Not a punctuation error in the title of this blog post. All hop growers transition from “is it time…” to “yes it’s time” and then “WOW… is it time!” for hop harvest. This year was difficult for hop growers on the east side of Nebraska and relatively typical for those in the middle to western areas of Nebraska. There are many topics covered in this blog post but all are timely at this point.

Timely Topics

• Statewide Progress
• Importance of Harvest Timing
• Determining Cone Maturity
• Analytical Testing
• Drying Hops
• Pelleting
• Storing Hops
• Upcoming Events

Statewide Progress

A late spring warm up this year in eastern NE delayed hop emergence and excessive rainfall events occurred during soft new regrowth. If preventative fungicide applications were not timely, significant downy mildew infections damaged susceptible and tolerant varieties. For the most susceptible varieties, this led to total top death and regrowth that was significantly delayed or systemically infected. Growers are seeing significant reductions to those expected, some not being productive at all and directly reflective of variety vigor and disease susceptibility.

Central and western NE growers did experience a later than usual warm up in the spring but plant growth was able to generally catch up to that expected in the region. Hop cone development is on target but cone weight per plant appears slightly less than that seen in 2017 and 2018.

Importance of Harvest Timing

Brewing properties include bittering compounds found within the resins, essential oils, and the polyphenol substances or tannins.  These qualities are influenced by hop varietal character, ecological and environmental conditions, and cultivation practices implemented. There are multiple acids found within resin compounds, however, cohumulone is the principle compound associated with α-acids and colupulone is that associated with β-acids.  Hop cone lab analytical testing will generally measure total α-acids and β-acids but additionally provide measurements specific to cohumulone being a percentage of total α- acids and colupulone as a percentage of total β-acids.  This information is important to brewers who will use this product in their brewing recipe. 

During cone maturation, the β-acids are first produced and then these gradually transform to α-acids through exposure by solar radiation.  Resins within the cone will initially be high in β-acid and low in α-acid content but this will shift during the ripening process.  Cones that are exposed to bright light or are over-ripe, will have very high α-acid content in relation to β-acids. It is important that light irradiance be as balanced as possible in the plant canopy so that cones will have consistent quality throughout. 

Essential oils in hop cones contain more than two hundred different volatile compounds that create the individualized aromatic qualities noted in hop varieties. The essential oil compounds are grouped either as hydrocarbon fractions (terpenes) or oxygen fractions (oxidated).  These volatile substances are similarly formed from acetic acids found within the oils and influence α- and β-acid oxidization during cone maturation, post-harvest processing, and storage.  This degradation process reduces the qualities associated with the economical value of hop cones.  Cone harvest should commence when attributes are optimal and handled efficiently during processing, packaging, and storage to maintain characteristic qualities until used. The challenge the grower has is to all maximum hop cone maturation for α- and β-acid content but not delay so much as that the aromatic qualities have changed or degraded.

Determination of Cone Harvest

Harvest date differs by hop cultivar and also is influenced by the location, specific care, and environmental conditions. Qualities of interest for the brewing industry are the alpha-acid content, related to bittering ability, and essential oils, which includes more than 300 complex compounds, creating the unique fruity, spicy, nutty, or floral aroma characteristics. Also of importance to brewers is beta-acid content.  These acids contribute slightly to beer bittering but are most important in bringing antiseptic qualities into the beer and improving shelf life of the final product. Hop cones should be harvested when these three components are at their optimal stage.  Too early of harvest, the acid content may be too low, and with too late of harvest, the aroma will have faded and cone storage life is shortened.

A simple test to check on maturity of the hop cones is feel and smell. A cone that is not ripe will be soft and light, feel slightly damp, and will remain compressed when lightly squeezed. Pull back a bract leaf of the cone and look for yellow lupulin.  Ripe cones will have large oily lupulin crystals present, whereas immature cones will have a light dusting. Cones ready for harvest will feel dry, spring back to shape when squeezed, and have their distinct cultivar hop aroma.

Commercial hop growers determine optimal harvest time when cone moisture content reaches an average of 23% dry matter. This stage of maturity is typically considered to hit a balance between the three important characteristics of hops for brewing. To test for dry matter content of hops, do the following procedure;

1. Collect a total of 100 – 125 cones from a random sampling of plants in the hop yard
2. Weigh an empty container in grams (tare weight)
3. Put collected cones in the container and get the wet weight
4. Dry the hops for 8-10 hours in a food dehydrator or convection oven at 135^oF, this will bring the moisture content down to 0%
5. Weigh the dried hops in the original container with the known tare weight
6. To calculate percent dry matter, complete the following formula:

(Dry cone weight ÷ Wet cone weight) x 100 = % Dry Matter Observationally, hop cones nearing maturity will become light green, with a dry papery feel, and the lupulin coloring will turn from light yellow to a dark yellow-orange within the bract leaves.

Analytical Testing

To determine optimal hop harvest window, commercial growers may send samples into a laboratory for analysis of the hop cone profile.  This comes at a cost, but worth the investment if you are a serious grower selling hops to commercial brewers. Analytical testing is especially important post-harvest so the grower can provide information to buyers regarding the crop.

There are different types of tests that can be completed by labs. For harvest timing, a grower is interested in quantifying alpha and beta acids, Cohumulone, Colupulone, and dry matter. The results from the tests can be compared to that found in literature for the specific cultivar being grown, as well as, to historical records maintained by the grower. Post-harvest analysis would additionally include testing of the hop storage index and total essential oil content.  Some laboratories are able to identify hop essential oil profile which is at a much higher cost. The profile will quantitatively identify content of some of the key chemical compounds that make up the essential oil complex, allowing comparison to hops grown in other areas.

