting roots grow in the top 6 to 8 inches of soil because that’s where the microbes, nutrients, and oxygen are located. Nutrient uptake grinds to a halt if soil oxygen levels and exchange rates with the atmosphere are limited by soil compaction. It doesn’t matter if the soil test says all the soil nutrients are present and accounted for – the plant can’t take them up in sufficient quantities without the soil oxygen being present. The perfect rooting conditions are nutrient rich, well-aerated soils with adequate moisture present. This is sometimes referred to as a soil having good tilth. 

How can a compacted soil be corrected? First identify the ALL possible factors causing the compaction; then apply the best actions to correct it.

• First, determine the soil type - Clay soils are notably finer than sandy soil and have limited air pore space between the smaller soil particles compared to sandy soil types. Clays also have a strong bond between soil particles caused by high levels of magnesium. The more clay content in a soil; the higher the probability of compaction. Annual freezing frosts naturally aid in reducing shallow compaction of clay soils in northern regions. Many hop growers "hill-up" their hop rows in several stages throughout the growing season; adding additional nutrients alongside each row. The nutrients are tilled into the soil and rolled toward the row center; on top of the rooting zone. This  annual mechanical tilling practice is somewhat comparable to hilling potatoes.
  In many cases, compact heavy clay soil aeration and drainage can be improved with a gypsum amendment. Gypsum naturally loosens clay soils with high magnesium levels. (Magnesium levels determine how tight or sticky a clay soil profile is.)  Gypsum is pH neutral on soil pH levels. 
• Physical Compaction – Usually is caused by heavy tractors and other equipment in the field or working soils when they are too wet or dry. Note that most hopyard rows are spaced to accommodate tractor tire widths; so the most compaction occurs right alongside the hop rows. This can create very dense un-aerated soil conditions on both sides of the hop rows where feeder roots cannot penetrate or survive.
  The best time to work clay-content soils is when the clay crumbles in your hand. If it balls up or chalks out, it is best practice to stay out of the yard with the tillage equipment. Working hopyard soils at the wrong time has a compounding long term effect of reducing pore space > reducing oxygen> reducing microbial activity> reducing organic decomposition rates> reducing the production of soil organic acids> reducing the amount of nutrient availability> reducing plant growth rates.
  Hop plants respond best to having soil compaction removed by deep tillage done alongside the rows early in the season.  It is necessary to complete this springtime cultivation before the shallow feeder root system begins to form. If wet springtime conditions are common in your region, consider completing these deep tillage operations in the prior fall season when soil conditions may be more favorable.
  Side Note: Adding and incorporating decomposing organic matter to mineral-based soils helps raise soil levels of complex organic compounds, microbes, enzymes, and acids that increase availability of essential plant nutrients. This essential process is referred to as the humic acid cycle. It is very worthwhile to learn how this natural process makes healthier vibrant soils. 
• Striated soil pH – a condition found commonly in agricultural field soils used in the past to grow mono-crops such as corn and beans in rotation for years, where lime was surface applied. This effect is simply described as a huge variation of pH levels between the shallow topsoil and subsoil regions. (Levels of pH 7.5 topsoil /pH 4.5 subsoil are not uncommon.) Hops have both deep permanent roots and shallow annual feeder root systems. Large differences of soil pH in each plant root zone can cause a seasonal stunting effect as the hop shifts from the low pH deep root system to the high pH shallow feeder root system. Plants may emerge normally in spring using the stored nutrients of the permanent deep roots but stall after the first initial upward push; as the plant fails to transition properly to the feeder root system. It results in stalled growth in severe cases and resembles transplant shock. Ideally this soil pH issue is identified by testing prior to establishing a hopyard.  Deep 18"-24" subsoil tillage can be done to help mix and break up the different pH layers. 
• Hardpan- is a compacted field soil condition that form 12 to 18 inches below the soil surface from years of continuous shallow tillage for other crops. This compact layer stops deep rooted hop plants from establishing deep into the soil and limits deep root mass.  The corrective treatment for hardpan is the same as for striated pH above. In practice, it is best to do deep plowing and subsoil tillage prior to establishing the hop yard.

The majority of commercial hop varieties prefer a slightly acidic soil. A soil pH of 6.2 to 6.8 works well for most hop types (there’s always exceptions). Soil pH in a nutshell, is simply a method of measuring soil acidity or alkalinity levels by measuring the electrical charges present. All soil minerals and nutrients carry either positive (cations+) or negative (anions-). Many are metallic - Iron, Zinc, Copper, Boron, Magnesium, Manganese, and so forth. When a soil pH is in electrical balance all the different nutrients are available. When it is too high(+) or too low(-), many different nutrients and processes are blocked and nutrients become less available to the plant. (Root surfaces also have electrically charged sites that match up with the different charged nutrients- kind of like a matched lock and key system). Improper soil pH slows down microbial activity and organic matter decomposition rates. A wrong soil pH coupled with the soil compaction cascade effect described above is a real growth killer. This is a very common issue in hopyards experiencing poor overall growth.

Irrigation is a lot more complex than most growers realize. Hops have both shallow and deep root systems and it is the shallow root system in the top 6 inches of topsoil that is responsible for most of the nutrient and water uptake during the short formative high growth phases of climbing the trellis and forming sidearms/cones. Most hopyards employ drip irrigation to deliver both water and supplemental plant nutrients. Choosing the right irrigation system design; how it is installed and operated are important issues. Here are a few of the common mistakes we have seen growers make.

• Mismatched drip lines to water supply pressures and gallons delivered per hour by the water source. If the pump or well cannot support the flow rate required by the drip lines and row lengths, then drip line pressures are compromised and water delivery is uneven. A common visual symptom is that the hops get smaller the farther they are from the water source.

Many hop growers do not realize the value of accurate and timely testing of their soils in their hopyards. The goal of all soil testing is to inform the grower of what nutrients are available at the beginning of the growing season; middle of the season, and what is left at the end of the season.  These test help identify nutritional problems before they cause problems and what needs to be replaced or amended.  It is strongly advised for inexperienced new growers to do testing three times during the season.  A complete soil test includes soil pH, alkalinity, organic matter, macro elements, microelements, cation exchange capacity (CEC), and cation saturation. A foliar test should also show the complete range of elements; not just N-P-K levels.

