Drought-Stressed Soybeans: Keep an Eye Out for Spider Mites

Jaime Cummings and Ken Wise (NYS IPM), Mike Stanyard (CCE NWNY), and Elson Shields (Cornell Entomology)

soybean field and leaf
Spider mite damage to edge of soybean field and individual leaf (photos by Mike Stanyard, CCE)

Widespread drought conditions are stressing the crops, and may lead to flare ups of two-spotted spider mites in some soybean fields.  We’ve already heard some reports of low to moderate spider mite infestations in a few fields in western NY, and could expect more in coming weeks if the weather stays hot and dry.  If left unchecked, even a moderate infestation can result in 10-15% yield loss.  As with any pest, it’s best to understand why they are problematic and what the best management practices are.

Magnified photo
Two-spotted spider mites through magnifier (photo by Mike Stanyard, CCE)

Spider mites are tiny, eight-legged critters that can spin webs like spiders.  In fact, they spin little web parachutes to catch the wind and blow into your fields.  They prefer hot, dry conditions, where they can reproduce rapidly with multiple generations completed every 7 – 21 days.  Infestations typically start at field margins, usually in the lower canopy, but can quickly spread throughout a field.  The spider mites are difficult to see individually with the naked eye, but their feeding causes obvious damage.  Feeding injury results in stippling (or speckled-like) appearance of leaves, as the mites colonize and feed on the lower surfaces of soybean leaves.  These speckles start out as almost a silver color, but later can turn yellow or brown.  Severe feeding damage can cause entire leaves to become curled and necrotic, reducing photosynthesis, and potentially even resulting in death of severely affected plants.  Webbing will be obvious on the underside of infested leaves, as may be the small, white shed skins from molting individuals.  You can shake a damaged plant onto a piece of paper or hood of your vehicle to knock the mites off to see them.  Check out this video of spider mite activity on a corn leaf by Mike Stanyard, CCE.

Closeup of soybean leaves
Spider mite damaged leaf with mites on webbing, and mites congregating at tip of leaf (photos by Mike Stanyard, CCE)

The mites have piercing-sucking mouth parts, which penetrate the leaves and consume the plant sap, similar to how aphids feed.  This makes things worse for the already drought-stressed plants.  Damaged plants may be prematurely defoliated or stunted, resulting in fewer pods and fewer beans per pod.  This can all happen very quickly when conditions are ripe for population explosions of this pest.

soybean leaf
Soybean leaf heavily infested with spider mites (photo by Mike Stanyard, CCE)

Spider mites are always present at low levels in crops and surrounding weeds or hedgerows.  They are typically kept in check by natural populations of parasitic fungi and beneficial insects.  Unfortunately, the hot, dry weather that favors spider mite outbreaks isn’t favorable for these naturally occurring biocontrol agents.   Staying ahead of the pest by knowing when to expect them and keeping weedy field margins mowed to minimize reservoir habitats are a good way to start.  The best and easiest way to manage spider mites is with persistent rainfall, but we can’t control the weather!  Pay attention to the forecast, and if moderate moisture is predicted, you may be able to avoid taking other action.  But, if the forecast is for continued hot and dry conditions, then you should scout your soybean fields weekly.  There is no specific economic or action threshold for spider mites.  Scouting to catch damage early and knowing the forecast will help you make the best decision on whether or not to spray.  If you catch them early, you may be able to spray just the affected field margin and approximately the surrounding 100 feet to contain them.  For small fields, you may need to treat the entire field.  It’s important to know that none of the insecticides target the eggs, so there may be a resurgence following the first spray if there are many eggs present and if favorable conditions persist.  Below is a table of registered insecticides labeled for spider mites in NY as of July 2020.  Remember to read and follow all label instructions when using any pesticides.

Table of insecticides registered for use on spider mites in NYS

Disclaimer: Read pesticide labels prior to use. The information contained here is not a substitute for a pesticide label. Trade names used herein are for convenience only; no endorsement of products is intended, nor is criticism of unnamed products implied. Laws and labels change. It is your responsibility to use pesticides legally. Always consult with your local Cooperative Extension office for legal and recommended practices and products. cce.cornell.edu/localoffices

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New restricted use insecticide registered for aphids on soybean

Contributed by Mike Helms, Pesticide Management Education Program

The New York State Department of Environmental Conservation (NYSDEC) recently approved the registration of three insecticides containing the active ingredient afidopyrofen. These are the first products registered in New York State containing this active ingredient. Products registered include:

  • Sefina Inscalis Insecticide (EPA Reg. No. 7969-391) – registered for use on several agricultural crops including cucurbits, fruiting vegetables, tuberous and corm vegetables and soybean against various aphids and whiteflies.
  • Versys Inscalis Insecticide (EPA Reg. No. 7969-389) – registered for use on brassicas, leaf petiole and leafy vegetables, pome fruit, and stone fruit against various aphids and whiteflies.
  • Ventigra Insecticide (EPA Reg. No. 7969-393) – registered for use on ornamentals and vegetable transplants against aphids, whiteflies, mealybugs, and scale.