Drying

Picked cones have roughly 76% moisture content and need to begin the drying operation immediately. Small growers will generally build their own drying unit, comprised of a wooden framed tray with a wire hail screen bottom, and, a fan that blows air upward through the tray. Hop cones are placed evenly within the drying tray, approximately 6” deep. The fan must have baffles to direct all air being moved, upward and with even distribution through the tray of hop cones.

Ambient air can be used given summer conditions are typically warm and dry, however, drying times vary greatly. Using a controlled heating air source will speed the process. Target temperature during the drying process is 130 – 135^oF and should never exceed 140^oF as cones will discolor and qualities will be reduced. The goal is to reduce cone moisture content to 8-10%. Drying can be completed within a day using unconditioned air, but with temperature controlled dryers, cones can be dried in 8 – 12 hours. Following drying, the cones are cooled using unheated air and allowed to rest for 1-2 hours (conditioning) to allow tissue moisture to balance within the cone prior to the packing process.

Pelleting Hops

Pelleted hops are generally used in commercial brewing operations. Whole cones are milled in a hammer mill, breaking them down into small uniformly sized pieces with a minimal amount of dust. The milled product then goes into a pellet machine that creates the pellets.  Pelleting occurs by  pressure being exerted on the millings through a die, which is a metal plate having a “honeycomb” of holes drilled through it. The pressure compresses the millings and extrudes the resulting pellet.

Pellet manufacturing is a precision process requiring care in doing so. High quality pellets will be firmly pressed and uniformly green. If the process is done too quickly, heat will be generated and cause a yellowing or brown burning on the hops. Hop buyers will carefully scrutinize pelleted hops, concerned with pellet structure and consistency, color, aroma, packaging and hop analysis.

Storing Hops

Hop cones will deteriorate over time, reducing aroma and their bittering ability. Stale hops will take on a cheesy or “skunky” flavor and ruin the brewed product. Cone quality of hop is affected by heat, light, and the presence of oxygen. Heat causes chemical breakdown, greatly affecting aroma characteristics and diminishing bittering capabilities. Exposure to sunlight following picking accelerates chemical breakdown and, in time, creates off-flavors in the brewed beer. Presence of oxygen allows for the chemical compounds to oxidize, causing an old, cheesy aroma. Packaging in plastic bags is not advisable since they are not actually airtight.

Multi-layer Mylar foil bags provide the best packaging for hops. Hops cones or pellets are vacuum-sealed in the package, blocking light and preventing oxygen from degrading the quality of the hop cones. Hops can additionally be nitrogen flushed prior to sealing to eliminate any oxygen from being in the package, providing a longer storage period.

After packaging, hops should be stored in a cool location (below 68^oF). Each hop cultivar differs in how long it can be stored before its quality degrades.  Aromatic hop oils are the most vulnerable to breaking down, followed by the alpha acid content. If the hops grown are to be used for a burst of aroma added at the end of a boil, then it should be used immediately upon harvest.  Otherwise, if properly packaged and held in optimal temperature storages, hops can be stored for several years.

Upcoming Events

Mark you calendars for the first annual Capital City Oktoberfest at Gateway Mall on September 7th and 8th. The Nebraska Hop Growers Association will have a booth providing grower contact information and hop resources. Others you’ll find are the Lincoln Lagers Homebrew Club, Great Plains Culinary Institute and the Nebraska Craft Brewers Guild. Each has something special at their booths so make sure to stop by! You can get tickets at https://www.capitalcityoktoberfest.com/tickets/?fbclid=IwAR0JFIsm5Uk8QV1x-WMitVANNMY2-kKRbXu7xj54ujdHR6gg74sE8yIj_r8.

Timely Topics for Nebraska Hops

• Growth Progress
• Nutrition and Irrigation
• Burn-off of lower growth
• Insects
• Disease

Growth Progress

The variety trials located at UNL east campus in Lincoln, NE represents eight popular commercial hop cultivars being grown on a traditional 18′ trellis system. This has been a challenging year for agriculture in general and also for hop growers. The late spring warm up and ongoing rains resulting in slowed growth following timed cutback and made plants vulnerable to disease pressure from cool temperatures and plenty of free moisture. This year it was critical to have preventative fungicide applications in place to protect vulnerable cultivars, especially for downy mildew.

The variety trials include; Columbia, Centennial, Chinook, Cluster, Crystal, Perle, Willamette, and Zeus (CTZ). All cultivars made it to the top wire by July 8th with the exception of Willamette, Perle, and Columbus, in which their average height was 1/2 to 2/3 height. This is expected for Perle as it is a less vigorous cultivar, however, for Willamette and Columbus, delayed spring warm up delayed plant regrowth. Early flower development was evident for Zeus, Cluster, Willamette, and Centennial, full flowers for Chinook, and no flowers were evident for Columbia and Perle.

Nutrition and Irrigation

Approximately 70% of the nitrogen needed by hops has been accumulated by the plant to this point. It is important to monitor plant nutritional health and note indications of color variation, yellowing, and leaf drop. Large growers should have a leaf petiole analysis done to accurately determine nutritional health, however, most smaller growers will approximate plant health through interpretation of needs from the soil lab test results and making repeated plant growth observations. A majority of NE hop growers soil conditions will have adequate nutrient elements for hop with N being the primary element needing to supplement to maximize plant growth. Elements of greatest importance include nitrogen, potassium, and calcium. Magnesium and sulfur can potentially be limiting factors in some soils.

Hop plants are undergoing transition from vegetative stage to flowering, followed by cone development. As rain events are irregular, it is critical to initiate consistent irrigation on a daily basis. Drip irrigation is optimal as overhead irrigation can induce disease pressure. Hop typically needs from 27 – 32″ of moisture during its growth period, this is roughly from April through September. Irrigation needs will vary by individual soil conditions but is greatest during July and August when rains are irregular and the plants at their most critical period of development. Many growers will benefit from irrigating daily and with a combined total of 1 1/2″ – 2″ of moisture weekly.