• Hops require different levels and balances of nutrients at different growth stages during the season. For example: Phosphorus is critically important in early spring for new root development; at burr onset; and rebuilding energy going into winter.  Nitrogen is essential during the climbing and side arm development stage; but not during cone maturation or during preparation for winter dormancy. Extra zinc and boron are specifically required at burr initiation.
• Spring testing: Shows what the general levels are of all nutrients and soil pH going into the season. Do this test before the first major round of spring hopyard cultivation. This allows time to incorporate  slow-acting amendments like lime, sulfur, or gypsum.
• Mid-season FOLIAR testing: do this preemptive test just prior to bine sidearm initiation.  The goal is to identify if the essential nutrients like potassium, zinc, and boron are being taken up in sufficient quantities to set burrs and cones for maximum yields.  If the foliar test shows deficiencies there is still time for quick corrective amendments or foliar fed nutrients to save the day. Compare the foliar test results to the last soil test to determine if there is a deficiency in the soil or if there is a nutritional imbalance that is causing plant uptake issues.
• Post-harvest soil testing: Shows what nutrients were removed by the hop crop and losses to leaching, and what needs to be replaced going into winter dormancy.  Specifically check the N-P-K levels, sulfur and organic matter content. If soil pH or compactions are identified as issues, early fall is a good time to apply corrective amendments like phosphate, potassium, lime, and gypsum. 

For more information on soil testing, please find a text book like "The Basics of Understanding Soil Fertility and Soil Testing" or consult  with professional grower services and suppliers.

Selecting and applying the right combination of fertilizers is a definite grower skill.  It requires knowing the soil profile/pH, the irrigation water quality, the individual hop varieties, understanding soil/foliar tests, and some pretty complex nutrient interactions. Successful hop growers find that applying a combined program of organic, granular, and drip line fed soluble fertilizers at appropriate times of the growing season is the most successful. Hops have high uptake requirements for many micronutrients besides the major N-P-K elements. If any of the minor elements are deficient, hop growth is compromised. Many growers use additional foliar-fed fertilizers with micronutrients at key stages of hop growth as insurance against having a micronutrient deficiency. Here are a few common fertilizer issues that have been encountered.

• Surface application of nutrients vs. deep spring tillage with incorporation of new nutrients. Applying replacement nutrients year-after-year to the soil surface without tilling/incorporation creates a very shallow root system.  (In hopyards using weed control mat, the root system can actually be right at the soil surface.)  Early spring deep soil cultivation done as the hops emerge to ensure a deeper nutrient-rich rooting bed. This is desirable because hops with deeper root systems can handle adverse growing conditions such as heat-stress and drought far better than shallow rooted plants.  Deep tilling on either side of the hop row has to be done early in the season, before the new shallow feeder roots form.  Deep tilling close to the plants after the hops are 4 to 5 feet tall is counter-productive because of the amount of damage to the feeder root system forming around each plant. Incorporating granular soil amendments during later stages of plant growth is done by rolling soil from farther out in the aisle towards the row without disturbing the soil right next to the plants.

• Selecting the wrong nitrogen source for the time of the season.  Most fertilizers containing nitrogen are formulated with two types: nitrate and/or urea.  Both are water soluble sources of nitrogen but nitrates can be used more directly by the plants, while urea has to be converted by microbes first.  Either nitrogen source if over-applied can cause disease outbreaks and inhibit uptake of other nutrients like zinc and copper.  Synthetic nitrogen fertilizers also lower levels and burn out existing beneficial soil microbes and lead to increased soil compaction. Urea applied early in the season before the hop feeder roots form is often of little use to the hop plants because - 1.) High leaching rates and 2.) The soil microbes that convert urea are relatively inactive in the cold soil conditions. 3.) Urea applied to cold saturated soils will convert to ammonia; which will burn back any new roots. It is better to wait and apply urea formulated fertilizers after the soil temps rise into the 60’s and the soil biology is more active. A better set of choices is to first apply a jumpstart low level of organic fertilizer or manure to increase microbial soil activity that can then break down the later-applied urea more efficiently, or apply nitrate-based fertilizer  that the plants can utilize without microbial conversion. The emerging first flush of spring hop growth primarily utilizes energy stored as sugars and carbohydrates in the overwintering deep roots until the hops reach a height of about 6 to 8 feet. At the point where the stored energy has been depleted, the newly formed shallow feeder root system takes over collection of new nutrients to push bine growth up the string to the top. This transition from one root system to another is what makes the difference between hops that reach the top wire and hops that stall growth at 10 to 12 feet.

Some growers have also found an incorporated granular application of a sulfur-coated urea (SCU) applied after the hops are about a foot high to be beneficial.  The sulfur coating meters the urea release, reducing leaching and ammonification, and also has some beneficial fungicidal effects. Applying liquid organic humates as soil drenches or via drip line injection in early season is also beneficial in many mineral-type soils with low organic content to help release  bound soil nutrients from soil particles.

• Selecting the wrong N-P-K and micronutrient package in the fertilizer formulation.  Selecting the right mix of nutrients can only be done after analyzing a complete soil and water test that includes organic matter content and the micro elements.  Examples:  Applying a calcium-based fertilizer when soil Ca levels are already high and magnesium levels are low;  or having too much or too little Boron. See the GLH soil fertility blog for more info about interpreting soil tests or consult a professional agricultural crop specialist in your area.
• Applying a fertilizer directly to the hop crown. A recipe for a disease outbreak.  The roots are not located there.  Always apply fertilizers around the hop plant. Having high excess nitrogen levels in the hop crown region any time of the year is bad cultural practice.

Hops are like a big nutrient-sucking vacuum cleaner.  The shallow feeder root system is very dense and very efficient at scavenging all the nutrients from the surrounding topsoil.  Each year the hop crown grows larger and requires more nutrients than the year before.  Only by limiting the size of the crown and root structure in mature hopyards can overall nutrient needs be stabilized.  In the wild, hops deplete soil in one area and physically move to new areas via long, spreading rhizomes. Replacing the depleted nutrients removed each season from the hopyard soil is a major challenge for hop growers. Growers should have a complete post-harvest soil test done to see what the real rates of nutrient depletion are. It is best practice to apply soil amendments in several smaller applications versus a single bulk application each season. This avoids the potential of blocking balanced uptake of other nutrients. 
Ongoing annual replacement of nutrients should be considered a year-around continuous effort.  The goal is threefold : 1.)To replace the depleted nutrients with balanced long term sources; rather than reactive quick fixes. 2.) To increase the nutrient holding capacity of the soil. (CEC)  3.) To rebuild soil organic matter and increase soil microbial activity to improve nutrient conversion and efficiency. Both are essential to the humic acid  cycle and good soil tilth.
Many soil and plant processes are interdependent on the balance of nutrients in the soil and plant. Too much of one nutrient will block uptake of another. Too little of another element will stop a complex conversion process.  It is easy to mess this natural balance up. Here are a few things to avoid.