Note that all three of these products are restricted-use in New York State and their use in Nassau and Suffolk Counties are prohibited. The labels for these products also have NY-specific buffer zone requirements.

Copies of the approved labels for these products are available from the NYSDEC’s product registration website.

Questions should be directed to Cornell PMEP.

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Looking for Cereal Leaf Beetle Infested Fields

Contributed by Jaime Cummings, NYS Integrated Pest Management Program

small grains in field
Cereal leaf beetle larva and damage. (Photo by J. Cummings)

Many of you in certain parts of NY experience damage and losses to your small grains crops from the Cereal Leaf Beetle.  It is considered a primary pest of concern wherever it infests a field.  We started a project in 2019 to investigate the potential for biocontrol of this pest, and it yielded promising results, which some of you may have seen shared at various crop congresses and other extension venues this past winter (Fig 1.).

Table of cereal leaf beetle collection
Figure 1. Collection efforts in 2019 to identify cereal leaf beetle parasitoid populations in NY

We confirmed the presence of the biocontrol parasitoid wasp, Tetrastichus julis, in a number of fields in 2019, including a high population of them in one location in Tompkins County (Fig. 2).  Cereal leaf beetle larvae were collected, parasitism levels were determined, and were then released at the Musgrave Research Farm in Cayuga County.  The goal is to build this population of parasitoids and use it as a reservoir for future releases in areas affected by the cereal leaf beetle pest over the next several years.

bar chart
Figure 2. Parasitism levels of collected cereal leaf beetle populations in NY in 2019.

Based on the success of the first year, we are moving forward with this project, and we need your help.  Please help us identify fields infested with cereal leaf beetle larvae.  If your field is infested, please contact your local CCE field crop specialist or Jaime Cummings at the NYS IPM program (jc2246@cornell.edu) so that we can come and collect larvae from your fields to determine parasitism levels and potentially use them to build up the population of the parasitoid at the research farm for future on-farm releases.  We appreciate your cooperation!

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NNYADP Announces New Way to Apply Biocontrol Nematodes

man standing on manure truck
CCE Field Crops Specialist Michael Hunter loads biocontrol nematodes into liquid manure application field trial. Photo: CCE Jefferson County

Farmers now have a new way to apply biocontrol nematodes to protect crops critical to dairy and livestock agriculture, thanks to research funded by the Northern New York Agricultural Development Program.

“Dairy farmers and crop growers have been interested in biocontrol nematodes since we proved their effectiveness at reducing populations of the alfalfa snout beetle, the most destructive pest of alfalfa, and now see potential to do likewise with corn rootworm, a significant threat to field corn production,” said Elson Shields, Ph.D., Cornell University, Ithaca, N.Y.

Shields pioneered the use of a combination of two native NY-adapted nematodes for pest management in field crops, berries, and other crops. The application of biocontrol nematodes is now being tested in multiple crops across the U.S.

In 2018 and 2019, Cornell Cooperative Extension Field Crops Specialist Michael E. Hunter developed a project to test application of the biocontrol nematodes via liquid manure. The current protocol applied the biocontrol nematodes in a water solution in the evening hours due to the nematodes’ sensitivity to U/V rays.

Hunter conducted field trials on 12 farms in Northern New York over the two-year project. He explained the hypothesis behind his trials.

“If biocontrol nematodes could be successfully established through liquid manure application that would accomplish significant benefits: combining two field operations into one to save time and labor, protecting the nematodes from damaging U/V light so application can be made at any time of day versus only evening hours, protecting crops using a biological means, and providing farmers with an additional method for application to encourage use of this biocontrol,” Hunter explained.

Soil sampling in 2018 confirmed establishment of the bicontrol nematodes applied in liquid manure in all trial fields on the six participating farms. In 2019, Hunter achieved successful establishment at a lower rate of nematodes per acre.

“The 2019 field data shows the lower rate of application is just as effective for establishing the biocontrol nematodes and lowers the cost to encourage farmers to adopt the use of this biocontrol,” Hunter said.