Burn-off of Lower Foliage

The emphasis for one and two year old hops is development of the underground wood for future productivity. This is done by maximizing above ground foliage to manufacture carbohydrate reserves needed for plant growth. Plants more than three years old should be managed for productivity and health. General recommendations suggest removing the bottom 36″ of foliage from the bines and plant growth remaining untrained on the ground. This will improve on air movement within the plant canopy and reduce potential for disease infections. Burning back additionally reduces nutrient and irrigation needs of the plant by focusing these to the developing cones.

Age of plant and height of plant should be taken into consideration when initiating leaf stripping and to what extent (height) it is done in order to reduce impact on yield and resin content within the cones and carbohydrate reserves in roots. Burn back is typically done chemically using products such as pelargonic acid or carfentrazone (follow labeled instructions for leaf stripping of hops).

Insects

Insect pressure to monitor for include leaf hopper and spider mites. There is limited data regarding management of leaf hopper in hops as these insects feed on a wide range of host plants. There has been indication that some varieties of hops tend to be favored by hoppers and include Liberty, Fuggle, Mt. Hood, Tettanger, Santium, and Newport. Hopper pressure is encouraged by mowing of the drive rows and less insects were observed when these areas were planted with cover crops, such as, red clover. Natural predators include; damsel bugs, lacewings, lady beetles, parasitic wasps, and spiders. If pressure is high, it is best to control with targeted pesticides and not using broad-spectrum pesticides. Growers have found control using pesticides containing azadirachtin or pyrethrins.

Hot and dry conditions may result in increased spidermite pressure. Monitor mite numbers through scouting and note presence of potential beneficial insects, such as Stethorus sp. and predatory mites. If mite pressure is high, webbing will be noted between the leaf margins and pin sized yellow dots that lead to generalized “bronzing” of the foliage. In severe infestations, leaf drop may occur. The most damaging period for mites is on the developing cone which can reduce alpha-acids in the cone and affect the visual quality of the flower bracts. Most growers treat when mite levels are between 5-10 mites per inspected leaf. Mite populations can build quickly in hot conditions so monitor often during July and August.

Japanese beetles made their appearance in Lincoln on July 8th and damage was evident by July 12. Adult Japanese beetles aggregate and feed and mate in large groups following emergence from the soil. There are no established threshold levels and this insect can be frustrating to manage. There are indications that some hop varieties are not as favored by Japanese beetles, such as Chinook and Cascade, whereas Hallertau and Northern Brewer tends to be most favored. Pyrethroid insecticides are the best line of control and can provide 7 – 10 days of control. Neem-based products, such as azadirachtin can give 1 or 2 days of residual activity and has good contact toxicity if there are many beetles present in the hop yard. To reduce the negative effects of over application of pesticides, spot treating heavily infested areas is the best control strategy.

Diseases

Plants that tolerate downy mildew or new stems were trained to replace infected bines will have likely outgrown early infection however may exhibit delay or tip infection symptoms. Warm night temperatures should suppress any additional development of this fungus. Lower leaves should be stripped if possible, however consideration of the extent of this should be determined by the condition of the plant and its ability to be regenerate energy into the underground plant portions for the next year.

Fusarium canker may cause bine wilt with mature hops. This is observed as sudden death of the entire plant, even though it successfully grew to the top wire and may be flowering. Fusarium spores are naturally occurring in soils and not typically a problem unless the conditions are present for infection. This occurs with excessively wet conditions and stem injury sites, such as from stem movement at the soil line. Hilling of soil around the base of bines promotes growth of healthy, adventitious roots and will reduce the potential for bine wilt.

Timely Topics for Nebraska’s Hop Enthusiast

• Reports from across NE
• Weather and growth concerns
• Summer cultivation strategies for optimal harvests
• Insects in the hop yard
• UNL Hop breeding update

Reports from across NE

Eastern NE- Hop growers near the Missouri river continue to deal with flooding in several of their fields. Extensive rains have encouraged weed growth and slowed progress in training. Focus has been given to fields that optimize time and labor to maximize harvest potential with this worst-case scenario. Make sure to lend a hand to these growers if you can!

Northern NE- Hop growth near Norfolk has been good and appears that the flooding observed this spring did not greatly affected the crop as long as the fields were not in direct path of moving water. Temperatures have been normal with rainfall near normal in May but 3″ behind for June.

South central NE- Conditions early season were optimal for hop growth however wetter than usual conditions in May has caused much disease pressure. Growers that used a preventative spray program or have resistant plants are having good growth but slightly slowed as temperatures have been steadily comfortable for humans but not for pushing hops.

NE Panhandle- according to the NCDC (National Climatic Data Center), May was a mixed bag of 24 rain events and 4 events of light snow, oh, and 15 days of fog. This all occurred after we cut back the hops at PHREC the end of April. Somehow, Scottsbluff still had about 12 “fair” days with sun. The plants appeared to be on target and then 0n May 26th a storm broke most of the trained hops growth off. Plants had to be retrained, delaying their growth in this region.

Weather and growth concerns

It seems that we’ve had continual bouts of rain in the east and cooler temperatures than usual across the state, increasing the incidence of disease in the hop yard. When investigating historical trends to justify my thoughts, I found out that the weather events we’ve had, still fall within the normal range overall, however, was wetter than usual in May and a bit on the dry side in March and June. Normal rainfall in Lincoln, NE area is about 4.29″ in May and 4.33″ in June and we observed 7.29″ in May and 2.5″ so far in June. If you consider that hop cutback was made in late April, the newly emerging growth in mid-May that we intended to train was soft and low to the disease pathogens remaining on the soil or previous vegetation. A fungicidal spray program should have been implemented just as soon as the new growth became visible. Many of us waited too long and now disease pressure is high.

