The Effect of Edge-spraying a Broad-spectrum Insecticide to Control Hop Arthropod Pests while Retaining Beneficial Arthropods

Aroostook Hops, Westfield, ME

Project Summary (full report available at

The purpose of this project was to determine if a broad-spectrum OMRI-certified insecticide can be used to control major pests of hops (including leafhoppers) to increase hop productivity without creating other pest management challenges or a reduction in beneficial arthropods. We used pyrethrin treatment in a one- and three-acre hopyard in several different regimes culminating in a final year of complete pyrethrin coverage. We sampled arthropods, plant biomass and yield, and hopperburn to determine if spray regime or location (edge versus interior) impacted measures of hop production and management. There was evidence from all three measures that pyrethrin positively impacted management of hops pests and improved yield in hops, without resulting in other pest management issues. Thus, we will continue to use and evaluation pyrethrin to target pest populations and we advise other farmers to consider this approach. However, there is evidence that leafhoppers are able to rapidly repopulate small hopyards and potential evidence of selection for resistance to pyrethrin treatment. Thus, this approach should utilize arthropod sampling or scouting to monitor effectiveness.

Summary of Important Findings

  • Pyrethrin application may greatly reduce leafhopper abundance (although the effect may be short-lived)
  • Plant biomass and wet yield was higher in pyrethrin treated plots
  • Few to no aphids or two-spotted spider mites were detected during these years or in relation to pyrethrin application
  • The predominant leafhopper pest was NOT potato leafhopper (Empoasca fabae), but was a similar species in the genus Hebata (formerly Empoasca)
Figure 1: count of leafhopper abundance on Cascade hops (above) or total beneficial arthropods (below) on sticky cards (Y-axis) versus sampling events (1-10) from early June to early September with Pyganic applications indicated by an arrow. Samples are from north (CAW1) or south (CAW41) hopyard edges or interior (CAW17). Figure 2 is below.

This material is based upon work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, through the Northeast Sustainable Agriculture Research and Education program under subaward number FNE21-977. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

4th Annual Industrial Hemp Conference

The University of Vermont Extension Northwest Crops and Soils Program and the Vermont Agency of Agriculture, Food & Markets invite you to the Fourth Annual Industrial Hemp Conference (click to view the conference brochure)! All information is also available at

This event will be held virtually over two days – Tuesday, March 15, 9am—1pm and Wednesday, March 16, 12:30—4:30pm. Cost is $50 per person. Register here today! Or call in to register at 802-656-5665 ext. 3. Registration ends at noon March 11.

Growers can hear from leading experts about hemp market trends, variety improvements, grain and fiber hemp production, pest and disease management, federal grant opportunities and much more. In addition, a Vermont Cannabis Control Boardrepresentative will provide an update on a state regulatory program for adult-use and medical-use of cannabis in Vermont.

Day one will include a plenary session featuring Jane Kolodinsky, UVM, and Tyler Mark, University of Kentucky. They will present information on the National Hemp Acreage and Production Survey, hemp trends, consumer knowledge, economics and markets. Day two keynote session features Stephanie Smith and Michael DiTomasso, VAAFM, who will discuss the implementation of new U. S. Department of Agriculture (USDA) hemp rules and changes growers can expect in regulation and compliance.

Certified Crop Advisor and Pesticide Applicator continuing education credits will be available.

To request a disability-related accommodation to participate, contact UVM Student Accessibility Services at or (802) 656-7753.

Our current conference sponsors include –  

Hop Sensory Training Courses

UVM Extension Northwest Crops and Soils program is hosting “The Basics of Descriptive Sensory Analysis” 2021 Sensory Training course. UVM Extension’s sensory expert, Roy Desrochers, will be the instructor for this interactive comprehensive six module virtual training program, that will be held Tuesday and Thursdays from March 30 to April 15, 8:30am to 10:00am.

The program was initially offered to hop growers, and we are now opening 15 additional spots for hop brewers. You must register by this Friday, March 19th by 4pm. As this program, that teaches the basics of objective aroma and flavor evaluation, is interactive, we need to have time to mail you a box of supplies before the first module on March 30.

View the Sensory Training Course flyer. Cost is $200 per person. You can register online here or call UVM’s Non-Credit Registrar’s office at 802-656-8407 by Friday, March 19 at 4pm. Remember, registration is capped at 15 brewers.

