Managing Corn Rootworm in NY to delay Bt resistance (& save seed costs)

Elson Shields, Entomology, Cornell University

Across the US and within NY, corn rootworm (CRW) is developing resistance to the Bt-RW traits in our GE corn varieties, causing increased root damage and decreasing yields.  Yield losses from CRW root feeding can surpass 10% without any above ground symptoms, making this type of losses difficult to detect.  In addition, corn grown for silage is more sensitive to yield losses from CRW feeding than corn grown for grain.  As CRW resistance increases to Bt-RW, the damage becomes more apparent and easier to detect, but losses have been occurring in the field in prior years, going undetected.  Increased damage has been reported in NY for all of the Bt-RW traits regardless of company.

Important points about CRW biology:  There are two important points about CRW biology which need to be remembered when managing this pest and reducing its potential for developing resistance to any of our management tools.  1)  In NY, all eggs are laid in existing corn fields during August, and 2) if the newly hatch CRW larvae in the spring do not find a corn root, they die.  Since CRW eggs are laid in existing corn fields in August of prior year, crop rotation is our best resistance management tool.  Since the majority of the corn grown in NY is in rotation with alfalfa for our dairy farms, NY trails the rest of the nation in the development of CRW resistance to Bt-RW.

For our dairy farmers, that grow corn in rotation with alfalfa, corn is typically grown in a field for 3-5 years.  The longer corn is grown continuously in a field, the higher risk the field has for economically damaging CRW root feeding and yield losses.  After rotating out of a non-corn crop, first year corn does not need any CRW management (or expensive Bt-RW trait costs).  A non-Bt-RW corn variety should be planted with a seed corn maggot/wireworm effective seed treatment.  This choice in year 1 saves $15-$20 per acre in seed costs.  In year 2, the risk of CRW loss increases to 25-30% in NY.  To offset this risk, a farmer has several options.   Many farmers will assume the risk and plant a non-Bt-RW corn variety without any additional protection such as a soil insecticide.  A second option in year 2 is to use either a 50% rate of soil insecticide (if insecticide boxes are available), high rate of neonic seed treatment or an insecticide added to the liquid popup fertilizer.  The CRW pressure in year 2 is not high enough to recommend the use of Bt-RW in most cases and the option of an insecticide is often a less expensive route to reduce production costs.   The deployment of different modes of toxicity in year 2 from Bt-RW significantly reduces the selection for Bt-RW resistance by CRW.  In continuous corn years 3-5, the risk of economic loss from CRW is high enough to merit the use of Bt-RW corn varieties.  A second option in years 3-5 of continuous corn is the use of a full rate of soil insecticide, if insecticide boxes are available.  Adding insecticide to the popup fertilizer during years 3-5 is not recommended due to unreliable efficacy with the higher CRW populations and increased risk for economic damage.

Strategy 2 for our dairy farmers:  Incorporating biocontrol nematodes into their rotation and crop production.   

By using the biocontrol nematode technology developed to combat alfalfa snout beetle in NNY, our dairy farmers can reduce their corn seed costs by eliminating the purchase of the Bt-RW traits in their corn varieties.  A single inoculation of each field with native persistent NY biocontrol nematodes provides protection from corn rootworm larval feeding by attacking these insects before they damage the corn roots.  NY research data indicates a single soil inoculation ($50-$60/acre) establishes these NY adapted biocontrol nematodes in the soil profile for many years, where they attack a wide range of pest soil insects across a wide variety of crops.  During the corn years, these biocontrol nematodes attack rootworm larvae and during the alfalfa years, attack wireworms, white grubs, clover root curculio feeding on the alfalfa and grass in the field.

If the biocontrol nematodes are inoculated into the field during the alfalfa portion of the crop rotation, the farmer can use corn varieties without Bt-RW for the entire corn rotation.  Biocontrol nematodes take until the second growing season after application to become fully established in the soil profile and when applied to the alfalfa crop, become fully established before corn is planted.  If the field is inoculated with biocontrol nematodes during the first year of the corn rotation, the corn variety planted in year 1 can be without the Bt-RW trait because rootworm is never a problem in 1st year corn in NY.  By the second year, the biocontrol nematodes are fully established and corn varieties can be planted without Bt-RW for the remaining years of the corn portion of the rotation.