I tend to be conservative in chemical applications when ever I grow crops, others are very regimental in preventative chemical treatments. It is important that individual growers develop a pest control strategy using multiple information resources. This begins with knowing the disease/pest vulnerabilities of hop varieties grown, the conditions typical of the hop yard, historical climatic data, and information gathered through networking with other growers in the area.

Some of the work we are doing in our across the state hop trials includes taking observations about insect and disease pressures and the plants ability to resist, tolerate, or succumb to them. You’ll find throughout the season I’ll comment about our findings through this blog as an opportunity to learn from our challenges.

Summer cultivation strategies for optimal harvests

It is important to implement a fungicidal treatment program and manage weeds in the hop yard. Consider burning off the lower 24-36″ of the foliage on the bine as the plants reach their final height and move into the reproductive flowering stage. The vegetation burn off will improve on air movement within the canopy, as well as, greatly reduce the spread of fungal spores upward in the plant canopy.

Use care in nutrition management, adjusting N application rates according to expected cone productivity. With the late plant development observed this year, N needs by the plant will be less than previous years. Providing N at levels higher than needed will result in increased vegetative growth, fewer cones, and increased potential for “Angel Wings” on the cones.

Insects in the Hop Yard

Scouting of the hop yard should monitor insect pressures and determine what immediate and potential controls necessary. Care should be given to use pesticides that target the specific insect to be treated and limiting the use of broad spectrum pesticides. The young leaf hopper population is building quite rapidly with the warm and moist conditions present. Given hop plants are not growing as rapidly given the cooler spring and the possible disease pressure, it is recommended to consider implementing a treatment plan to keep hopper populations down. There are thrips and spider mites present but it appears as if populations are being well managed by natural predators.

UNL Hop Breeding Update

Dr. Keenan Amundsen and his research team at UNL were able to collect several hop plants from across NE that were remnants from travelers, settlers, or planted in gardens by initial landowners. These plants are currently being screened to learn more of the parental linage, as well as, evaluated for various brewing attributes. Dr. Amundsen and his team have successfully crossed hop plants of interest to those currently being grown commercially. This year they planted the first collection of offspring for growth evaluation in the field. These plants will have their gender identified, evaluated for growth characteristics and susceptibility.

Timely Topics from across Nebraska

• Growth Progress
• Fertilizer Application
• Irrigation
• Insects in the Hop Yard
• Downy Mildew Treatment

Growth Progress

Warmer temperatures and more sun is a welcome site to hop growers across Nebraska.  Regrowth following April cutback was slow given cool temperatures and the ongoing rainy weather.  Differences in varietal vigor are quite evident while scouting the hop yard. For most varieties training should be completed, however, late or lagging varieties might just be in the final walk-thru for completion.  Generally speaking, most varieties are 5-6’ up the strings with more vigorous varieties like Chinook at half trellis or more.  If your hops are near 5’ today (June 7) and with the projected 10-day forecast, plants should be at top of trellis by our target of June 22.

Fertilizer Application

Hops are in the high demand for nutrition at this point.  With optimal conditions, plants can grow more than 12” a day.  It is important to consider the amount of N required based upon your soil fertility test.  I discussed previously in this blog how to think about fertilizing your hop yard based upon a per plant basis.  Note in the following table from Rybacek (1991) that there is 71% N in the above ground plant growth on July 12. 

In Rybacek’s (1991) project, the harvested plant dry weight (DW) on August 23 was 802.09 g, containing 17 grams N or 2.1% of the total DW. Each plant has accumulated approximately 12 g N on July 12, being approximately 26.5 pounds per acre for 1,000 plants.  This was calculated for a plant with a projected ½ pound cone harvest.  The N need would be much higher for plants having a 1-pound harvest, being 63.9 pounds N/acre, or a 2-pound harvest, 132 pounds of N/acre.  This would need to be dosed during the rapid growth period from June 1 through July 12.

Irrigation

Similar to fertilizing hops, water must be available to meet the needs during rapid plant growth and cone maturation.  The number of irrigation events and the total amount of additional water provided will vary greatly between hop growers depending upon soil and environmental conditions.  In more arid climates, a single hop plant will require approximately 175 to 200 gallons of irrigation water during the growing season.  This approximates to 31” of rainfall or irrigation to the root zone.  The irrigation requirement falls mainly from May 25 through September 5, being approximately 15 weeks.  One could use this as a target of 2” of rain must fall or 5 ½ gallons of water is needed per plant per week.

Insects in the Hop Yard

Hop Flea Beetle- these little bronze to black metallic beetles feed early in the spring causing  “shot-hole” leaf injury.  They mate during May and June, eggs are deposited within the top 1” of the soil and the hatched larvae then feed on roots for approximately 4 weeks.  In late summer, adults emerge following pupating and feed on low-growing foliage before over-wintering.  It is not common for this insect to cause economic damage to the hop crop.

Aphids- pressure from adjacent crops may result in these small, pear-shaped and soft-bodied insects to feed on succulent plant growth.  The adults feed through piercing-sucking mouthparts that they use to remove water and nutrients from plant tissue.  Given the aphid feeding mechanism, they can easily spread virus’ from one plant to another.  Aphids can be found in soft new tissue and underside of leaves.  Heavy feeding will result in a sticky sap substance to collect on foliage below and development of a black dusty material called sooty mildew.  This insect does not have an economic threshold but should be monitored given the potential to spread virus and causing damage to hop cones.  Often aphid populations diminish with heat and dry atmospheric conditions.

