Beneficial Post-harvest practices in the Hopyard

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.

11.)    Do not compost or put harvested bines back into the yard if pathogens were prevalent. Do not spread other hopyards' waste back into your hopyard if you are a processor who handles other grower’s hops.  Properly composted harvest waste must reach a temperature of 130 degree F. to kill pathogens and few growers can accomplish this successfully and instead end up with piles of decayed plant material that continues to be a source of pathogens.

22.)    Change your irrigation frequency post-harvest.  DM motile zoospores require wet saturated soil to persist and move in the soil.  The quickest way to encourage fall DM crown and bud infection is to leave the irrigation controller running daily going into the fall season.  After harvest run the hopyard irrigation on the dry side and only irrigate a couple of times a week; if at all. In most areas, rainfall coupled with cooler temperatures is adequate.

33.)    Limit your fall applications of Nitrogen to 80 pounds per acre or less.(banded) Fall fertilization is about replacing some of the nutrients removed by the hops during the growing season and rebuilding the soil microbe population that the high usage rate of synthetic fertilizers destroy. However, high rates of nitrogen applied to fall hopyards can delay natural dormancy and enhance proliferation of pathogens like downy mildew.  Many grower use organic light manure applications both spring and fall to rebuild the soil. Additional fall applications of potassium, lime, or gypsum has been shown to be beneficial to increasing next season hops vigor.  Weak nutrient-deficient plants are more susceptible to winterkill, diseases and pests.

44.)    Apply fertilizers and manures alongside the rows; NEVER on top of the crowns.  High levels of excess nitrogen near the hop crown coupled with wet soil create an ideal condition for DM and crown rots to proliferate.

55.)    Till the hopyard soil. Simple mechanical soil cultivation each fall improves soil aeration and reduces the wet compacted soil conditions that mildews and pests like nematodes favor. Many spores and nematodes are destroyed by this simple fall practice.  

66.)    Apply systemic fungicides to the hopyard post-harvest.  The idea is to limit fall spore production in infected plant bines and leaves and destroy  pathogens that will overwinter in the hopyard. Systemic applications containing  phosphonic acids will move downward in both the plant and soil; providing protection against  motile zoospores. Tanos or Pristine, combined with Phostrol / Aliette make an effective application for yards that have experienced downy mildew. Usage rates are lower than during the growing season.

77.)    If your hopyard experienced heavy pest and disease pressure during the season, consider a late fall dormant oil spray. Horticultural oils  applications will reduce overwintering insects and mites / their eggs and  many types of fungal spores.

88.)    Trim bines of infected varieties short in late fall after leaf drop and remove the debris from the yard. Wait 4 to 6 weeks after harvest to cut the bines short to allow the carbohydrates in the remaining bines to translocate down into the crowns and help build strong budding at the soil level. The optimum height to cut is about two inches above the new crown buds.  Cutting closer into the crown at this time creates a large open wounds that allows easy access for many types of crown rots. Be sure to cover any  visible crown buds with soil or light mulch before the winter sets in.

99.)    Avoid over-application of heavy wet mulches over the crowns. Covering exposed crown buds with field soil to prevent winterkill of buds is probably a better choice in most larger hopyards.

110.)  Get control of those weeds! Hopyards with lots of weeds have higher levels of mildew infections. Use herbicides like Volunteer for grasses and a contact burn-down like Aim for broadleaf weeds. Organic growers need to cultivate more frequently and can treat weeds with natural products like clove oil. Always destroy weeds before they set seed!

111.)   Remove black plastic or ground fabric used for weed control. Controversial, we know, but . . .  Plastic mulches hold excess continuous moisture and heat under the cover and result in higher levels of disease and root rots.  It is difficult to rebuild the nutrient and microbe depleted soil around the plant and remove underground rhizomes with a permanent plastic mulch or row cover in place. The tradeoff of fewer weeds by using poly row covers in exchange for for lower yields and higher disease levels is not logical in our humble opinion after working with hundreds of hopyards and comparing grower results.

112.)   Dig up your hops!  It is a great idea to dig up a few plants in the yard each fall to inspect the roots and crowns. Are the roots white and healthy in appearance? Any stunting, decay, or lesions?  What is the level of soil compaction? This is a great way to find early signs of many pathogens such as crown rots and nematodes. Then simply replant the crowns when you finish these spot checks. J

Blogged by hop grower Lynn Kemme / Great Lakes Hops-  Fall 2015 

Hop pesticide review – Horticultural mineral oils- Cheap but effective in the hopyard.

Refined horticultural mineral oils go by many names - - dormant oil, summer oil, paraffinic oil, crop oil, stylet oil, white oil, etc.   All oils can be sprayed alone or with other compatible pesticides and have a direct contact mode of action on labelled pests and fungi. Oils direct contact action means very little possible resistance issues compared to many other pesticides. They are an inexpensive, safe, effective, and easy-to-use control for a quick knockdown of pests and pathogens like spidermites and mildew. Applied as a fall dormant spray it eliminates possible overwintering insect and mite eggs and fungal spores and mycelium. (Great as a post-harvest treatment going into late fall.) Crop oils also enhance weed control when combined with several different broadleaf and grass herbicides.  These oils are commonly used in field crops, orchards, and vineyards and should be in every hopyards arsenal of controls. They are considered to be a relatively soft control on beneficial insect populations, but should not be applied during beneficial insects active hours – Example: during bees foraging hours.

Horticultural oils to have a couple of important features that are necessary to understand before purchasing or applying them.  Mineral crop oils are refined with different weights; from very light and thin viscosities to heavier oilier types -  very similar to different grades of automotive oils.  They have the majority of sulfates removed to reduce crop burn potentials; but all have the ability to severely damage hops if used incorrectly.  The general rule of thumb is to select a thinner grade oil the hotter the day temperature is. (light summer oils vs. heavier Avoid application to the cone-bearing portions portion of hop plants and bines; as the oil will damage burrs and turn contacted cones brown. It is recommended to treat the lower non-coning portions of the hops near the ground to control populations of mites and mildews that tend to spread upward as the season progresses.

dormant oils).  Spraying these crop oils should be done during the coolest part of the day or evenings. Morning spraying should be avoided if hot mid-day temperatures are expected to climb above 80 degrees. 

Some manufacturers have obtained both labelling for hops and organic production.  Check the use labels carefully of different oils carefully to determine the proper grade and particulars of each product.

Some manufactures’ of horticultural crop oils are JMS Corporation, the Drexel Chemical Co., and Helena Chemical Corporation.

Blogged by hop grower Lynn Kemme / Great Lakes Hops    Fall 2015