However, if the corn field is inoculated with biocontrol nematodes during the 2nd-4th year when rootworm damage risk is higher, the corn variety planted during the year of inoculation needs to have the Bt-RW trait to provide some additional protection while the biocontrol nematodes become fully established in the field.  If the cost of establishing biocontrol nematodes in a field is a one-time cost of $50-60/acre and the Bt-RW trait adds $20/acre/year to the seed costs, the breakeven point for the nematode application is year 3 when the Bt-RW trait is not purchased or used.  In the years beyond 3-years after application, the seed cost savings will continue to be the cost of the Bt-RW which is an unnecessary expense.

For our cash grain farmers, an annual rotation of corn and a non-host crop like soybeans completely eliminates the need for any CRW management tools.  During the corn years, non Bt-RW corn varieties can be safely planted without risk of losses from CRW.  The elimination of the Bt-RW trait in the corn planted reduces the seed cost $15-$20 per acre and the use of a Bt-RW trait is completely unnecessary.  However, a seed treatment for seed corn maggot to protect plant emergence is recommended due to our typically wet cold soils.  The enhanced adoption of cover crops to protect our soil from erosion and any history of animal manure application significantly increases the risk of plant stand losses from seed corn maggot.

Long-term continuous corn fields:  The culture of corn continuously in the same field for multiple years using only Bt-RW to control CRW places tremendous selection pressure for the insect to develop resistance to the Bt-RW toxins.  This widespread practice across the corn belt has resulted in the documented CRW resistance to all Bt-RW traits and the insect is causing economic losses for farmers adopting these continuous corn practices.  Closer to home, Bt-RW failures have been reported in Central NY corn fields, multiple corn growing areas of Ontario, Canada and to the south in Pennsylvania.  With no new technology against CRW available for the next few years, these growers have a real challenge on their hands to minimize losses from this adaptable insect, if these farmers continue with long-term continuous corn production without breaking the CRW cycle with crop rotation.  Farmers with fields producing corn continuously for multiple years need to seriously consider working a crop rotation into their farming practices.  There are well documented agronomic yield advantages/responses from crop rotation over continuous corn, even without considering the reduction in CRW root feeding damage.

However, if farmers insist on growing continuous corn in field without interruption, there are several issues to consider.  The continued use of Bt-RW accelerates CRW resistance and the single field failure becomes the source of highly resistant beetles moving into neighboring fields, causing significant yield losses even in neighboring fields where farmers are utilizing crop rotation to minimize CRW-Bt-RW resistance development and yield losses.  The farmer growing continuous corn and producing highly resistant beetles becomes “a neighborhood social problem” for his neighbors.  Some farmers add a soil insecticide over the top of the Bt-RW trait, think this is a solution to the resistance issue.  While the corn stands better with less damage at the plant base, selection for CRW Bt-RW resistance continues to accelerate within the root system in areas outside of the soil insecticide treated zone.

The addition of biocontrol nematodes to the continuous corn culture is a way of introducing an independent mortality factor to help the Bt-RW trait control rootworm larval populations.  However in these high CRW pressure systems, biocontrol nematodes should not be used alone.  CRW has developed resistance to every other management strategy used to manage its damage, biocontrol nematodes used alone will also select for CRW resistance.  If farmers are interested in incorporating biocontrol nematodes into their continuous corn production, farmers should continue to use varieties with the Bt-RW trait to continue to kill the susceptible CRW larvae or match the use of biocontrol nematodes with a full rate of soil insecticide.

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NYS IPM Field Corn Pheromone Trapping Networks Helps Growers Avoid Potential Damage from Black Cutworm, True Armyworm and Western Bean Cutworm

Ken Wise and Jaime Cummings: NYS IPM Program

Black cutworm, true armyworm and western bean cutworm are all migratory pests of field corn. These three pests are all species of moths. Black cutworm and true armyworm are early season pests that migrate on weather fronts from the south and southwest of New York each year. Black cutworm will feed on small corn seedlings up to the sixth leaf stage. True armyworm can occur at very high populations and can destroy whole fields of corn. Western bean cutworm is a mid to late season moth species of field corn. The larvae will enter the ear of corn and can cause significant damage. To help combat these insect pests, the NYS IPM with funding from the NYS Corn and Soybean Association, developed a field corn pheromone trapping network.