The complete “Evaluation of Alternative Application Methods of Biocontrol Nematodes in Alfalfa and Corn” report is posted at www.nnyagdev.org.

Funding for the Northern New York Agricultural Development Program is supported by the New York State Legislature and administered by the New York State Department of Agriculture and Markets. For more information, see www.nnyagdev.org.

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Report Seedcorn Maggot and Wireworm Damage: WE NEED YOUR INPUT

Given the recent controversy surrounding the proposed legislative bans on some pesticides in NY, Cornell researchers and extension specialists are working to provide necessary data on the efficacy, usefulness and perceived need for these products in our agricultural systems.  To do this, we need your help with identifying, documenting and quantifying losses to early season pests, such as seedcorn maggot and wireworm in your corn and soybean fields.

pest in soybeanA collaborative effort between the NYS Integrated Pest Management program and Cornell Cooperative Extension field crop specialists will begin in 2020 with the goal of monitoring for and documenting losses to pests that the neonic seed treatments are intended to protect against.  Given the sporadic distribution of damage caused by seedcorn maggot and wireworm, it can be challenging to quantify losses to these pests in research plots alone.  Therefore, we need assistance from farmers, crop consultants, agribusiness associates, and crop insurance claim adjusters to report fields with damage from these pests across NY State.

Your valuable input would require nothing more than a phone call or email to your local field crops extension specialist to report the specific location of damage soon after planting, while pests are still active and can be confirmed (by V2 stage).  The extension specialist will then visit the field to confirm pest activity, and may conduct plant stand counts to estimate potential yield losses.  Location and farm identity will remain anonymous, as we are only interested in quantifying losses across NYS, not where they occur.

Claims on the value (or lack thereof) of these insecticide seed treatments in NY field crop production cannot be validated or quantified without this sort of data, and we can’t obtain this statewide data without your assistance.  Therefore, whether you grow corn for silage or grain (or even sweet corn), soybean or dry beans, conventionally or organically, we need to hear from you!  Please refer to the following list of specialists to contact in your region to report damage from seedcorn maggot or wireworm in your fields this spring:

Mike Stanyard (NWNY CCE) – mjs88@cornell.edu, 585-764-8452

Jodi Putman (NWNY CCE) – jll347@cornell.edu, 585-991-5437

Jaime Cummings (statewide, NYS IPM) – jc2246@cornell.edu, 607-255-1747

Josh Putman (SWNY CCE) – jap473@cornell.edu, 716-490-5572

Janice Degni (SCNY CCE) – jgd3@cornell.edu, 607-391-2660, x414

Ron Kuck (Cayuga Co. CCE) – rak76@cornell.edu, 315-255-1183, x242

Jeff Miller (Oneida Co. CCE) – jjm14@cornell.edu, 315-736-3394, x120

Kevin Ganoe (CNY CCE) – khg2@cornell.edu, 315-866-7920, x230

Aaron Gabriel (ENY CCE) – adg12@cornell.edu, 518-380-1496

Ken Wise (ENY, NYS IPM) – klw24@cornell.edu, 845-677-8223

Christian Malsatzki (SENY CCE) – cpm78@cornell.edu, 845-340-3990

Joe Lawrence (statewide, PRO Dairy) – jrl65@cornell.edu, 315-778-4814

Mike Hunter (NNY CCE) – meh27@cornell.edu, 315-788-8450, x266

Kitty O’Neil (NNY CCE) – kao32@cornell.edu, 315-854-1218

Elson Shields (Cornell Field Crops Entomologist) – es28@cornell.edu, 607-255-8428

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2020 Cornell Guide for Integrated Field Crop Management Now Available

2020 Field Crops Guide CoverThe Pesticide Management Education Program (PMEP) at Cornell University is pleased to announce the availability of the 2020 Cornell Guide for Integrated Field Crop Management.

Written by Cornell University specialists, this publication is designed to offer producers, seed and chemical dealers, and crop consultants practical information on growing and managing field corn, forages, small grains, and soybeans. Topics covered include nutrient management, soil health, variety selection, and common field crop pest concerns. A preview of the Field Crops Guide can be seen online at https://cropandpestguides.cce.cornell.edu.

Highlighted changes in the 2020 Cornell Field Crops Guide include:

    • Revised pesticide options for economically important field crop pests.
    • Updated corn, forage, and small grain variety trial and research data.
    • Pesticides available for stored grain management.