Japanese Beetles in Hops in the Northeast

The Japanese beetle (Popillia Japonica) can be a significant economic pest in Northeastern hop yards. Japanese beetles begin to show up in Vermont at the very end of June or early July, and are most active on warm, sunny days. We spotted a Japanese beetle in our hop yard at Borderview Farm on July 1. Japanese beetles can be found feeding on the fruits, flowers, and foliage of over 200 plants. Hop leaves damaged by Japanese beetles are skeletonized, with only the veins left behind. The adult is an oval-shaped beetle with a metallic green body, copper-colored elytra (hard front wings) and tufts of white hair along its abdomen. Japanese beetles overwinter in the soil as white C-shaped grubs, where they feed on the roots of many crops, though they are not known to cause significant damage to hops as grubs.

Adult Japanese beetle

Read the full fact sheet on Japanese beetles on our web site –

There are several conventional and OMRI approved chemicals that can be used to manage Japanese beetle adults in Northeastern hop yards. See Table 1 in our factsheet for a list of approved insecticides for Japanese beetles on hops in MA, NY and VT for 2012. This list is not exhaustive; please check with your local Extension service or Agency of Agriculture. When using a pesticide, be sure to read the label in its entirety. It is illegal to use a chemical in a site or on a pest for which it is not specifically labeled. Be sure to adhere to pre-harvest intervals and use proper personal protection equipment. It is always advisable to try out a new pesticide or tank mix on a few plants to evaluate a crop’s reaction before spraying the whole yard. Also note that there are some varietal differences in reactions to certain pesticides.

Most insecticides will not only kill target pests, but can also be damaging to beneficial insect populations. When applying an insecticide in your hop yard, always be aware that eliminating beneficial insects can lead to secondary outbreaks, when a less abundant pest is given an advantage by removing its natural enemies. The hop burr is very susceptible to mechanical damage during pesticide applications, so if at all possible, try to avoid spraying during burr development. Instead, spray just prior to flowering and use a product that is a very effective protectant with a long residual period.

In addition to chemical controls, biological control of Japanese beetle grubs can be very effective. There are several beneficial nematodes, which are commercially available, and applied as a soil drench. Another effective biological control of Japanese beetle grubs is the milky spore bacterium (Bacilluspapillae), which comes in the form of a powder that can be applied to the soil.

Potato Leafhoppers have Arrived!

First, second, and third instar potato leafhopper nymphs.
First, second, and third instar potato leafhopper nymphs.

It is leafhopper season again and those pesky insects have been spotted at our research hop yard at Borderview Research Farm, in Alburgh, Vermont. This is a great time to start scouting for insects as well as for disease to ensure proper management of all hop pests. So far, this season has not been conducive for the hop pests that thrive in wet conditions, such as downy mildew and aphids, but the potato leafhoppers have arrived right on schedule. Potato leafhoppers are migratory insects transported via wind currents from the southern United States, generally appearing in the Northeast between late-May and mid-June. Our first sighting was on June 10, 2020.

To scout for potato leafhoppers, examine the back of a hop leaf for little torpedo shaped insects with distinctive green coloration. Young potato leaphoppers, or nymphs, are flightless insects and can be seen scuttling around the leaves in a side-to-side fashion. Adults can also be scouted by checking the backs of the leaves, or for a easier approach, you can just give your plants a little shake and watched the adult potato leafhoppers fly off the plant or jump from leaf to leaf. At our hopyard, we have only observed adults so far, but that means the nymphs aren’t far behind. Within one season, there are usually two or three generations of leaphoppers present in northern hop yards.

Hopperburn: visual V-shaped chlorosis injury caused by potato leafhopper.
Hopperburn: visual V-shaped chlorosis injury caused by potato leafhopper.

Potato leafhoppers are an economically damaging pest that can cause hopper burn, which is a distinctive yellowing of the leaves in a V-shaped pattern, eventually leading to leaf tip necrosis. Hopper burn decreases leaf photosynthetic activity and can cause plant production to suffer. One of the best ways to combat potato leafhopper damage is by planting an alfalfa or red clover trap crop. Potato leafhoppers prefer to feed on these legumes and can be redirected from your hop yard with strategic plantings on the outskirts of the yard or in the drive row.

For more information on PLH management in hops, see the following resources:

Potato Leafhopper in Northeastern Hopyards fact sheet.