Leafhopper- this insect is a light green, wedge shaped insect that moves quickly on the underside of hops and adjacent plants.  They often scatter sideways upon first observation and then quickly jump away.  The leafhopper has piercing-sucking mouthparts that penetrate to the vascular system.  Feeding interrupts phloem transport and eventually can affect the xylem, appearing as edge yellowing and leaf curling.  There can be three generations of hoppers per season, and given their wide range of host materials, can be an on and off again problem throughout the year.  There are no economic thresholds identified for this plant but elevated levels of prevention and control should be done on young hop yards until plants are well established.  Broad spectrum insecticides will work to control this pest however care must be given to not excessively apply them or other insect pressures might result.

Lady Beetle- these beneficial insects appear first as alligator like larvae and then will become the traditional looking, large round red with black spotted beetle as an adult.  These insects provide great suppression to aphids, mites and thrips so should be encouraged through a holistic production approach. A mean of one adult lady beetle per second or third plant indicates a healthy population for biological balance in the yard.

Downy Mildew Suppression

Our variety trial in Sutton, NE was devastated in one week by a downy mildew (DM) infection as a result of last years late season occurrence and not using a preventative fungicide treatment this year.  We had observed early symptoms of DM in our Norfolk, NE plot two weeks ago and immediately began spraying sodium bicarbonate (baking soda) sprays every 5 days at 1 Tbs/gallon.  This was an “emergency” situation until we could acquire copper based fungicide (Kocide 3000).  Of interest however, is the following graph showing how the disease was suppressed by using this simple control. 

Field Day in the Hop Yard

Hop Yard Field Day– Saturday, June 22, 2019.  9 am – 12.  Oak Creek Hops near Kearney Nebraska

This first day of summer is the fitting choice to hop over to Oak Creek Hops where farm diversification brought hops to central Nebraska! Oak Creek Hops desires to build strong relationships with community by providing locally sourced products to craft breweries in the area.  In this field day visit, we’ll have Dave and Lisa Gleason talk about their hop yard and how their season is shaping up.  You’ll have the opportunity to network with other growers and share experiences and ideas.  RSVP by registering at ->     https://go.unl.edu/hops-field-day-2019

Timely Topics

• Train and Train Again
• Weather Events
• Chemical Injury
• Disease Prevention and Suppression
• Japanese Beetle
• Field Day in the Hop Yard

Train and Train Again

Target period for hop training in Nebraska is between May 15 and 25, however, may differ somewhat based upon individual growers experience, predicted weather, and hop variety vigor.  The goal is to train two or three (maximum) shoots per training rope to maximize productivity through a balancing nutrient/water needs from the perennial plant portion and optimizing environmental conditions of annual plant growth for general plant health.  Training is not a “once and done” project but plants should be monitored during scouting to verify that they remain trained and that additional shoots did not self train more than desired.  Chinook and Cascade are vigorous varieties that we have seen self-training more shoots than we wanted.  Rather than trying to remove them, we just snap out the apical bud of the shoots we no longer want to continue up the strings.  Additionally, some shoots may fall off of strings early after training in response to windy weather or strings that were not affixed securely to the ground and have too much movement in them.  Once the shoots have wrapped the strings and traveled at least 2-3 feet upward, training can be considered successful.

Weather Events

This has become an active spring, dropping large amounts of rain across Northeast and Eastern side of Nebraska.  Western Nebraska saw accumulating snow when we were desiring to train hops, and once we did train, a serious storm shooting East off the Colorado mountains broke tips and created much injury to the new foliage.  Though the target training period is passed, a harvestable crop is still possible by finding new growth that was undamaged and of trainable length.  The sooner you can replace injured plants the better.  Considering Nebraska has many warm days to come in early June and that hops can grow as much as 12” a day during heat, we can potentially hit the top wire in 18 days.  We’re only 18 days from summer solstice so, “you better get a hop on it!”

Chemical Injury

A challenge by hop growers surrounded by traditional agriculture is that from chemical injury drift that injures hops.  Understanding adjacent land uses prior to establishing a hop yard is critical.  Many of today’s farmers outsource some of their activities as specialists, such as chemical applicators, can do the job more economically.  Unfortunately, there are many enterprises that may or may not have the ethical or environmental concerns that the most professionals would have. Make sure to interact with your neighbors and see is a plan can be developed that allows for both of your agricultural enterprises to succeed.  You can also register your farm with DriftWatch (https://ne.driftwatch.org/) whose goal is to create a voluntarily communication link between crop producers, beekeepers, and pesticide applicators to protect specialty crops.

Once chemical injury has happened on young hop growth, it typically will not recover to continue its upward growth. The best option is to hope that new trainable shoots will emerge and that they can be encourage to grow upward.  The window for re-training is closing quickly as we are only 18 days from summer solstice.  Following that date, the plants will begin flower initiation and will end their upward growth.

As far as the health of the underground wood, it will be important to maintain whatever vegetation you can that does regrow, even if it is not trainable.  This foliage will be responsible for providing new carbohydrates for the health of the perennial wood.

Disease Prevention and Suppression

There has been much Downy Mildew pressure observed this year and the long-range weather forecast indicates that conditions will be optimal for fungal growth.  Hop varieties have differing levels of susceptibility and tolerability to infections.  The grower cannot control rain events but definitely will need to create an integrated crop management plan (ICM).  It will be important to apply preventative fungicide applications routinely to reduce the spread of disease susceptible varieties.  Once the plants are nearing the top wire of the trellis, consider leaf stripping the lower foliage chemically or through other natural methods.  If a chemical strip is used, make sure to use spray shields that direct the application only to foliage and reduces that amount that can reach the stems so they do not get injured.