The field corn pheromone trapping network is a group of extension educators, crop consultants and farmers who set up insect pheromone traps next to corn fields and monitor for the flight and abundance of the three pests. We started the network in 2010 monitoring a new invasive species, the western bean cutworm, and in the last two years we have included black cutworm and true armyworm. The network includes 24 people who monitor and report the number of moths they catch each week. In 2020, we had 20 black cutworm, 20 true armyworm and 63 western bean cutworm traps setup statewide. The purpose of the network is to identify areas of the state that have a high number of moth captures for the particular pest and to then alert growers to the potential damage that might occur. This helps the growers and crop consultants to start scouting fields for the pests. For black cutworm and true armyworm, we define an intense catch as 15 moths caught in a week. At this point, we can predict when larvae will be in the field by using specific degree day models. This is then communicated to the grower via field crops extension specialists across the state and publications like the Weekly NYS IPM Field Crops Pest Report, local extension crop alerts, and social media.

Western bean cutworm (WBC) monitoring occurs in the same manner as black cutworm and true armyworm. Once a trap reaches 100 moths caught in a week at a specific location, it is a good indication that the cornfields surrounding the trap should be monitored for WBC. WBC female moths almost exclusively only lays eggs on pre-tassel corn. The 100 moths caught per trap in a local area will prompt WBC alerts to growers in the local area. Northern NY is the epicenter of WBC flights. Some traps in Northern NY catch more than 1000 per week/trap, and in some cases 2000 moths.  Because of this network, we can help growers determine the peak flight of WBC and scout fields accordingly each year.

A second benefit of the monitoring is that we can collect data and follow the expansion of WBC and the flights of black cutworm and true armyworm from year to year. With two years of data for black cutworm and true armyworm, the data base is starting to grow. With WBC, we have 11 years of data outlining the expansion and peak flights of the moth.

There were 20 traps placed next to corn fields to monitor BCW and TAW in 2020. These 40 traps in total were monitored by 15 extension educators, crop consultants and growers from April through mid-June. We had some significant flights of BCW and TAW this year. The following maps illustrate the trap catch intensities from green to yellow to red:

map with dots indicating counts
Figure 1. NYS Black Cutworm Trap Counts for 2020
map of NYS and true armyworm counts
Figure 2. NYS True Armyworm Trap Counts for 2020

The flight of BCW and TAW started in April and extended to mid-June. There were reports of high levels of these pests in corn. In some cases, due to this network, growers were able to avoid damage by scouting and determining if BCW and TAW were above an economic threshold, to make treatment decisions.  Much of western NY and the mid- Hudson Valley had significant catches of black cutworm. There were significant catches of TAW in western and central NY.

graph of counts
Figure 3. Flight of True armyworm and black cutworm in NY 2020
Table of averages
Table 1. Average number of moths caught per trap

For WBC, there were 63 traps next to corn fields across NYS. We had 24 extension educators, crop consultants and growers monitoring WBC weekly from late June through late August. There were significant flights of moths, as illustrated in Figure 4, in Northern NY. The rest of the state had relatively low levels of WBC flights in 2020.  The major goal of this project during the season is to alert growers to the peak flight of the moths. At this time, the moths will lay eggs on pre-tassel corn. By knowing when peak flight is, we can alert growers to scout their corn fields for egg masses and small larvae. If they are over the economic threshold, then growers can treat a field before the larvae enter the ear of corn, because once the larvae enter the ear of corn, an insecticide application will have no effect on control.

map of NYS with dots indicating counts
Figure 4. NYS Western Bean Cutworm Count Totals 2020
bar graph showing peak flights from 2010 to 2020
Figure 5. Peak Flight of WBC by Year

The overall peak flight for WBC in 2020 was the earliest we have had since we started monitoring in 2010. When you break out the data and look at Northern NY compared the rest of the state, it shows the peak flight in NNY was the week of July 25th, but in the rest of the state it was a week earlier.  The average number of moths caught per trap in 2020 was down a little from 2017 and 2019, but about the same as 2018.

graph showing how much higher the counts in northern NY are
Figure 6. Peak flight in Northern NY vs the rest of the state
graph of moths caught from 2011 to 2020
Figure 7. Average number of moths caught per trap for WBC each year
graph of moths caught in NNY
Figure 8. Average number of moths caught per trap in Northern NY vs the Rest of NY

If you look at the data from 2017 to 2020, the average trap counts were much higher in Northern NY compared to the rest of the state. The highest risk of damage by WBC to grain corn is in northern NY.