Vermont Hops Power Hour, 6.26.2017, Potato Leafhopper

Field Guide for Integrated Pest Management in Hops (

Stay vigilant and keep scouting!

Early Season Management

Now is a great time to prepare for the upcoming season as plants are beginning to come out of dormancy. If you haven’t ordered your coir for the season, now is the time to do so while also taking inventory of other necessary tools and supplies such as w-clips, applicators, and pruners to name a few. Work in the hop yard in Alburgh, VT has picked up with the recent warm weather. We have begun cleaning up our hop yard from any existing debris and supplies have been ordered. As we near the fast approaching season, there are a number of activities that can prepare you in the hop yard if you haven’t done so already.

Early season in the hop yard.

– Order necessary supplies.

-Clean and disinfect tools.

-Submit a soil test for fertility guidelines for the upcoming season.

-Develop a proposed schedule for fertility applications based on these soil test guidelines.

-Check irrigation system and patch or replace broken lines and valves.

-Remove any residual debris from previous season.

-Repair damaged trellis. –

– Check equipment and perform necessary maintenance.

As the spring progresses the necessity to prune will arrive quickly as well as the need for stringing plants to set your plants up for success. With plants a few weeks ahead of last year (which got off to a slow, wet start) crowning has been completed on our research plots with future plans to flame prune a few weeks away.

Some additional links for information:

Managing Downy Mildew in Hops in the Northeast,

2019 Hop Crowning Trial,

Mastering Spring Activities in the Hop Yard with Julien Venne (video presentation),

Hop mechanical crowning.

What to be on the lookout for in your hop yard

The three major arthropod pests of hops in the Northeast are Potato Leafhopper (PLH), Two-spotted Spider Mites (TSSM), and Hop Aphids (HA). This incidence of these pests in hop yards is based on the weather conditions, and we found that the hop aphids preferred cool and moist conditions and populations peaked around the time of harvest through September. For more information about disease, weed, and insect pest populations, check out our six-year study, Organic Hop Variety Trial .

Hop aphids (Phorodon humuli) are small soft-bodied insects that come in both wingless (immature individuals) and winged (adult females) forms, both of which are found on hop plants. Hop aphids are pear shaped and range in color from pale white to a yellowish-green and are found on the underside of the hop leaf. They do not over winter on hops, but rather on a variety of plants in the Prunus genus (Family Rosaceae). Hop aphids over winter as eggs and in early spring the eggs hatch and reproduce asexually for one or two generations before the winged form migrates to hop plants in May. 

These small insects have piercing-sucking mouth parts that are used to feed on the hop leaves and cones, and suck the phloem from the plant. This can cause leaves to curl, and turn cones brown and limp. Hop aphids also release a sugary substance called “honey dew”, which allows for the growth of sooty mold fungi on the hop leaves and cones. While leaf feeding can decrease the marketability of the crop, the bigger threat to hop yield and quality is the sooty mold which results in aesthetic cone damage and a decreased cone quality.

It is important to start scouting early in the season and monitor hop aphid populations throughout the season. One way to control hop aphids is the use of natural enemy arthropods. A list of management tactics and natural enemy arthropods can be found in Hop Aphid, Phorodon humuli (Schrank), in Northeastern Hop yards.

Scouting for Downy Mildew

Scouting for downy mildew in the hop yard. Now that the growing season is underway, it is important to be on the lookout for downy mildew! This spring has been very rainy, and the excess moisture on the hop plants creates ideal conditions for downy mildew infections. Downy mildew produces spores in warm, moist conditions and can spread quickly.  Plants are at a higher risk during rainy days because the plant’s stomata, or pores, are open, leaving an open pathway for disease invasion.

Downy mildew is a systemic infection which means that once a plant has downy mildew, it is infected for life. At the end of the growing season, downy mildew will over winter in the crown of the infected hop plant, and re-emerge in the spring.

Infected leaf with downy mildew.

When scouting your hop yard, the first signs of a downy mildew infection are the basal spikes. Basal spikes are chlorotic, or yellowing, and have shortened internodes, or the space between leaf pairs. A severely infected basal spike may also have desiccated leaves.

Other signs of a downy mildew infection are aerial spikes and infected leaves, which will begin to appear as the season progresses. Aerial spikes have the same chlorotic appearance and short internodes as basal spikes, except they’re found on a trained plant rather than on the ground. Infected leaves have necrotic lesions, delineated by leaf veins. These lesions are angular and have very distinct edges, which can help with disease identification.