For chemicals approved for downy mildew on hops: http://www.kellysolutions.com/ne/showproductsbypest.asp?Pest_ID=FFABPEA03

Nebraska Department of Agriculture search database for registered pesticides:  http://www.kellysolutions.com/ne/pesticideindex.htm

Japanese Beetle

This last week I had an inquiry about controlling Japanese Beetles in the hop yard.  Thinking about the adult beetle, my initial response was it is too early and we generally do not control for them.  Control of the larvae is a totally different matter as these are found as grubs feeding on grass roots in the soil.  So, once again, not something we really do in a hop yard.  Urban landscapes typically are treated for grubs, and this includes those that will emerge as Japanese beetles.  Unfortunately, we cannot treat everywhere so this beetle potentially can become a pest sometime in July through the first part of August. 

Japanese beetles tend to aggregate, feed, and mate in large groups, causing severe plant damage in localized areas before moving on other plants.  They feed on a wide range of landscape plants so control is difficult.  Plant injury is typically on the top of the plant and feeding appears as skeletonizing between veins.  When a plant is heavily infested, the beetle may remove all of the green vegetation.  There are many registered pesticides for Japanese beetles and treatment involves early identification and immediate control measures.  Most of the chemicals used are broad-spectrum types and can exacerbate pressure from other insects and mites.  

Research has indicated that adult Japanese beetles can be knocked back with broad spectrum organophosphates (such as Malathion) and pyrethroids (including, bifenthrin and betacyfluthrin), however these products greatly affect beneficial insects. 

For a complete list of chemicals approved for adult Japanese beetles:

http://www.kellysolutions.com/ne/showproductsbypest.asp?Pest_ID=INBPAZJ04

Field Day in the Hop Yard

Hop Yard Field Day– Saturday, June 22, 2019.  9 am – 12.  Oak Creek Hops near Kearney Nebraska

This first day of summer is the fitting choice to hop over to Oak Creek Hops where farm diversification brought hops to central Nebraska! Oak Creek Hops desires to build strong relationships with community by providing locally sourced products to craft breweries in the area.  In this field day visit, we’ll have Dave and Lisa Gleason talk about their hop yard and how their season is shaping up.  You’ll have the opportunity to network with other growers and share experiences and ideas.  RSVP by registering at ->     https://go.unl.edu/hops-field-day-2019

If you have any questions, contact Stacy Adams, Nebraska Hop Extension. sadams1@unl.edu

Timely Topics:

• Statewide Update
• Insect Pressure
• Downy Mildew
• Field Activities

Statewide Update

Conditions in Nebraska have generally been seasonal and hop regrowth from cutback has been uniform with the exception of the Panhandle that had more than 2″ of wet snow this week on hops that were ready to be trained. Increased cloudiness, cool temperatures, and occasional rains have placed significant disease pressure on dense regrowth that has not been trained. It is important that prevented measures are implemented to control the spread of disease now and to prevent problems later in the season. Hop training in Nebraska should be done for early harvest cultivars and completed by May 31 for all others. Weather conditions in the NE Panhandle may delay training until trainable shoots can be identified following the recent weather event.

Insect Pressure

There are several insects that can cause harm to hops but pressures vary seasonally.  Most hop insect pests are opportunist feeders and not specifically a pest of hops.  Hops are not the most enticing plant for insects, but under the right conditions, a pest may proliferate the hop yard and causing enough damage that may reach economic threshold levels.  It is important to scout the hop yard at least on a weekly basis to note incidences of pests and approximate pressure.  Identify which insects are true pests and those that are beneficial predators as often the hop yard ecosystem will attempt to balance the population.  Pesticides should be used when there are indications escalation of pressure that damage would potentially affect crop value.  As with all pesticide treatment plans, apply only chemicals approved for the crop, in the appropriate manner and in accordance with the pre-harvest interval requirement.

Plants in the statewide cultivar trial have generally not indicated pest insects, with the exception of our Norfolk site. In our Norfolk plot, damage is evident from hop flea beetle as shown below and we have seen the presence of potato leaf hopper, but no damage.

Injury from hop flea beetle occurs from overwintering adult insects feeding on the tissue, creating individual holes as seen on the image above. Injury is typically limited to the bottom 3′ but may be higher in the canopy with increased pressure. This pest is not typically economically damaging and the plants typically outgrow this injury later in the season. These adult beetles lay eggs at the base of the plant, which hatched larvae do feed on roots until emerging as adults mid summer. This second flush of adults may feed on cones developing on the lower portions of the plant canopy and rarely require pesticide treatment but populations and feeding injury should be monitored.

Hoppers feed on many species of plants and may be found in hops. They will move in and out of the field, making chemical controls difficult for this insect. Rarely will it cause significant economic damage, however, heavy feeding can cause hopper burn as the season progresses and in extreme cases reduce the general vigor and productivity of the plant due to reduced photosynthesis. Michigan State University provides an excellent resource on this topic. https://www.canr.msu.edu/news/michigan_hop_update_july_8_2014

Downy Mildew

Downy mildew is a major disease of hops that requires diligence in prevention through yard cleanliness and chemical controls. Plant quality and yields are reduced from serious cases of infection. The severity of infection varies seasonally but infections are encouraged by mild to moderate temperatures (60F – 85F) when free water moisture is present for 1.5 – 2 hours for leaf infection and 3 – 6 hours for shoot infection. Excessive outbreaks can result as conditions persist without drying out. It is therefore important to prevent outbreaks through application of a preventative fungicide and reapply as indicated by the product. Organic growers are limited in products to use, however, copper based products appear to provide best efficacy. Read more from Michigan State University on Downy Mildew in Hops: https://www.canr.msu.edu/news/managing_hop_downy_mildew_early_in_the_season_is_critical

Field Activities

Hop training should wrap up within the next week, however, scout the field often for the need to retrain tips until they have a firm hold during more rapid growth. Under windy conditions, tips may fall away from the ropes so verify they continue to track upward. The shoot tips grow at such a rapid rate that they will be brittle, for this reason, injury from hard rains and strong winds my occur. New shoots can be trained from the lowest portion of the plant, however, side arms cannot be trained to replace a broken tip. Even if the training date has ended, some productivity can occur on late trained shoots.