As part of the project, we survey those who were involved regarding the benefits and impacts of the field corn pheromone trapping network. Of those who responded to the survey, 93% stated that monitoring for black cutworm, true armyworm and western bean cutworm were beneficial to them or their growers.

pie chart
Figure 9. The benefit of the field corn pheromone trapping network.

Most survey respondents also indicated they used the information from the trapping network to alert their growers to the potential damage from these insect pests. Many of these use their local weekly newsletter, but many made personal contacts with growers and helped determine if fields were at an economic threshold.

pie chart
Figure 10. Alerting growers to the potential damage from pests.

Multiyear monitoring, such as this corn pest network, provide invaluable data on the trends of infestations so that NY farmers can proactively scout for these pests and make appropriate management decisions.  We hope to continue these surveys in future years, and potentially expand the BCW and TAW networks.  We thank all collaborators for their time and efforts, and NYCSGA for the financial support to continue this project.

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Are Persistent Biocontrol Nematodes (Entomopathogenic) an economic benefit for your NY farm?

Elson Shields and Tony Testa, Department of Entomology, Cornell University

What are Biocontrol Nematodes?

Biocontrol nematodes are microscopic round worms in the soil which only attack insects in the soil or on the soil surface.  Biocontrol nematodes are different from the plant parasitic nematodes which attack crops.  The biocontrol nematodes discussed here are native to our Northern New York (NNY) soil where they were original collected.  The nematode insect infective stage (called the Infective Juvenile or IJ) moves about in the soil in search of insect hosts, finding the insect using CO2 gradients and other chemical attractants.  When an insect host is located, the IJ enters the insect through a breathing opening called a spiracle and enters the insect body cavity.  Once inside, the nematode releases a bacteria which kills the insect.  The nematodes then molt to adults and produce offspring on the nutrition provided by the dead insect.  When the insect resources are consumed, a new set of IJs are released into the soil to search for additional insect hosts.  An average sized insect larvae will produce between 100,000 and 200,000 new IJs.

What do these biocontrol nematodes attack?

This entire technology was developed to reduce snout beetle (ASB) populations to sub-economic levels in NNY.  ASB is costly to the dairy farmer, commonly killing alfalfa stands in a single year.  The economic costs of ASB on dairy farmers is very high and often hidden.  Dairy farms are impacted by the high cost of replacing alfalfa fields and the high cost of purchasing replacement feed to replace the loss of alfalfa production.  Estimates of these dual costs exceed $30,000 per 100 cows on the farm annually.  To date, more than 150 NNY farms have applied biocontrol nematodes to >25,000 acres to successfully reduce snout beetle to a sub-economic level and increase stand life back to 3-5 years.

Corn Rootworm:  During the research developing the use of native persistent biocontrol nematodes to reduce ASB populations in NNY to sub-economic levels, it was discovered that biocontrol nematodes applied in alfalfa for snout beetle control also carryover to attack corn rootworm when the field is rotated to corn.  Not only are the biocontrol nematodes completely compatible with all of the Bt-RW traits, killing the Bt toxin survivors, but in NY, the biocontrol nematodes appear to be capable of being used alone if the farmer chooses to grow non-Bt-RW traited corn.  Research has shown that after 4 years of corn, the populations of biocontrol nematodes in the field are high enough to attack alfalfa soil insects when the field is rotated back to alfalfa.

Wireworm and White grubs:  Since NY alfalfa culture usually incorporates grass into the mix, NNY fields usually have a population of wireworms and native white grubs in the field when the field is rotated to corn.  Often, these insects then cause stand problems in 1st year corn.  If the field has been inoculated with biocontrol nematodes for control of either snout beetle or rootworm, the biocontrol nematodes also attack these insects and reduce their impact on seedling corn when rotated to corn.

Seed corn maggot:  With our corn and soybean insecticide seed treatments under attack, the questions arises whether biocontrol nematodes present in the soil will be effective against seed corn maggot under NY spring conditions.  Seed corn maggot is killed by biocontrol nematodes in the laboratory, but the question is whether the biocontrol nematodes can work fast enough in the field under the cool spring soil temperatures.

Does the soil type influence the species of biocontrol nematode applied?