• Do not feed hops only with synthetic fertilizers – granular and / or water soluble.  It is well documented that using only synthetic fertilizers will reduce and destroy the soil microbe levels necessary to efficiently convert nutrients to forms usable by plants.  Hop growers are faced with having to use high levels of synthetic N-P-K fertilizers during high growth stages to get maximum yields. Pure organic fertilizers simply cannot provide quickly enough the the high level of nitrogen hops demand during the climbing and coning phases of development. This creates a situation where often very high relative levels of synthetic fertilizers are being applied continuously long term to a hopyard soil during peak growth periods. The potential for soil organic matter burn out and reduced microbial activity is large. This leads to breakdown in the humic acid cycle, soil compaction and reduced nutrient availability issues.

The best management practice is to use a mixed approach to hopyard fertility. Use organic fertilizers whenever possible to help rebuild the soil organic matter and microbe levels. A set of good practices is to apply incorporated manures early spring and/or postharvest; with annual aisle cover crops to build biomass during the growing season. Here are a couple of tips to get it right:

• Avoid over-applying fertilizers, composts, and manures in one big shot.  Soil microbes can only handle just so much at a time and large excess quantities can slow, block, or even damage soils and nutrient availability.  Large percentages of nutrients are lost to leaching and volatilization and may end up in nearby surface waters. Plants can use nutrients far more efficiently if they are applied in multiple applications. Be a good steward of the land.
• Using the wrong fertilizer placement.  Some nutrients like phosphorus and lime do not percolate readily down into the soil profile and need to be incorporated to be dispersed, available and effective.  Granular fertilizers containing urea should be incorporated immediately after application or large amounts are lost to volatilization. Again, never apply fertilizers directly over the hop crowns. High excess nitrogen levels in the hop crown encourage disease outbreaks.  Always apply fertilizers around or alongside the hop crowns.
  
  Since most of the soil nutrient depletion occurs in the hop row, this is where nutrients need to be monitored and replaced annually. A common set of seasonal practices  to prepare the hop rows would be:

1. Plow/disc back 6 to 8 inches deep on both sides of the row in early spring (or late fall) while the plants are still dormant; to roll away the depleted topsoil into the aisle way. This has to be done very early; before the shallow fibrous hop feeder roots begins its growth for the season.  A sharp disc or plow/coulter combination is commonly used to cleanly cut any rhizomes free from the crown at the same time.  The cut rhizomes are then removed from the hop yard.  A shallow trench has now been created on each side of the remaining 12-14" center row.
2. The remaining center row strip is next topped or trimmed tightly to the ground when the first bull shoots emerge and prior to the second flush of bines.  These first shoots, weeds, and old dead bines is removed; leaving a clean weed-free center row. This debris will later be incorporated and buried when fresh nutrient-amended soil is rolled back against the row.
3. The depleted rolled back row soil (now in located in the aisle) is then amended with all the necessary replacement nutrients, compost, manure, etc. to recharge it.  This freshly-charged soil  is thoroughly mixed using a disc and is rolled back towards the hop row; eliminating the trenches made in step one.  This creates a nice aerated  uncompacted soil rooting bed full of new nutrients for the hop feeder roots to form in for the coming growing season.  
4. The hops are next strung and trained as soon as the bines start showing a hooking twist at the tips.  Another light shallow soil cultivation operation is done after bine training to remove any new compaction caused by training activities.
5. As the early season progresses, the aisle ways between the hop rows are periodically tilled when seedling weeds reach 2 to 4 inches in height. (Always till before any weeds are mature enough to set seed.)  Each time a hop yard cultivation occurs, more aisle soil is thrown against the hop rows to smother new emerging weeds and incorporate any banded fertilizer applications. This continues adding fresh nutrients and fresh loose aerated soil to the rooting bed as hop growth accelerates into the growing season.
6. Some growers then overseed the aisles with annual cover crops such as a combination of buckwheat, rapeseed, and field radish for the rest of the season to help smother late-emerging weeds.  These annual cover crops also function to keep the yard cooler during the hottest months of the year and to help maintain the soil organic matter content.  Most annual cover crops grow quite tall and should be mowed shorter (6") when cooler, wetter  fall weather conditions  return/occur.

​Hops produce shallow underground budded runners called rhizomes.  These are not roots. (Hop roots are white and do not have latent buds).  Rhizomes naturally function to allow a hop plant to continually spread outward in the wild; searching for favorable locations to re-establish.  In commercial cultivation of hops these  unwanted rhizomes have to be removed annually or semi-annually to keep the hop plants from spreading into the aisles.   If the rhizomes are not removed, they divert energy from the crown and the climbing bines, resulting in lower yields of hop cones. The hopyard tillage steps described above are recommended for timely early spring/ late fall rhizome removal.

Hops annually form a dense shallow feeder root mat structure as the growing season progresses.  It forms in the top 6 to 8 inches of soil.  This feeder root system is responsible for absorbing all the water and nutrients required to push the hop up the twine once the permanent deep roots have exhausted their stored sugars and carbohydrates used for spring emergence.  Tilling too close, too deep, or at the wrong time can severely stunt the growth of hops. Here are some tips.

• ​Complete all deep cultivation of soil adjacent to the hop rows before hops reach 1 foot tall. The new feeder roots are not formed yet, so soil cultivation can go deep and close to the crowns.  Most growers maintain about an 14-18 inch row width. Rhizomes are removed during this operation, also. The soil is rolled away from the hop row,  cutting and exposing the unwanted rhizomes.

Many fungicides applied to hopyards contain metallic compounds, oxidizers, and acids that affect plant nutrition. Here are a couple of the common interactions encountered.

• Copper toxicities and nutrient blocking from over application of copper-based fungicides. Excess copper sprays and soil drenches can effect phosphate, zinc, and iron uptake and create deficiencies.  Know your soil copper levels before adding more. Zinc levels should always be higher than copper levels. Beware that repeated heavy copper foliar sprays prior to and during burr initiation can create temporary zinc and phosphorus deficiencies and reduce total cone set and yields. A case of petting the puppy to death.
• Using phosphites (also known as phosphorus acids) as replacement for phosphate fertilizers.  These products sound like they both supply phosphorus but they are quite different.  Phosphites have a biocidal and fungicidal effect and are properly labelled and used as fungicides; not fertilizers.  Phosphites compete directly with phosphates and are taken up equally by plants. However, phosphites break down very slowly in a plant and occupy sites in the plant cells that ordinarily use phosphorus. This limits all the important functions that phosphorus plays in plant growth.  In short, when using phosphites be certain that adequate phosphate is present to maintain a proper balance between phosphites and phosphorus to avoid a deficiency.  Never substitute a “fertilizer” containing phosphites for a true phosphate fertilizer.  Having adequate phosphate present also goes for when phosphite drenches are used in the spring for downy mildew control. Adequate phosphorus availability at this time is crucial for new root development.
• Using phosphites POST-HARVEST  in hopyards with existing downy mildew infection seems promising. Downy mildews move into the hop roots, crowns, and buds to over-winter.  Phosphites are somewhat unique in that they will translocate downward in plant tissues and roots.  To be most effective they should be applied as a drench relatively soon after harvest is complete.   Phosphite takes 3 to 4 months to slowly break down completely, and has good downy mildew fungicidal and protective properties; so a post-harvest drench application could potentially provide effective downy mildew protection through the fall, winter, and even into early spring.  Time the application before the hops enter dormancy or preventative control will be limited in value. 