Cornell Crop and Pest Management Guidelines are available as a print copy, online-only access, or a package combining print and online access. The print edition of the 2020 Field Crops Guide costs $31 plus shipping. Online-only access is $31. A combination of print and online access costs $43.50 plus shipping costs for the printed book.

Cornell Guidelines can be obtained through your local Cornell Cooperative Extension office or from the Cornell Store at Cornell University. To order from the Cornell Store, call (844) 688-7620 or order online at https://www.cornellstore.com/books/cornell-cooperative-ext-pmep-guidelines.

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Potato Leafhopper in Alfalfa

Ken Wise and Jaime Cummings NYS IPM

Across the state, there are many reports of potato leafhopper (PLH) approaching threshold in alfalfa. It is important protect your alfalfa quality by knowing what to do and how to determine if a field has a problem.

This insect pest does not over-winter in the Northeast. Adult PLHs migrate on weather from south and south-west part of the county each year.  This year we have had a lot of storms and weather fronts. Many field consultants are reporting finding many numerous adult PLHs in alfalfa fields.

This lime green, slender 1/8 inch long insect can move from plant to plant laying 2-3 eggs per day. Bright yellow-green nymphs hatch from the eggs in search of plant juices.

Potato Leafhopper Adult
Potato Leafhopper Adult
Potato Leafhopper Nymph
Potato Leafhopper Nymph


Adults alone seldom reach threshold (and they already have this year), but the combination of the nymphs and the adult can really cause significant damage to the forage. Both the nymphs and adults have piercing-sucking moth parts. As they suck the sugary phloem juices from the plant, they replace it with their toxic saliva.

Large infestations of potato leafhopper in alfalfa can reduce the plant crude protein by 5% and yield by a ½ ton per acre per cutting. If you see V-shaped yellowing on the tips of the leaves you have a good chance that potato leafhopper has been in your alfalfa. This weakens the plant and it will have slower re-growth after harvest and increased chance of winter kill.

V-Shaped Yellowing by Potato Leafhopper
V-Shaped Yellowing
Field Yellowing from Potato Leafhopper
Field Yellowing from Potato Leafhopper

It is TIME TO SCOUT YOUR FIELDS!  Use a 15-inch diameter sweep net to determine if a field is at threshold.

You will want to scout from now until late August. Use the potato leafhopper sequential sampling plan to determine if an infestation requires management or not. The first thing to do is determine the height of your alfalfa. Smaller plants are more vulnerable to potato leafhopper; thus there are different action thresholds for different heights of alfalfa. The second thing you will need to know is how to sample for potato leafhopper.

A sample consists of a set of 10 sweeps of the net. A sweep is one pass in front of you as you walk through the alfalfa. The return swing is counted as another sweep.

Since sequential sampling reduces the number of samples that taken, it reduces the time in each field and tells you whether to treat (management action) or not treat (no management action). Sequential sampling is particularly helpful in minimizing time required to make a management decision in situations where PLH populations are very high or very low. Use the following chart to determine potato leafhopper infestation levels.

Sequential Sampling Card for Potato LeafhopperWrite down the number of potato leafhoppers for each sample taken on the card. Add each sample to the next, keeping a running total of potato leafhoppers. You will need to take at least 3 samples using the sequential sampling method. On the sequential sampling card “N” is defined as no treatment (no management) needed at this time and “T” is defined as treatment (management) needed within in a week. If the sample is smaller than the “N” number stop and scout 7 days later. If the number of leafhoppers is larger than the “T” number then management action needs to be taken within a week. If the number of potato leafhoppers fall between “N” and “T” then continue and take the next sample till a decision can be determined. A guide with a printable version of the sequential sampling chart can be found at: http://www.nysipm.cornell.edu/publications/plh.pdf

Now you need to know what to do if an infestation reaches a management action level. The good news is that you have three good options for controlling an infestation of potato leafhoppers in New York alfalfa.

Option 1: Early Harvest

You can harvest the alfalfa early to control PLH if the field is within a week to ten days of a scheduled harvest. By harvesting the alfalfa early, you’ll prevent potato leafhopper from reaching infestation levels that can cause yield and quality loss to the forage. Make sure that the whole field is harvested at the same time. If a field is not clean harvested then the alfalfa that has not been cut will serve as a refuge for PLH that can re-infest; thus severely damaging alfalfa re-growth.

Option 2: Use an Insecticide

To protect yield and health of new seedings and established alfalfa, insecticide control may be warranted when an infested field is not within a week of harvest. For selection of an insecticide, consult the current issue of Cornell Guide for Integrated Field Crop Management. Remember to read the label and be aware of blooms, bees and the days until harvest restrictions.