NY research data indicates a mix of biocontrol nematode species gives better control of soil insects than a single species alone.  The reason for these results is each nematode species has a preferred section of the soil profile where it is most effective.  For example, Steinernema carpocapsae prefers the top 2-3” of the soil profile and dominates this region.  If S. carpocapsae is the only nematode used, insect larvae below the 2” level escape attack.  The addition of a second nematode species which prefers the low portions of the soil profile compliments the presence of S. carpocapsae and gives more complete control of soil insects throughout the plant root zone.  In sandier soils, the top 2” often become too dry for a biocontrol nematode to move and attack insect larvae.  In these soils, a nematode species mix which include S. carpocapsae would be ineffective and requires a different mix of nematode species.

Our recommendations for biocontrol nematode species mixes for soil types:

Clay loam – silt loam soils:  S. carpocapsae + S. feltiae

Sandy loams – sand soils:  S. feltiae + Heterorhabditis bacteriophora.

What are the differences between the entomopathogenic (biocontrol) nematodes purchased on the web from the Persistent NY strains mentioned here?

Biocontrol nematodes purchased from commercial sources have lost the ability to persist in the soil after application for a significant length of time.  Many commercial strains persist in the soil for only 7-30 days and require application timing to be closely match with the presence of their target host, requiring an annual reapplication.  In contrast, the NY persistent strains of Biocontrol Nematodes are carefully cultured to maintain their evolutionary ability to persist across hostile conditions such as the lack of available hosts and temperature extremes (dry soil conditions, winter).  Additionally, NY persistent strains are re-isolated from the field every two years so the nematode cultures do not become “Lab strains”, but remain adapted for NY agricultural soil conditions.  New York persistent strains are applied once and persist in the field for many years following application.  Not surprising because they were isolated from NY soils where they have evolved for a few million years.  If the NY persistent strains are cultured carelessly, they also quickly lose their ability to persist and are no better than the commercial strains purchased off the web.

How are biocontrol nematodes applied?

There are two major ways to apply biocontrol nematodes to NY fields.

Commercial Pesticide Sprayer:  Thousands of acres have been inoculated using slightly modified pesticide sprayers of all sizes from 30’ booms to 100+’ booms.  To use these sprayers, the following guidelines need to be followed.

    1. A good washing of the sprayer (similar to changing pesticides)
    2. All screens and filters removed (nematodes cannot pass through them
    3. Nozzle change to a stream type nozzle to shoot a concentrated stream of water to the soil surface through any vegetation.
    4. 50 gpa minimum
    5. Application in the evening or under cloudy/rainy conditions (nematodes are sensitive to UV)

Liquid Dairy Manure:  This method was recently developed and offers some advantages over using a pesticide sprayer.  The biggest limitation is the time between adding the nematodes to the liquid manure and field application.  After adding the nematodes to the manure, the manure needs to be spread in the field within 20-30 minutes.  Longer intervals results in the nematodes dying from the lack of oxygen.

The advantages of using liquid dairy manure as the carrier are 1)  no extra trips over the field, 2)  can be applied any time of the day and 3)  no extra costs.

Application timing:

Biocontrol nematodes which are persistent, can be applied anytime during the growing season when soil temperatures are above 50 F.  Ideally, nematodes should be applied when there are host in the soil so they can immediately go to work and reproduce.  However, the NY persistent strains have the ability to sit and wait for months before needing to attack hosts and reproduce.  We request that no nematode applications be made after September 15th due to cooling soil temperatures and limited time to find hosts before winter.  Applications are made to the soil surface under conditions of low UV exposure (late in the day, rainy/overcast days, in cover crops where there is adequate ground shading).  Field tillage has no impact on biocontrol nematodes.  In addition, if nematodes are applied before field tillage, the movement of soil during tillage helps the nematodes redistribute throughout the field and help them fill in the gaps which may occur during application.

Where can I get Biocontrol Nematodes which are adapted to NY and will persist across growing seasons?

Currently, there are two sources to purchase biocontrol nematodes adapted to NY growing conditions with their persistent genes intact to persist across growing seasons (and winter) in NY.

    • Mary DeBeer, Moira, NY.  cell:  (518) 812-8565  email:  md12957@aol.com
    • Shields’ Lab, Cornell University: Tony Testa  email:  at28@cornell.edu  cell: (607) 591-1493
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NYS IPM Field Corn Pheromone Trapping Network for 2020 Caught Moths in Mid-April!