Plant nutrients and soil particles carry specific electrical charges and nutrient availability for plant uptake is a complex interactive process, to say the least.  There is a wealth of technical information on the subject of plant nutrition and it would take a Rhoades scholar to interpret it all.  Here are a few of the interactions that have been identified. Use this information to help spot potential out of balance issues in soil and foliar tests.

• Decomposition of organic matter by biological activity releases organic acids and enzymes that interact with soil colloidal particles to release available nutrients. This is commonly referred to as the humic acid cycle.  Levels of organic matter decline annually in cultivated field soils and it is a challenge simply to maintain and replace organic matter levels depleted each season.  Without organic matter biological activity grinds to a halt and nutrient availability drops off.
• Compacted soils create anerobic low oxygen soil conditions and microbial activity is  reduced and nutrient uptake is then also restricted. High levels of synthetic fertilizer salts are a major contributor to soil compaction.
• Phosphorus availability is restricted by lower soil pH combined with high level of soil aluminum, iron, and zinc.  Excess phosphorus blocks zinc and copper uptake in hops. This is a very common imbalance in agricultural field soil tests. 
• Potassium can be blocked by excess soil calcium, magnesium, and sodium levels. Excess potassium blocks boron, calcium, and manganese.
• Calcium in general will loosen most soils and make nitrogen more available. Excess calcium can block about every other nutrient; especially magnesium, potassium, boron, zinc, and copper.
• High Sodium levels in soils and irrigation water create toxicities in dry arid soils by reducing biological activity and reducing water uptake by roots. High sodium levels combined with high potassium levels blocks manganese availability. Soil compaction levels can become severe.
• Nitrogen availability is limited any time soil microbial activity is reduced. Excess nitrogen can induce zinc, sulfur, and copper deficiencies; burn out organic matter and soil microbes. Nitrogen and sulfur combine to leach out calcium. Out of balance excess nitrogen is common in hopyards due to the high application rates.
• Sulfur aids in microbial decomposition of organic matter. Sulfur combines with and leaches out excess calcium and magnesium. Excess sulfur creates a lowering of soil pH and can burn root tips.  Sulfur also has a fungicidal effect.  
• Zinc is an important micronutrient in growing hops. Zinc levels should always be higher than copper levels. (Harder to do than thought if copper-based fungicides are used frequently.)
• Manganese helps set and hold hop cones.​ Excess manganese blocks iron uptake if iron soil levels are low. Cones shatter at harvest> check MN levels
• Iron rapidly becomes unavailable at high soil pH levels.  Wet, cold soils often create iron deficiencies. Nutrients bind tightly to deep soil colloids containing high iron.  Organic acids (humates) and enzymes produced by biological activity in the topsoil leach down into the deeper soil profile and make these nutrients soluble again.  Thus organic matter content in the topsoil is critical for deeper nutrient availability.
• Copper (and boron) are disease fighters. Soil types with organic matter above 5% can have copper deficiencies. Excess copper affects zinc, phosphorus, and iron uptake.
• Boron is necessary for optimal nitrogen conversion. It leaches easily and needs to be replaced in most hopyards annually. Brittle hop bine tips that break easily during training are an early sign of a possible B deficiency. However caution applying corrective boron as it can easily be over applied to toxic levels.

Cover crops are making a comeback in agriculture. Annual cover crops are used in agriculture and hopyards to:

• Scavenge nutrients using deep rooted cover crops such as field radish. Immobile minerals like phosphorus are moved deeper into the soil profile when the cover crop is tilled under and leaves stems and roots decompose.  Deep-rooted Daikon field radish used as a cover crop is a perfect example of this.
• Increase soil organic matter and biological activity. Just like above, the cover crop has to be tilled under to be beneficial. This practice aids in replacing depleted organic matter lost each growing season. Humic acids are produced.
• Provide beneficial effects against plant pathogens.  Plowed under barley residue has beneficial fungicidal effects. Yellow mustard breaks down into a natural nematicide when tilled under. Biodiversity in the hopyard is enhanced.

There are complete books written on this subject and it is best to defer to them, rather than rewrite them here. However, here are a few things hop growers need to know that may not be clearly presented in books as it pertains to hops production:

• Many hop fungal pathogens require wet leaves or saturated soils to flourish.  Don’t help them develop by creating prolonged wet leaf conditions or overly wet saturated soils.  There is an old grower saying: “Don’t send plants to bed wet”.  Ideally, leaves and surface soils are not wet during night time hours.  Saturated soil does not necessarily mean the whole field.  Drip irrigation system operations and schedules that create continuous wet saturation zones around the hop roots is simply asking for trouble.
• Foliar infection and spread of mildews should be thought of as a two-event process.  Foliar leaf infection occurs at a first event where the moisture level duration is long enough to allow spore germination. This initial spore infection process is invisible to the naked eye.  The initial infection develops and colonizes the host. A second moisture event causes the mature fungal colonies to reproduce a new generation of spores (now suddenly very visible); where upon the hop grower goes into full panic mode. Repeated curative controls are the only remedy and the damage is irreversible. The key is to apply preventative protective controls before the first moisture event to prevent the initial infection. This means watching the weather forecasts closely to know when the right "wet leaf" conditions are predicted.
• Downy mildews follow the sugar. Seasonally, downy mildew tends to invade the parts of the hop plants with the highest sugar and carbohydrate content.  In the spring it is the new hop shoots; during summer it is hop leaves, at harvest it is cones, in the fall it is crowns, roots, and newly-formed buds.  Scout and apply preventative controls to these locations early in anticipation of pathogen infection.

In many regions dormant hop crowns left exposed during the winter months suffer crown and bud damage and loss to winter freeze-thaw cycles and desiccation.  The fix is simple – cover them with a shallow layer of field soil a minimum of 1 to 2 inches deep. This will act as a buffer against freeze-thaw cycles and provides moisture to prevent bud desiccation.  Hop growers that hill the hop rows during the season are automatically covered by this practice.