Crop scouting should be completed weekly (at a minimum) to visually inspect for;

• Insect identification of those that are pest or beneficial
• Monitor disease and insect pest pressure
• Verify irrigation systems are functioning correctly
• Visual inspection to monitor nutritional needs
• Plants remain trained and development progress

Make sure to connect with others at-> https://agronomy.unl.edu/nebraska-hops

with lots of work and temperatures pushing rapid growth!

• Field Notes
• Hop Cut Back Recovery
• Nutrient Requirements
• Disease Pressure
• Hop Bine Selection for Training
• Workshop Opportunities

Field Notes

Hop growth is significant with the increase in temperatures across Nebraska.  Season programmed cut back should have been completed by the end of April.  Plants that were missed should not be cut back at this point given top growth would have placed significant drain on energy reserves in the underground wood.  Timing of growth can be adjusted through carefully selecting bines to train on the ropes in the coming week.  Weather across Nebraska has been remarkable to this point for optimal plant development and growth, however, spring is typically when severe weather events can occur and coincides with when hops are most vulnerable.  Make sure to read later in this post about Hop Bine Selection for Training and learn which bines can be used for possible replacement if the terminals get broken.

Hop Cut Back Recovery

Our campus quarter-acre hops plot using a traditional trellising system was cut back on April 25.  The following graphic provides regrowth measurements for three plants of each cultivar per replication taken three weeks following cutback.  The most vigorous regrowth was noted for Chinook and Cluster with Centennial, Crystal, and Zeus recovering well but quite variable.  Perle is slow to regrow from cutback, having many short stems that are not as vigorous as other cultivars.  Perle is typically considered to have a high growth rate and commonly grown however has consistently not performed well in Nebraska’s conditions.

The variety trials across Nebraska were cut back on April 28-29 with no notable differences to the regrowth noted at the campus quarter-acre plot.

Nitrogen Nutrient Requirement

Initial growth observed in hops draws upon nutrients stored in the underground perennial wood.  During the spring rapid growth the plant requires many macro and micronutrients to maximize its growth.  The nutritional requirements change over the course of vegetative development through flowering and cone development.  The following table from Rybacek (1991) demonstrates the changing elements in the above ground hop plant portions. Dates are noted as day.month.  Note that calcium, potassium, and nitrogen are taken up in very large quantities during this ten-week period.

It is important that nutrients in the soil are made available to meet the plants needs during the growth period.  Harvesting of the seasonal plant growth (bines, shoots, leaves, cones) will remove nutrients and must be replenished for continued regeneration of annual plant growth and maintenance of the underground perennial plant structure.

The question of how much nitrogen (N) fertilizer to apply annually is not an easy answer.  General recommendations for hops indicate that approximately 150 pounds of N per acre should be provided. The following demonstrates how one should potentially determine what their true N application rate should be;

Example: Grower with 1,000 plants on an acre

• Total decapitated per plant dry weight (DW) at harvest:  1,361 grams (g)  
• Projected cone dry weight from plant harvested (~33% total DW):  449 g  (~1 pound)
• Amount of N removed in decapitated hop plant (~2.1% of plant): 28.58 g
• Number of plants removed on an acre (variable by grower): 1,000 typical
• Amount of N removed per acre:  1,000 plants x 28.58 g N= 28.5 kg or 63 lb(#) N removed

As expected yield/annual vegetative growth changes, so does the N requirement. Using the same 1,000 plant per acre example, consider a highly performing variety which has an expected 2.2# cone harvest;

• Total decapitated per plant dry weight (DW) at harvest:  3,024 grams (g)  
• Projected cone dry weight from plant harvested (~33% total DW):  998 g  (~2.2 pound)
• Amount of N removed in decapitated hop plant (~2.1% of plant): 63.50 g
• Number of plants removed on an acre (variable by grower): 1,000 typical
• Amount of N removed per acre:  1,000 plants x 63.50 g N= 63.5 kg or 140 lb(#) N removed

To optimize productivity, it is critical to consider the potential harvest of the crop to approximate the amount of N needed for the plant.  The farmer tested the soil and received the following results from the lab;

Note that 36# N is found in the soil, but most likely not all would be available.  The grower would want to provide at the very minimum the difference between that required for the expected harvest and that available in the field.  In this case, the grower would want to provide at least 27# N for plants having an expected harvest of 1# cones and 104# N for plants having 2.2# of cones at harvest.

No matter the fertilizer rate that is decided by the grower, it is important to apply the nutrient to the area of the plant root zone.  It is important to calibrate the application rate to provide the desired rate on a per plant basis and less emphasis on a per acre rate.

Disease Pressure

Increased rain events during spring greatly increases the occurrence of disease if water droplets remain for extended periods on time on the foliage. Most Nebraska hop producers have very good air movement through the hop yard which reduces the conditions for suitable for large disease outbreaks. Make preventative fungicide treatments as instructed on individual products and use spreader/stickers as recommended to improve effectiveness.  Use only drip irrigation methods in the hop yard and consider doing a chemical burn off of lower 24-36” of vegetative leaves when plants near the top wire.

Hop Bine Training

Initial spring growth characteristically is vigorous with long internodes and is removed at the period of the timed cutback. Secondary buds are then encouraged to grow, having a bit less vigor and with shorter internodes then the initial growth, they result in a fuller mature plant with more flowering side arms. It is important to carefully choose which shoots to encourage for training on the programmed training date. It is best to train new hop shoots that emerged following early season cold conditions have ended and the shoots are nearing 20-24” long.  Avoid delay as yields can be greatly reduced by late training.  Optimal training for Nebraska generally appears to be between May 15 and 25 but can varies by seasonal temperature variation.