Ken Wise and Jaime Cummings – NYS IPM Program

The NYS IPM Field Corn Pheromone Trapping Network has started trapping black cutworm (BCW) Agrotis ipsilon and true armyworm (TAW) Mythimna unipuncta moth flights in NYS. While it seems like it might be early, we have caught BCW and TAW moths this week in Western, NY in pheromone bucket traps. These moths migrate north on weather fronts from the southern US every year. Both BCW and TAW prefer feeding on grasses, such as grassy weeds, hay fields, small grains and corn.

Even though the number of moths caught this week were low, it indicates that they have arrived. From this point forward, we can set the “Biofix Date”. The biofix date is the point where we start to calculate the number of BCW and TAM degree-days. We can predict when the eggs that were laid by moths will hatch. Degree-days are calculated by taking the high and low temperature each day and averaging them from the biofix date. Next, subtract the base temperature of 50 degrees Fahrenheit, and this will give you the daily degree-days. Each day, add the number of BCW degree days and this will give you a total. When this reaches 90 BCW degree-days and 113 TAW degree-days, the eggs will start to hatch.

High Temperature + Low Temperature/2 – 500 F = daily BCW degree days

The easy way to calculate this is to use the NEWA Degree Day Calculator. This will calculate the degree-days from a weather station near your farm. Below is the information on degree-days for the lifecycle of BCW and TAW.

Black Cutworm Degree Days (Base 500 F)

Degree Days               Stage                           Feeding Activity

0                                  Moth Capture              Egg Laying

90                                Eggs Hatch

91-311 1st to               3rd Instar                     Leaf Feeding

312-364                       4th Instar                     Cutting Begins

365-430                       5th Instar                     Cutting Begins

431-640                       6th Instar                     Cutting Slows

641-989                       Pupa                            No feeding

Source: University of Minnesota Insect Pest of Corn-Stand Reducers Black Cutworm

True Armyworm Degree Days (Base 500 F)

Degree Days               Stage                           Feeding Activity

0                                  Moth Capture              Egg Laying

113                              Eggs Hatch

612                              Larval stages               Leaf Feeding

909                              Pupa                            No feeding

Source: Scouting for True Armyworms Is Highly Recommended in Small Grains and Early Corn-University of Kentucky

A large number of moths in a trap does not necessarily mean there is going to be damage in your corn. It will depends on where the moths lay eggs. If a trap near your farm has a large number of moths, it would suggest it is time to scout for larvae and signs of feeding damage.

A good time to start scouting is when you take plant population counts. BCW damage is easy to identify. The larvae will cut the plant near the base at the soil surface, while TAW will feed from the edge of the leaf to the mid rib.

black cutworm armyworm control tableBCW and TAW larvae are primarily nocturnal or night feeders. Normally, you will not see them during the day. BCW larvae are ½ inch to 2 inches. They appear as greasy gray with darker raised spots on each segment. They normally hide in the soil near the base of the corn or under residue that might be on the surface.

Black Cutworm
Photo by Ken Wise, NYS IPM

TAW larvae range from ½ to 1.5 inches long. They have orange and white strips running along the side. They also have a white strip running down the back. TAW will hide under surface residue, in the whorl of the plant or in cracks in the soil.

True Armyworm
Photo by Keith Waldron, NYS IPM

If you are at threshold, and the larvae are still small, try to treat only the infected corn and a 20 to 40 foot border around the area. When the larvae are large (1.25 inches +) they are harder to kill with an insecticide, and they will pupate soon. When pupating, they will stop feeding.

One of the issues with BCW and TAW is that there can be multiple flights on different weather fronts throughout the spring. This can cause multiple infestations with different sizes of larvae in a field. Still follow the economic threshold, and manage if needed.

Our pheromone-trapping network has 25 traps of each BCW and TAW placed in 19 counties across the state. The counts and degree-days for many locations across NY will be published weekly starting later in April in the NYS IPM Field Crops Pest Report .

References:

University of Missouri-True Armyworm

University of Minnesota Insect Pest of Corn-Stand Reducers Black Cutworm

Cornell University Field Crop-Armyworm

Purdue University-Armyworm

Purdue University-Black Cutworm

Cornell University Guide for Integrated Field Crop Management

Scouting for True Armyworms Is Highly Recommended in Small Grains and Early Corn-University of Kentucky

This work is funded by the NYS Corn and Soybean Growers Association.
NY Corn & Soybean Growers Association logo

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