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.
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.
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 visual toxicity symptoms but are held back and produce less yield.
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 sulfates and magnesium if it is out of balance to the other elements. It leaches from soils at about the same rate as nitrates. Excess levels of toxic 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 where hops are normally commercially grown. Many cheaper granular formulations of chemical based NPK fertilizers have very high levels of chlorides. (Potassium chloride is a common source.)
Chlorine is also 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.
Grower notes: Seeing heat-stress symptoms in some hop yards.
The older lower leaves yellow and fall off without any obvious signs of pests or disease. This is more common in years with a wet spring followed by a hot & dry June/July. The side arms are short but usually loaded with burrs in reaction to the stress. The hop plant is attempting to "re-balance" its transpiration losses through the foliage versus what the root system can supply. (The wet spring reduced the root mass.) To help the plants adjust and keep cone development on track, apply a top dressing of a guano or organic manure (we use Naturesafe Stressguard for this) and keep adequate water supplied. (and pray for rain:) )
Hops - Bottom Leaves Turning Yellow
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A male hop plant. Very rare in the wild. Stressed females can show signs of male anatomy but will be sterile and will not self pollinate. If you locate a male plant that shows no signs of female anatomy, you should eliminate it immediately as it will pollinate all the female plants in the area.
Most feral male plants are unknown type because they do not produce cones that can be tested. Hop breeders will use USDA registered males with a known pedigree (like increased resistance to mildews) to breed new varieties. Some triploid hops like Zeus and Columbus have an odd 3 sets of chromosomes (usually 2 male/1 female) which can revert temporarily to male flower production if severely stressed. The male pictured here is USDA19058M (boys are assigned numbers, while the girls get names). It is a registered high-alpha type male.
I am busy doing field checks with hop growers during the month of May. I am finding winter crown desiccation in new hop yards that did not have reliable snow cover. The crowns appear to have been exposed to sun & wind while the ground was frozen. The fleshy roots remain white - no rot is present. The frozen soil/roots could not supply water to the exposed crown as it is dried out by the sun & wind. There have been no reports of this type of winter damage from up North, where they had good snow cover. Varieties like Zeus, Glacier, Saazer, Nugget & Cascade were affected more than varieties like Chinook. Protecting these crown buds from exposure is important ! Some of these damaged crowns may regenerate slowly; given time.Click to enlarge
Our winter exposures and duration are longer and harsher in the Midwest than those out in Oregon and Washington.
Crown buds can be protected in several ways as you prepare you hop yard for winter. First, leave the hop bines cut at 24 to 36 inches high over the winter. The old bines supply extra sugars to the crowns and act like little snow fences; slowing the wind, holding snow and field debris around the crowns. Second, physically cover the young crowns - protective mulches or field soil 1 to two inches deep is a typical field practice. Third, apply a high potassium fertilizer in the fall to winterize the hop plants. Hop yards with low potassium levels experience higher levels of winter crown bud damage. A close placement of granular or dissolved through the drip system is necessary for it to be effective; since the fine feeder root mat formed during the growing season is breaking down and disappearing. The potassium ion prevents ice crystals from forming in the plant tissues and allows water movement at lower temperature ranges. (Think of potassium as anti-freeze for your hops!)
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The first largest bines to emerge on 2nd year or older hop crowns are not necessarily the best to train. These "bull" shoots have a large hollow core, like a straw; and easily kink or are damaged by late spring storms. Most crowns put out two to three of these, at the most; and crews can be trained to identify them and prune them out as they twirl climbing bines. "Bull" shoots are often a light olive green color with stretched internodes - some field practice clipping a few will reveal which have the hollow stems.
Experienced hop growers will be the first to tell you that a regular weekly schedule of checking your hopyard for problems can save big headaches, time, and cold hard cash. Being a good grower isn't about who has the biggest pesticide budget! Catching problems like pest and fungal outbreaks early is critical to controlling them successfully; with minimal treatments - before the damage is done. Proper scouting includes a close examination of the entire hopyard's environment (including the surrounding fenceline perimeter's).
(This pest is capable of defoliating entire plants in less than a week)
For quick knockdown of a Japanese beetle /Potato leafhopper outbreak for growers with RUP certification - check out Brigade 2ec or Leverage 360/2.7. Both are labelled for hops.
TO DO LIST
If this sounds like too much work; please do consider hiring a professional crop scout. They know what to look for and when to look for it. Their services are relatively inexpensive and their advice - priceless.
Properly done scouting and recording what you see in detail lets you identify patterns and conditions that affect the hop's growth and what conditions trigger disease and pest outbreaks. I recommend making a check-off form you use weekly during the growing season that covers all the above items so you don't miss anything. This will not only make you a better grower- it will make you a PROACTIVE grower. (I like to call them Jedi-growers because they always seem to know what is going to happen before it does.) Proactive growers can make minimal, targeted sprays; anticipating disease and pest cycles. They consistantly adjust - fertilizer, irrigation schedules, cultivation; like a steady clock. They also always seem relatively cheerful and un-stressed. (nice side-effect that both wives and partners seem to appreciate!)
Scouting is something I do habitually 24/7 - I'm looking when I'm watering - I'm looking when I'm weeding- Heck, I'm looking when I walk the dog!
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.