• It is a good practice to apply some high potassium fertilizer post-harvest.  It will improve disease resistance and help provide protection from freeze damage during the winter.
• Do not cover dormant hop crowns with heavy wet mulches or manures.  This will cause crown rot to set in and very high losses of plants can occur.
• Set new plantings of hop transplants deeply enough to cover the crown. ​Exposed crowns can also be pushed up by frost cycles in some soil types.
  

Hops in general, prefer slightly acidic, well-drained sandy loam soils pH 6.2 -6.8. The farther the site’s soil deviates from this, the harder hops will be to grow and suitable hop cultivar selection will be narrowed.

• If a hopyard is planned for a site that had exposure to Atrazine herbicide (think old cornfields) a deep subsoil test should be done prior to proceeding any further.  There is no cure for residual atrazine as its half-life is 25 years or more.  Hops have deep permanent roots that can take up atrazine found locked in deep soil profiles and hardpans. (Don’t confuse the annual shallow feeder root mat with deep permanent mineral roots. Hops have both.)
• Fields with seasonal water tables higher than 18 inches below the surface are poor hopyard sites.  Hops have deep root systems.   These sites will require field tiling.
• Old alfalfa fields can carry levels of Verticillium.  This hop pathogen has no controls and kills certain varieties of susceptible hops. 
• Old orchard ground can harbor nematodes, garden symphylans, and Armillaria / Verticillium root rots. Old decaying tree roots harbor these pests and pathogens. 

Mulches and composts are different from each other.  Mulches are surface applied organic matter that may not be decomposed.  Examples would be leaves, wood chips, shredded bark, alfalfa hay, straw, and etcetera.  Composts are fully decomposed forms of mulches and manures with a stable carbon to nitrogen ratio.  Properly prepared composts go thru a high temperature phase which kills harmful pathogens and weed seeds.  Mulches do not and can be sources of pathogen if not selected carefully.

• Mulches suck up available nitrogen as they decompose.  Extra nitrogen has to be applied to compensate. Wood chips in particular remove a lot of nitrogen.
• Composts originating from woody products are more beneficial for acid loving hop varieties. The woody matter encourages the types of beneficial soil fungi species these hops prefer. Hops with German heritage would be included.
• Composts originating from poultry manures are beneficial for building poor sandy mineral soil and hops that prefer more neutral or higher soil pH levels. Hops with English heritage do well on soils amended with poultry manure.
• Some compost products, like fresh mushroom compost, can have excessively high levels of unwanted salts.  These salts can add to soil compaction issues, block other nutrients, and damage sensitive hop feeder roots.  Check composts for levels of salts, and age or leach accordingly.
• Wood chips derived from diseased deciduous trees such as oaks and maples can carry infective Verticillium and other hop pathogens.  It is advised not to use coarse hardwood chips or bark in a hopyard unless they are fully composted.  Pine bark, needles, and wood chips are OK to use because they contain terpene compounds which these pathogens cannot survive in.
• Do not place heavy deep layers of mulch or compost over hop crowns. Put it around the plants.
• Heavy application of mulches can slow down soil microbial activity.
• Heavy surface applications of mulch can serve as hiding places for pests.  Slugs, symphylans, and weevils in particular.
• Don’t use plastic mulch covers in a commercial hopyard.  The reasons why were described earlier in the weed management discussion points.
• Do not apply any harvest bine waste back into the hopyard unless it is fully composted and incorporated into the soil after application.  Hop pathogens and pests can reside and overwinter in hop harvest waste.  Do not let hopyard waste linger at a hopyard site.  Either compost the waste pile or remove it from the site.

This is a topic with much discussion amongst new hop growers. There are several points to be made and the final benefits are still being debated. In regions like the Pacific Northwest where spring may begin in late February and bine training dates are not until mid-May,  the hopyards may be mowed several times to keep bine growth under control. The debate is about if hop growers in other regions with shorter spring times would have any benefits from mowing hops once more before training; or if the recovery time left before cone initiation is too short.


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• In the spring, removing the first early emerging hop shoots is often practiced.  (Do not confuse this field operation with later mowing hops again to achieve a particular training date). These early “bull “shoots are not the best bines to train and are removed by cutting them just above the crown structure and remaining secondary buds. This practice also removes any early mildew infected shoots.  Growers using a hilling practice find that the hop crowns form more upright shoots and shorter rhizome structure.  This results in denser, tighter crowns with easier rhizome control and more selectable bines closer to the string for training.
• In hopyards where row hilling practices are not used the rows are simply mowed when the first shoots are about a foot high.  This is timed by variety; as some hop varieties emerge much sooner than others.  In general, it is noted that early maturity varieties tend to emerge before later-maturing types.
• In hop rows that use soil-hilling practices, as the first bull shoots emerge from the top of last season’s hill; the grower has to dig down and determine how much of the dirt hill and shoots can be removed without scalping the hop crown structure off.   If too much of the hop crown is removed, only roots will remain and the hops will not re-sprout unless deeper stray rhizomes are left. Most growers using the row hilling technique set the carping (cutting) height about 1 inch above the crown bud height.  Experienced hop growers often plant new hop acreage with the new hop crowns lower than surrounding field height to ensure the crowns cannot be accidentally scalped off during the spring preparation of the hop rows.
• It takes between four to six weeks for a cut hop to recover and regrow the 12 internode leaf sets needed to accept the long day length signal that initiates burr formation. If another mowing to set a specific bine training date is done later than four weeks prior to the summer solstice, (when day lengths start getting shorter); there is a risk some hop varieties will not form a full potential amount of cones.  Some hop varieties initiate burrs early in the season, and others initiate late.  In general, the later the maturity date; the later the cutting date can be. Cutting early maturing types too close to the solstice of results in little or no cones being produced. There is no concise information currently available to help determine best mowing and training dates for many hop varieties grown outside the Pacific Northwest region.  In the PNW states, large blocks of hops are often trimmed sequentially to stagger harvesting dates.  This helps spread out the hop harvest by keeping too many acres of hops from becoming ripe simultaneously and overwhelming the picking and oasting equipment.
• Some hop varieties should not be cut multiple times.  Older noble-type hops (Saaz, Hallertauer, Goldings, etc.) are not vigorous enough to recover quickly enough to meet cone initiation dates. These older varieties also tend to be less tolerating of high temperatures during cone set and will shut down during hot weather. Late cutting dates tend to move the cone initiation into later summer with little or no cones being produced.   In general; the newer hybrid hops are much more vigorous and recover much more quickly. Cutting dates a week apart on a vigorous hop variety will stagger the harvest maturity dates by an average of 10 days to two weeks.
• At harvest time cut the mature hop bines off at about a two to three foot height. Leave the remaining bine to die back naturally and be killed by frosts. This will allow carbohydrates and sugars to translocate down into the hop crown and strengthen it.  Once the bines have died back completely in late fall they can then be cut shorter or left until spring cleanup. Cutting the older noble-type hops too low, or before the sugars have translocated to the roots will cause following seasonal loss of vigor and gradual decline. Noble hop varieties like Saaz and Star can be killed within 3 or 4 seasons with improper post- harvest care practices.