Option 3: Plant Potato Leafhopper Resistant Alfalfa

A third option for control is planting PLH-resistant alfalfa. Obviously, it is a little late for this season’s crop but something to consider for future seedings. Research has shown that potato leafhopper resistant alfalfa is consistently higher in quality than susceptible alfalfa varieties with or without potato leafhopper pressure. PLH-resistant variety yields are comparable and generally better than susceptible varieties when PLH are present. A bonus benefit is that currently available alfalfa varieties with PLH resistance have come down in price over the past several years.

PLH DAMAGED ALFALFA NOTE: If you have standing alfalfa with potato leafhopper yellowing across the field, it is best to clip off the alfalfa instead of treating it, and then monitor the regrowth. The reason is that the quality of the PLH damaged forage is going to be poor, at best, and you will get a better quality forage if you protect the regrowth.

For more information check our online IPM video: Time to Scout for Potato Leafhopper in Alfalfa


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NNYADP Research Prompts Request for 23 Billion Biocontrol Nematodes by Farmers in Southwest; Protocol Expanding in NY

Cornell University Entomologist Elson Shields, right, talks with farmer Gary Frost as cups filled with biocontrol nematodes from New York State await application on Frost's farm in Dalhart, TX.
Cornell University Entomologist Elson Shields, right, talks with farmer Gary Frost as cups filled with biocontrol nematodes from New York State await application on Frost’s farm in Dalhart, TX. Photo courtesy of Patrick Porter

In May, Cornell University entomologist Elson Shields, Ph.D., and Research Support Specialist Antonio Testa transport 23 billion native New York nematodes to farms in Texas and New Mexico for field application against Western corn rootworm. Shields and Testa, who pioneered the use of biocontrol nematodes as a crop pest management protocol, built a generator-powered system to maintain a temperature of 70 degrees Fahrenheit to protect the nematodes under the cap of a pickup truck.

Researchers, crop consultants, and farmers in several U.S. states are now testing the nematode application, initially developed to beat alfalfa snout beetle back, against an increasing number of agricultural crop pests.

With long-term funding from the farmer-driven Northern New York Agricultural Development Program, Shields and Testa created the science and the nematode-rearing procotol behind the use of native nematodes for controlling alfalfa snout beetle, the most highly destructive crop pest of the alfalfa crops so critical to the regional dairy industry.

Over time, the biocontrol application has been field-tested and increasingly proven its value as a biocontrol for managing pests in corn, berries, potatoes, and potentially other crops.

“The science built and proven in Northern New York over the course of more than 30 years for using the native nematodes as a crop pest biocontrol has steadily expanded to help farmers across New York State and other states and to address pest issues in multiple crops,” said Shields. “The expansion of this cost-effective, easy-to-apply management practice would not be possible were it not for the long-term commitment the farmers of Northern New York needed to develop the science to support a solution for snout beetle.”

With local funding, Texas Agri-Life Extension entomologists and private ag consultants are jointly conducting large farm trials testing the NY nematodes as a biocontrol to manage corn rootworm in Dalhart, TX, and growers have completely funded trials in Riodoso, NM. Applications have been made to more than 900 acres using both ground application and through a center pivot irrigation system.

Having learned of the concept using persistent biocontrol nematodes while working in West Texas, a newly-hired Extension entmologist with Auburn University in Alabama recently contacted Shields about trying the biocontrol nematodes to manage billbugs, a type of beetle that impacts lawn, sod and grass crops.

In 2019 with a new grant from the Northern New York Agricultural Development Program, Cornell University Cooperative Extension Field Crops Specialist Mike Hunter is evaluating the application of the biocontrol nematodes in manure as a way to incorporate the pest management practice into an existing farm task. The research prompted the creation of a new business enterprise now raising the biocontrol nematodes locally for application by farmers and custom spraying services in the Northern New York region.

The number of acres treated with biocontrol nematodes in Northern New York has steadily grown to protect the alfalfa crops on more than 20,000 acres. Shields estimates that recent dairy prices have curbed applications expected to cover more than 100,000 acres with the biocontrol nematodes by this time.

The Shields Lab at Cornell University has also received a Northeast Sustainable Agriculture Research and Education grant to expand biocontrol nematode-corn rootworm applications throughout New York State and to assist similar start-up research in Vermont and Pennsylvania.

Funding for the Northern New York Agricultural Development Program is supported by the New York State Legislature and administered by the New York State Department of Agriculture and Markets.

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