A shared guide to the do’s and don’ts of growing hops
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No doubt about it, for many new growers hops are a difficult crop to grow well. Fast growing hop plants require lots of balanced nutrients and water with critical timing of applications; making hops a real challenge to keep up with when compared to most other crops. Getting the hops to climb to the top trellis wire and produce fully developed side arms with lots of cones seems to be an unattainable goal sometimes. There always seems to be a guy named Murphy lurking around, ready to throw a wrench in the works; despite a hop grower’s best efforts. Wind, rain, drought, and pestilence... yet there are lots of pretty pictures of hopyards and recorded harvest yields to show it is more than a dream.
It is common to find in many instances, less experienced hop growers do not fully understand many integrated hopyard management practices and how plant nutrient availability and growth is affected. This following discussion covers a few of the issues that have been identified as potentially holding back hop growth and yields. These issues are gleaned from talking to, and working with hundreds of new hop growers and the challenges they have experienced.
These observations and field notes are intended to educate and provoke deeper, more in-depth discussions amongst hop growers and grower groups.
It's All About Balance
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.
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.
Viruses and viroids in hops is a hot topic nowadays since the advent of simplified virus tests. However, if a grower is experiencing vigor problems in the hopyard and the majority of plants are not reaching the trellis wire, forming full length sidearms, or generally yielding poorly; then other cultural factors such as soil pH, water, fertility, soil compaction, pathogen and weed controls are by far the most common causal factors and need to be re-examined and corrected FIRST.
Plant pathogens (this includes hop viruses and viroids) naturally accumulate in plants as they age and in cultivated hop yards the maximum crop yield potential naturally falls as time passes over a period seasons. Many people simply rationalize this as the plants are “getting old”. Plant viruses and viroids number in the thousands and coexist naturally in our surrounding environment. These viruses transfer from plant to plant, or even between plant species by a number of different vectors (insects, mechanical, root contact, etc.) . Plants that carry viruses and viroids often do not express symptoms unless the plants are stressed or weakened.
In nature, these pathogens are controlled and mitigated by plant vigor (healthy plants can carry a virus load with little external effects); annual cold and heat cycles that eliminates or sets back virus loads, or elimination of virus by new plant regeneration via seed. Viruses and viroids are considered obligate pathogens because they coexist with and rarely kill their host. Some viruses are actually beneficial.
Virus accumulation is an important consideration in long-lived perennial crops like hops. Single favored female hop cultivars are repeatedly cloned for years (sometimes decades) from the original mother lineage. This monoculturing totally bypasses the way viruses and viroids are are naturally controlled. Hop planting stock that is derived from older cultivars and hopyards often carry higher virus loads than planting stock that is derived from newer hop stock and cultivars that have been treated for virus reduction. The USDA is aware of these facts and has a congressional mandate to create clean seed and planting stock for ALL commercially important crops in order to remain competitive with the rest of the world. A single small USDA lab in the Pacific Northwest is the sole source for clean hop stock that has been heat-treated and cultured to remove viruses that are considered harmful. (see http://nationalcleanplantnetwork.org/HOPS_CPN/ for details.) Only a limited number of commercial hop cultivars are treated due to budgetary constraints. Many less popular hop cultivars do not ever qualify to go through this program for virus treatment. The hop cultivars that do get treated are available in only very limited quantities; sometimes as only few dozen plants or unrooted cuttings for growers and propagators nationwide. This is the only current government-funded source in the USA that creates cleaned hop stock. There are currently no other certified sources or certifying agencies for hops in the USA.
Great Lakes Hops (GLH) actively obtains, maintains, and propagates the cleanest newest nuclear hop mother stock available (emphasis on AVAILABLE) to us from this government program.
However, that being said - read carefully and understand the following.
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.
This is important to consider, because Downy mildew is prevalent everywhere and can destroy your entire hop crop if not managed and controlled. Grape growers face a similar situation and have developed very effective control strategies. Hop growers will need to do the same.
Many hop growers do not understand the importance of controlling downy mildew in their hop yard after harvest is completed. The fungus and the infection are not as visible because there are no new shoots or infected spikes to be seen. Many growers consider the season as finished and leave the yard unattended going into winter. IMHO this is a fundamental mistake in controlling Downy mildew in hopyards. Downy mildew is active whenever conditions permit – it simply doesn't care if it is springtime, summer, or fall. (The 2014 growing season attests to that.) Post-harvest fungicide applications and controls can be the most effective way to manage downy mildew in yards that have had the disease present and reduce the severity of downy mildew spikes during the following spring growing season.
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 spore type called a zoospore. This spore acts much more like a living microscopic worm than a fungal plant-like spore. The zoospore form helps downy mildew complete its annual life cycle by finding a safe resting place for it to overwinter or by forming protective oospores; where it will be protected from the harsh winter that is ahead. This is a high-risk period for the downy mildew organism – it is outside its host and can be attacked most easily at this point.
Hops are a very chlorine-sensitive crop. Hops varieties such as Cascade, Sorachi Ace, Sterling, Horizon, H. neomexicana and many other aroma hops commonly exhibit chlorine toxicity symptoms in many American soil types if fertilized improperly. Many other varieties of hops may not show clear toxicity symptoms but are held back and produce less than an optimal crop.
The element chlorine is common in nature and exists as an anion (Cl- ). It carries a negative particle charge and competes with other anions such as sulphates and magnesium if it is out of proportion to the other elements. It leaches from soils at about the same rate as nitrates. Excess levels of chlorides reduce soil microbe populations and reduce nitrogen conversion rates. Inputs to soils of chlorine are from natural rainfall, irrigation water, and fertilizers (potassium chloride). Swine and poultry manures have relatively high levels of chlorides compared to cattle manures. Chlorine is commonly found at ambient levels of around 50 mg/l in many soils (California excluded). Many formulations of chemical based NPK fertilizers have very high levels of chlorides. (Potassium chloride is a common source.)
Chlorine is considered a micronutrient and helps regulate the osmotic absorption of other nutrients that plants require. It often accumulates in foliar tissues at levels of 2-20 mg/l-1 of dry matter; even though plants require 10 to 100 times less to grow properly. Thus, deficiency symptoms are rare. A level of 180 mg/l in lighter-type soils is considered the upper range for hops production.
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.
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 chemicals commonly utilized.
Here are some control strategies 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 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.
Lynn, the head hop grower at Great Lakes Hops has over 30 years of experience in the horticultural field. Browse the blog articles here to find useful growing information for humulus lupulus, based on personal experience and observations at Great Lakes Hops.