Downy mildew, like most molds and mildews, persists and spreads during the growing season mainly through air-borne spores which infect new leaves and growth whenever environmental conditions are favorable.  In the Fall season, however, downy mildew “morphs” into a different creature; producing a specialized motile spore type called a zoospore.  This spore acts much more like a living microscopic worm than a fungal spore. The motile zoospore form helps downy mildew complete its annual life cycle by finding a safe resting place for it to overwinter or by forming protective dormant oospores. These forms of DM exist outside of the plant in the soil  where it is outside its host and can be interrupted at this point.

 As the hop and tree leaves color up and drop into the fall season; an alternate motile zoospore form develops and actively “swims” through wet saturated soil, very much like a nematode, searching for new hop roots and rhizomes to infect. Most of this activity occurs in the top 3 or 4 inches of topsoil. Upon contact with hop roots or rhizomes, the zoospore penetrates into the hop tissue and travels upward through the plant tissues to the newly-forming crown buds. There it will persist and go dormant for the winter. When springtime arrives and the buds loosen, DM returns to an active state; emerging with the first flush of hop growth as white spore-laden shoots; starting another seasonal cycle of aerial downy mildew infection.

A weak link and the point where downy mildew is susceptible to Fall controls is when  its zoospores are present and active in the soil. This DM phase occurs roughly from after cone harvest until all top foliage growth has yellowed on the the cut bines into late Fall. This phase also coincides with the hops forming the new crown buds during September  through October. Keeping the hop plant protected from re-infection during this time period results in lower levels of emerging infected spikes next spring.

• Simple mechanical cultivation that aerates the top 3 or 4 inches of topsoil  reduces the amount of  motile zoospores. This motile form depends on wet saturated soil conditions to survive, so any practice that aids in drying and  reducing excess soil water levels is helpful.

• Application of manures to hopyards has been shown to reduce downy mildew levels. Manures promote a vital healthy soil biome of bacteria, fungi, and microbes. Some of these are organisms that destroy zoospores. (However, do not apply fresh manure directly over the hop crown – this excess nitrogen source can cause outbreaks of other hop pathogens like crown rot and fusarium.)

•  Spot drench application of phosphonic acids (Phostrol, Fosphite, K-Phite and others) directly on infected or susceptible plant crowns.   apply enough solution to soak at least 1 inch into the soil.   Phosphite products destroy zoospores on contact in the soil and are also translocated in the plant tissue. Phosphites are are one of the few chemical classes that translocate downward in plants; protecting roots. Caution: phosphonic acid is not the same as phosphoric acid! Read and follow label instructions. Most phosphites have a long residual effect.  Earlier post-harvest applications are more effective than late fall treatments.  Treatments applied after hops enter dormancy are not effective.

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Application timing is critical for this to work!! - the longer the hops are exposed in the Fall to wet, saturated / compacted soil conditions the higher the level of disease to expect the following spring. If fields are too wet to cultivate, then at the  minimum get the fungicides applied as partial protection.

 * Tanos fungicide is a curative SYSTEMIC fungicide that will absorb into the hop plant and kill downy mildew mycelia inside the leaves and stems and stops sporulation. (Pristine or Presido can substitute.)

Notes: Don’t procrastinate with the fungicide application! If the zoospore is successful in making it to the crown bud... game over. Nothing can touch it until Springtime when it emerges  from dormancy. Fungicides have to be applied before the plants are dormant or they will not take up and translocate the fungicide. 

ORGANIC GROWER? Your best controls are the use of clean row cultivation and sanitation, good soil aeration, and drench application of organic bio-controls like Serenade and Sonata. Grass aisles can increase the severity of downy in your yards by about 30%, according to research done out west. Organic growers should also minimize their risks by avoiding planting hop varieties with known low resistance to downy mildew. Some cultivars to avoid would be the Columbus, Zeus, Centennial, Cashmere, Horizon, Sterling, & Glacier. English hops, or crosses with them, seem to have the best natural resistance to downy mildew.

Further Reading:

Hops Handbook, pg.10

Control of Downy Mildew of Hops (WSU)

Originally posted 09/15/2013. Updated 09/13/2014

This grower blog deals only with the post-harvest practices in traditional commercial hopyards and some best practice strategies to control and reduce the percentage of overwintering DM and other pathogens.  Great Lakes Hops uses these combined practices and has found them to be very effective in the Midwest region hop production.
Control of downy mildew (DM) in the hopyard is an ongoing challenge for growers in many regions; and especially difficult for growers that have susceptible hop varieties.  DM takes different forms and produces several different spore types in reaction to environmental conditions - i.e. aerial, oospores, and zoospores. Each spore type has its own set of specific control measures. DM is active whenever temperature and moisture conditions are correct; spring, summer, and fall. In the fall season, downy mildew switches from actively producing airborne spores that mainly affect the bines, foliage, and cones; to forming protective oospores and motile zoospores that can overwinter in the soil and dormant hop crown. The more familiar springtime DM spikes on new shoots are less evident in the fall as hop growth slows and the infected older foliage takes on a mottled appearance; which many growers fail to notice. Once DM has a foothold in a hopyard, outside airborne spores are not necessary to re-start early springtime infections. 

​Great Lakes Hops has found the following fall practices to be effective in gaining good control over downy mildew and other pests and pathogens in hopyards.

1.  Not all hop cultivars are treated and maintained for virus removal due to lack of commercial use and the lengthy time and expense involved to remove viruses. Newer popular hop cultivars have higher priority to be treated for virus removal in the USDA program. Older hop cultivars considered no longer commercially important are typically only virus indexed. This distinction means potential propagation stock with known virus loads are only tested for different viruses and identified - not necessarily removed or treated. This plant material is referred to as virus indexed stock.  Indexed hop stock is be replaced by virus-treated stock if cleaner versions becomes available to GLH.
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2.  Even the most popular individual hop cultivars are only retreated for virus removal every 5 to 8 years.  If it is determined that the hop cultivar is still commercially important and the viruses have re-accumulated to a level that warrants re-treatment. (See the USDA National Clean Plant Program for their detailed program specifications and methods.) GLH's role as a propagator of hop stock is to maintain and multiply larger numbers of these USDA obtain hop cultivars to commercial hopyards using the cleanest propagation methods available. It takes GLH two full seasons to propagate and ramp up to commercially available quantities of the newly acquired USDA mother stock. It is a very specialized process, and is little appreciated unless you are a fellow propagator who has created thousands of replicate plants from a single mother plant. 