It is recommended that only two bines be trained per rope and a maximum of four bines total per plant.  Bines not trained should have the tips removed to prevent self-training and excessive energy draw from the underground perennial plant.  Hop bines naturally rotate clockwise and also are fragile so carefully handle them when selecting and encouraging them to wrap the trellis rope.  They only need to be resting against the rope and will naturally begin binding on their own within a few hours after making contact.

Workshop Opportunities

Don’t forget to attend one of our educational workshops.  This is a great time interact with Nebraska Extension and network with other growers. I hope to see you soon!

Upcoming Events

• Introductory Hop Workshop May 31  https://go.unl.edu/hops workshop-2019
• Hop Training Field Program May 31 https://go.unl.edu/hops-training-2019
• Hop Yard Field Day- Oak Creek Hops https://go.unl.edu/hops-field-day-2019

• Hops Growth Progress Across NE
• Determination of Cut Back Timing 
• Fertility
• Weed Control
• Disease
• What’s Next?

Hops Growth Progress Across NE The UNL Hop Cultivar trial plantings are located at UNL East Campus in Lincoln, near Norfolk, at Panhandle Research and Extension Center in Scottsbluff, and a location in Sutton (outside of Hastings).  Cultivars included in this statewide project are Columbia, Centennial Chinook, Cluster, Crystal, Perle, Willamette, and Zeus (CTZ).

We have seen generally uniform emergence at all locations, most being 12-16” in height on April 29.  We are not seeing any indications of diseases at the present time.  Plants in the trial were cut back between the dates of April 25-29.  These plants are beginning their third season of production.  The growing beds are 4’ wide and were edge cut to improve drainage in locations with heavier soils and to prevent rhizomes from encroaching the aisles.  Following is a hand power tool we used for the trial sites, each location has 96 plants with 32 plants per row spaced 1 meter apart. You’ll note that the plants were cut back and were marked to verify original plant locations for the coir ropes.

Determination of Cut Back Timing  For those of us in the Great Plains States, picking the appropriate date for a spring cut back is challenging.  The question some of you may have is, “why is there a spring cut back?”.  The following summarizes the key principles for doing so;

1. The cut governs the sprouting period to create a uniform crop
2. The annual cut greatly limits outward growth of the underground plant portion.  The aids to prevent the plant from growing into the main aisles. 
3. It reduces the area producing bine stems to aid in the training process.
4. Spacing of plants remain consistent which improves irradiance of light through the canopy of the hop yard, resulting in more uniform cone development and quality
5. The underground wood remains at proper depth and does not migrate upwards 

The timing will vary by variety and the differences in weather annually. Varieties that exhibit robust spring growth will need to be cut back before the new growth becomes mature.  This is loosely at the 18″ – 24″ length when the spiraling of the tip initiates.  Too much of a delay in cut back will reduce new growth rate and may prevent the plants from reaching the top of trellis.  It has been additionally noted that flowering and cone development will be greatly restricted, much more than that expected of a plant of similar size but cut back on an earlier date. 

In 2018, the warm spring temperatures accelerated growth early before our scheduled cut back in the variety trial.  We made cut backs after the stems were transitioning to adult wood, greatly affecting regrowth and training.  This was apparent for the variety ‘Centennial’, exhibiting that a 4 day delay in cut back was the difference between having productive plants and those that only made 1/2 trellis with very few cones.    
Many resources indicate April 25th as the latest cut back date with training by May 25th.  If you have not made your seasonal cut back, I would do so before long.  This will allow for regrowth that stems can be selected for training around the 3rd week of May.  Those not trained can be tipped to prevent continued growth.

Fertility A soil analysis test should be performed to determine nutrient availability.  Much of NE soils are fertile so often the most limiting nutrient will be nitrogen and can be provided in many different sources, the least expensive being urea.  When growing in sandy soils, a more complete nutrient formulation will be necessary.  During the initial spring growth, nutrients are being drawn from that which is stored in the underground wood from the previous season.  The supplementation of that should be done during the most rapid growth period, that being during the period of June to the end of July.  More detailed information about nutrient application will be provided in the next Hop Grower Update.

Weed Control It is critical to manage the weeds during the first two years of the hop yard so that the plants can be established. New growers may hoe around new plants but also have found fabric mulches to work well as this reduces the use of herbicides that may affect the development of the plant.  Once the hops are established, mulches are typically removed to allow for management of the plants using typical cultivation methods. Larger hop yards and those with established plantings generally use chemical methods.  It is important to only use chemicals that have an approved label for use in hops.  

Disease If you had disease last year it is important to do a clean up of the hop yard during the cutback period.  In central and eastern NE, optimal conditions occurred for Downey Mildew and there were several outbreaks throughout June and July, which is not typical for our typically windy and dry period.  Make sure to remove all previous season stem and leaf debris, as well as, the new growth being cut during the timed cut back. This material should be removed from the hop yard and composted for other uses and not returned to the hop yard.

What’s Next? Some things to begin doing while you have time;

• Make sure the irrigation system is working.  Check for leaks from rodent injury or damage during the cut back process.
• Get a soil fertility analysis done.  Collect multiple core samples that are through the top 12″ profile.  Mix these together as a general representation and send to a lab for analysis.  
• String coir ropes but don’t insert them into the soil yet unless you want to remove self-trained bines!
• Make connections with your local brewers and develop a relationship.  Learn more of what they desire in locally available hops and invite them to your farm.  Offer them a free sample of hops to try and buy.

Upcoming Events

Introductory Hop Growers Workshop May 31  https://go.unl.edu/hops-workshop-2019

Hop Training Field Program May 31 https://go.unl.edu/hops-training-2019

Hop Yard Field Day- Oak Creek Hops https://go.unl.edu/hops-field-day-2019