Downy mildew on basal spikes.

Downy mildew can be managed and there are methods to prevent the spread of infection. When scouting plants, it is important to trim off the infected bines and leaves, and to make sure that infected plant material is removed from the hop yard. If infected leaves have spores, be careful while handling them to reduce the risk of spreading infection.

Increased airflow is another way to reduce downy mildew. It reduces the amount of time your foliage spends wet, which decreases the time that downy mildew is producing spores. Stripping the lower 2 to 4 feet of foliage once a plant is trained and established can reduce moisture.

Biofungicides are another helpful tool to use during the season to control downy mildew, and they can be applied the day before a rain event. There are a variety of conventional and organic fungicides registered for hop use. If you live in Vermont, a list of OMRI-approved biofungicides can be found in the 2016 Hop Biofungicide Trial Research Report.  It is very important to only apply fungicides that are listed in your state for use on hops so be sure to check the label.

Stringing and Training Hops

Stringing often starts in April for many farmers in the Northeast. Stringing consists of tying coir twine to the top supporting wire of the hop trellis and stapling the bottom of twine into the ground next to the hop plant.  Depending on trellising style and setup, 1-4 strings will be run to each crown, though we typically see two in many yards. The strings are inserted into the ground and held in with “W” clips using an insertion tool. This will provide the bines with a means to grow to the top wire in the upcoming season.

Stringing at Champlain Valley Hops in Starksboro, VT.

In commercial hop yards, training dates are determined by cultivar growth in the spring.  Depending on whether a cultivar matures early, mid-season, or late, there is typically a particular range of days for those plants to start their upward growth. Getting the bines off the ground is also important for managing downy mildew and other potential disease issues.

Training dates from 2013-2018, Alburgh, VT.

Year Date
2013 20-May to 27-May
2014 19-May to 30-May
2015 20-May to 26-May
2016 24-May to 25-May
2017 N/A
2018 22-May to 23-May

Training is the process of wrapping shoots around the twine in a clockwise motion. Three to five shoots are selected from the crown to be wrapped around the twine. This process can be time consuming and will play a major role in subsequent plant growth and yield. Choose healthy, vigorous shoots for training that are 2-3’ in length, but avoid training bull shoots. Bull shoots are characterized by having greater internode spacing, hollow stems, and are often purple in color. These shoots will be less productive and more brittle in the wind. The bull shoots do not yield well and should not be trained. Think about leaving some shoots as backups during training.

Regular shoot (top) compared to a bull shoot (bottom).

In general, early harvested hops will have higher yields when trained earlier, whereas late harvested hop will have higher yields if trained later. We look to start training by mid to late May for our early maturing varieties but postponing another week can be beneficial for late maturing varieties depending on growing conditions. In the Northeast, training dates for farmers may fall between mid-May and early-June. We recommend that you make your own observations of hop maturity for each variety and keep detailed records of training dates for your region.

Bull shoots emerging from a hop hill

Crowning and Early Season Downy Mildew Control

Hop downy mildew is currently the biggest disease concern for Northeastern hop growers.  Downy mildew overwinters in the hop crown and primary inoculum will be released from the first shoots. Removal of the infected crown or the first flush of spring hop growth is called “crowning” or “scratching”. Shoot removal is used as an early season preventative measure against downy mildew and as a way of managing harvest time.  Hop plants have been budding out for a few weeks now in Vermont and likely most crowning has already occurred. However, scratching or removal of new growth can still be done and may further eliminate infected plant material. Below are some basic tips for crowning and scratching for our region.

1st year hop yards should not be crowned to allow for root establishment.

2nd year hop yards should be crowned if downy mildew was a problem last season.

3rd year hop yards should be crowned if it can be done in April or very early May.

For early season shoot removal any of the following three methods have been used with success in the Northeast.

1. Mechanically cutting and removing the shoots.

2. Flaming after first flush of growth and shoot emergence.

3. Herbicide application. Make sure any pesticide used in your hop yard is labeled for use in your state and on hops.

Since 2014, UVM has been researching the impact of crowning on hop yield and quality. Check out our Hop Crowning Trial final report update to learn more our results.

Crowning was done in the hop yard at Borderview Research Farm in Alburgh, VT on April 25, 2019.

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