3.  Any "virus free" claims made by any other hop propagation/nursery suppliers are misleading in our opinion and the term is only directly applicable to the original mother stock plant obtained directly from the USDA program. This is due to how quickly easily hop re-acquire viruses. Even the USDA program does not warranty or certify the individual nuclear mother hop plants provided remain virus free once they leave their lab facilities. It is now known that viruses may survive the virus removal treatment and may still be present a low levels that are not detectable by current virus testing methods. These latent viruses rebuild to detectable levels over a period of several months.

GLH produces cloned hop transplants that originated from these limited USDA mother plants and the resulting transplants may be tagged to show this origination. This tag identification is in no way, shape, or form indicative that these cloned transplants are certified or re-tested individually to be "virus-free". 

4.  All life forms accumulate viruses/ viroids and other pathogens – that is the reality of nature. Viruses/viroids accumulate naturally in plants over time; therefore the effort to monitor and replace heavily virus infected plants in commercial hop cultivation is a continually ongoing effort. Yes- even "clean" plants naturally re-acquire viruses and that is why they have to be continually refreshed as years pass.  Note that plants also contain beneficial virus/ viroids that may be removed by the non-selective removal treatment process. Most virus tests are also nonspecific and only indicate possible virus/ viroid groups or classes.

5.  Hopyard plant populations rarely show uniform virus expression.  In large commercial hop yards; virus expression is quite sporadic and often will often not be visible unless plants are  stressed by other factors.  Large commercial hopyards routinely rouge out individual weak plants that express heavy virus symptoms and replace them with rhizomes from other plants in the same field.  This is a normal grower practice and is similar to how virus levels are managed  in many other perennial crops.
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6.  Worries over viruses in hopyards have been overblown, in our opinion.  Over the past decade, GLH has repeatedly tested  rhizomes sourced from numerous huge PNW hopyards.  We have yet to find one sample that tested negative for viruses from these sources. These hopyards are aware of the numerous viruses and viroids present and yet are very successful at growing and providing the majority of the hops used worldwide. 

New inexperienced growers often over-react when their hopyards test positive for viruses. The immediate conclusion is that having viruses means they are doomed to failure and all the plants need to be immediately destroyed. This is a false flag because the vast majority of all established commercial hopyards in the world contain the same viruses and viroids. New hop growers should realize that hundreds of other hopyards are growing the same plant material cloned from the same original female plant and are very successful growers.  An example: the German cultivar 'Nugget' was known to carry a very heavy virus load of multiple types of virus without effect except when placed under extreme field stress; yet reported yields from growers were as high as 2400# dry/acre. "Cascade" hops were also evaluated in university trials with the presence of viruses having little to no effect on yields.

It is far more common to find during a full professional consult of growers'  under-performing hopyards that it is actually case of improper cultural practices. Lack of water and fertilizer at critical times, incorrect soil pH, soil compaction, and poor disease and weed controls are evident as the main contributing factors to poor hop vigor and yields. Often there is no adequate control of insects and weeds that are known vectors.  Hop growers should re-examine every aspect of their cultural programs before accepting the presence of virus as the sole explanation to their problems.
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GLH continually monitors hop vigor levels in all our produced hop transplants in our own trial yards. We replace propagation stock with cleaner plants in a regular rotation. The USDA is aware that the increased interest in growing more hop varieties for craft brewers has put more pressure on them to ramp up the budgets and programs that produce more treated mother hops that hop propagators use to create hopyard transplants. 
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​GLH is a MDARD licensed and inspected plant nursery. 
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​Further reading:

Detection and Elimination of Viruses in USDA Hop (Humulus lupulus) Germplasm Collection

Viruses and Viroids Infecting Hop: Significance, Epidemiology, and Management

Do's and Don'ts

One of the ways to increase hop's potential for winter damage is to cut bines too short during harvest. If you remove the energy-producing top growth completely prior to fall dormancy, the plant may not have adequate energy to initiate vigorous spring growth. A harvest cutting height of 2 to 3 feet is recommended for most hop varieties.  Ideally, allow 6-8 weeks of top growth to remain after harvest before removing remaining bines to ensure adequate storage of carbohydrates for winter.  A final fall cut bine height of 2 inches above visible crown buds is recommended.  Cover any visible crown buds with a shallow layer of soil for winter protection. Read our previous posts for more on minimizing crown damage.

Initial spring bine growth and emergence utilizes stored carbohydrates in the permanent fleshy root system. These stored carbohydrates are used for initial spring emergence and growth until the hop plant has reached about 6 feet of bine height. After this primary push, energy produced by photosynthesis and nutrients gathered by the new shallow feeder roots fuels more rapid growth up to the wire. N-P-K fertilizers applied in the early spring season plays a small role in primary spring emergence of the bines. Vigorous spring emergence is determined more by how well the plant stored energy the previous fall before going dormant.

Avoid late season post-harvest applications of nitrogen in excess of 80 to 100 pounds N/acre; this can delay proper dormancy and increase disease susceptibility. Plants that are late going into dormancy due to excess nutrients are much more likely to be damaged or killed by winter extremes.
In conclusion, fall applications of potassium are beneficial to ensure a great spring start and healthy future growth in your hopyard.

Japanese beetles are proving to be a formidable foe in hop yards located in the Great Lakes region.  The beetles can cause significant damage to hop foliage and bines in a very short period of time if left uncontrolled.  Two beetles can strip a large hop leaf in a single day and when their numbers reach the thousands, the beetles can strip a hop yard in just a few days.  Organic hop growers find controlling them especially frustrating because they cannot apply the synthetic chemical controls commonly utilized.

Here are some control strategy tips for all hop growers – organic and non-organic.

First concept: Beetles attract more beetles.

I do not consider Japanese beetles to be a threshold control-type pest where the decision to spray is based on tolerating a certain level of pests before treatment or spraying is done.  Female beetles excrete pheromones to attract males and mating is a gregarious affair – a “beetle orgy” for lack of a better term. Beetles fly into the wind and follow the beetle pheromone trail to the plants and leaves where feeding and mating occur. Females apparently leave pheromones on the leaves; as I note that beetles arrive and continue to congregate on the same leaves – even if the original beetles are removed. However, a good hard rainfall seems to wash away this residual pheromone trail.

It is well known that hanging pheromone traps can attract large number of both male and female beetle from great distances.  A population of mating beetles will grow exponentially as congregating beetles emit stronger pheromone trails for newcomers to follow to the orgy – just like a pheromone trap.  Allowing the beetles to establish a population in a hop yard is exactly like hanging pheromone traps in the middle of your hop yard.

Controls & Strategies:

Knockdown Chemical control.  Traditional spraying with chemicals such as bifenthrins or pyrethroids are all commonly used to control adult beetles on hops.  Organic growers have to be a bit more creative since this is not an option in their hop yards.  Spraying with products like Impede, Trilogy, or SurroundWP may be options for organic growers to consider. The insecticides containing bifenthrin, imidacloprid, or other pyrethriods are no longer my favored first control choice because I found using them caused a flare of increased populations of spider mites a few weeks later.

There are several other ways to reduce the damage caused by beetles.  Using some or all of these strategies can help keep populations of the beetles under control for all hop growers.

• Intercept beetles flying in on pheromone pathways with trap plants like grapes and Rose of Sharon.  There are several plant species the beetles like even more than hops.  The trap plants can be treated with systemic pesticides instead of the hop yard. (this is still not an option for organic-certified farms). Small hop yards can often collect beetles congregating on the trap plants into buckets with a little soapy water in them.  The idea is to keep the beetles from establishing a strong pheromone pathway to the hop yard.

• Make the plant unpalatable to feeding beetles.  Using products like diatomaceous earth or Kalolin clay (Surround WP**) irritates the mouth parts and body joints of the beetles.  Think of it as sprinkling very fine crushed glass powder into your salad and your favorite chair.  If you have ever worked with fiberglass insulation, you know the sensation of itching all over!

• Disguise the hop plant.  Beetles feed only on certain plants and hops happen to be one of them.  What if you changed the way a hop planted smelled or tasted to the beetles?  I noticed plants sprayed with phosphites seem to have less feeding activity.  Spraying hops with a plant extract/oil like citrus, peppermint, cinnamon or cinnamitc acid also reduced activity in the hopyard. My personal favorite is a citrus/boric acid pesticide called Prev-Am. I also notice that hop leaves sprayed with kalolin look whitish and apparently have a different look to the beetles. Many of the beetles just fly on by to the next upwind plant they recognize.

• Use milky spore on hopyard soils to combat the grub phase.  Know that the mated female beetles drop to the ground under the plant where they have fed to lay their eggs. The grubs feed on the hop roots.  Next year the beetles don’t have to fly in – they are already in the hop yard soil with a bigger potential population than the year before! Timing is critical for application of milky spore – small grubs are easier to infect than the large mature grubs that move deeper into soil later the season. Time milky spore applications for early August in mid-Michigan. Clean row cultivation/ tilling also results in lower populations of grubs surviving.

• Treat infested areas near your hop yard, if possible.  Often there are linden, basswood, river birch, wild grape or other feeding sites near your hop yard you are unaware of.  Take note of wind direction and days when fly-ins of Japanese beetles spikes.  With a bit of detective work these sources can be identified.  Sometimes treating under a neighbor’s linden trees with fall grub controls can have a big effect on the number of fly-ins to your hops. (a wee-bit neighborly, too!)
  
• Spray early morning or evening when the beetles are less apt to fly away. 

Combining all of these strategies can help control this damaging pest.

Foliar symptoms of chlorine toxicity include burnt leaf margins and spotting on mature leaves; yellowing and premature leaf drop.  Plants do not respire and convert carbon dioxide efficiently and protein synthesis is reduced.  The hop plant appears light green with thin weak leaves; even though there is ample nitrogen present. Hops set cones poorly and are also very light green.  The cones have lowered levels of organic acids and light aromatic compounds relative to variety averages.

Feeder roots and new shoots appear scorched.  Symptoms of toxicity increase during drought conditions; especially if a fertilizer containing high amounts potassium chloride is applied when there is little rainfall to leach away the excess chloride salts. Onset of symptoms can be very sudden – a stressor caused by heat or a missed irrigation.

A concern is when hopyards experience these stress symptoms (which are often diagnosed as a possible potassium deficiency) that the correct action is taken.  Muriate of potash (potassium chloride) is often applied to correct the symptoms without doing a soil test first to see what the existing chloride salts levels are.  This additional chloride can make the problem worse and ruin the alpha levels of the entire crop.

It is commonly recommended to do a pre-emptive soil test to determine nutrient / salt levels when the hop bines are climbing the twines. If chloride levels are high; then an alternate form of potassium fertilizer, such as sulfate of potash or potassium nitrate should be considered.

If overall potassium levels are low, and muriate of potash is used; it should be applied in the fall post-harvest season to allow the chlorides to leach out over the winter.  Also,  poultry or swine manure applications should be switched to cattle or horse manures. If poultry or swine manures are used; it is advised to apply them to alternate rows in alternate years.  Fall applications of manures that are tilled into the soil and allowed to fallow over the winter are the most effective.

In summary, if hop plants show poor color, vigor, fertilizer response, and symptoms similar to those pictured:

• Do a mid-season soil test and/or foliar sample to see what levels of chlorine and potassium are.  Don't just guess.
• If high levels of chloride salts are present leach them away from the root zone by irrigating heavily with clear water.  This is a “do-over” like erasing a chalkboard. New amounts of nutrients will have to be applied to replace what leached away with the excess salts.
• Consider switching to an alternate source of potassium such as potassium sulfate
• Switch to cattle manure instead of poultry manure
• Maintain a soil pH between 6.2 and 6.8 for most hop varieties to keep nutrients available and balanced
• If the hop cone alphas are low, resin &oils high, aromas low; double check soil tests again.  Look for out of balance cations (calcium) and anions (chloride). Adjust the nutrient program a necessary.

Great Lakes Hops   January 6, 2014  reprints by permission.

Pyganic insecticide is a very short-lived contact insecticide that is approved for organic use and is OMRI certified.

It contains natural pyrethrins derived from chrysanthemum plants and can be sprayed right up to the day of harvest. PyGanic is very useful for quick knock-down of pests such as Japanese beetle adults, mites, aphids, and leafhoppers.

It breaks down very quickly when exposed to sunlight.  Avoid spraying when bees / pollenators are actively foraging.

Hops are not specifically listed on the label. However -"may be used on most crops because its active ingredient is exempt from tolerances when applied to growing crops". Hops fall under the category of Outdoor Grown Crops.

Note that PyGanic is a non-selective insectide and will kill beneficials and predator insects as well as the target pest.

I would recommended to  reserve its use for knockdown when pest levels go out of control.  As with all pesticides; read the label carefully before use.