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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What’s Cropping Up? Volume 30 No. 2 – March/April 2020 Now Available!

What’s Cropping Up? Volume 30 No. 1 – January/February 2020 Now Available!

Soybean Cooperative Agricultural Pest Survey: Vigilance against Potentially Invasive Species

Jaime Cummings and Ken Wise (NYS Integrated Pest Management Program), Mike Hunter, Mike Stanyard, Aaron Gabriel and Kevin Ganoe (Cornell Cooperative Extension), and Michael Dorgan (NYSDAM)

Cooperative Agriculture Pest Survey Header
 Image courtesy of Purdue University CAPS website

Annual funding in the Plant Protection Act 7721 supports the Cooperative Agricultural Pest Survey (CAPS) pest detection program, led by the USDA Animal and Plant Health Inspection Service (APHIS), to safeguard against introductions of potentially harmful plant pests and diseases.  These surveys ensure the early detection of potentially invasive species that could negatively impact U.S. agriculture and/or environmental resources.  The NYS Department of Agriculture and Markets (NYSDAM) works with APHIS to prioritize the potentially invasive species to monitor in economically important commodities in NY each year.  In 2019, NYSDAM partnered with the NYS Integrated Pest Management (IPM) program to coordinate a soybean CAPS survey to monitor for two potentially invasive moth species, as well as to expand monitoring of the soybean cyst nematode across New York soybean production areas.

The overarching goal of the CAPS program is to monitor for species that shouldn’t be here, and to confirm that they still aren’t in NY or even the U.S.  These surveys are often the result of cooperation among state and federal employees, such as APHIS pest inspectors, NYSDAM inspectors and extension specialists.  This ‘boots on the ground’ approach allows for broad coverage of the surveys across the state involving many individuals with agricultural and pest identification expertise.

Larva and moth
Figure 1. Golden twin spot moth and looper larva. (photos by S. Hatch and P. Hampson, Bugwood.org)

For the 219 soybean CAPS survey, two moth species that are already problematic elsewhere in the world, but not known to exist in the U.S. were selected.  The Golden Twin Spot moth (Chrysodeixis chalcites), which currently causes yield losses in Africa, Europe, the Middle East and Canada, has a larval stage known as a ‘looper’ which can cause significant damage to soybeans, tomato, cotton, tobacco, beans and potatoes (Fig. 1).  Feeding by the loopers can result in defoliation, and they can also cause foliar damage due to rolling leaves with webbing for nests.  The Silver Y moth (Autographa gamma), which is already a concern in many countries in Asia, Europe and Africa, also has a caterpillar larval state that can cause significant damage to soybeans and many other agronomically important crops, including beets, cabbage, hemp, peppers, sunflower, tomato, potato, wheat, corn and wheat (and many more) (Fig. 2).  These caterpillars also defoliate and harm leaves through rolling and webbing.  Given how potentially damaging an introduction of these pests could be to U.S. agriculture, it’s important that we are vigilant in our efforts to monitor for them and ensure they aren’t in NY.

Silver Y moth and larva
Figure 2. Silver Y moth and caterpillar larva. (photos by P. Mazzei and J. Brambila, Bugwood.org)

In addition to monitoring for these two moth species, we also prioritized a pest that has very high potential to affect soybean yields in NY, and one that has thus far only been confirmed in one field in NYS.  The soybean cyst nematode (SCN) is considered the number one pest of soybeans nationally and globally, causing an estimated 109 million bushels of yield loss in the U.S. in 2017.  Extensive collaborative sampling for this pest from 2014-2017, supported by the NY Corn and Soybean Growers Association and Northern NY Agricultural Development Program, was coordinated by Cornell University and Cornell Cooperative Extension programs.  Over the four years of the SCN survey, numerous fields in 17 counties were sampled, and one field in Cayuga County was identified as positive for SCN in 2016, albeit at very low levels (Fig. 3).  Though it’s promising that SCN wasn’t identified widely across NY, we are fairly confident that it is very likely in many more than just one field in one county.  Given the potential impact this pest could have on NY soybean (and dry bean) production, we decided to include this pest in the 2019 CAPS survey.

Soybean Cyst Nematode
Figure 3. Soybean cyst nematode survey efforts in 17 counties in NY from 2014-2017, with one positive ID in Cayuga County in 2016, and information from the SCN Coalition on why you should test for SCN.

Six collaborators (Jaime Cummings and Ken Wise of NYS IPM, and Mike Stanyard, Mike Hunter, Aaron Gabriel and Kevin Ganoe of CCE) spent part of their typical summer soybean scouting efforts from western, to central, to eastern and northern New York setting up and checking pheromone traps intended to monitor for the Golden Twin Spot moth and Silver Y moth (Fig. 4).  They communicated the importance of these surveys to cooperating farmers who agreed to host these traps in 25 fields across the state.  Any suspicious moths caught in the traps are submitted to the Cornell Insect Diagnostic Clinic for thorough identification.  Thus far, we have not caught any Silver Y or Golden Twin Spot moths.  And that’s good news!  As the growing season winds down, we will collect soil samples from the same 25 fields for SCN testing at the SCN Diagnostics laboratory.

CAPS survey distribution
Figure 4. Distribution of the 2019 soybean CAPS survey.

A funding proposal to continue this work in 2020 has been submitted.  If accepted, it may also be expanded to include a corn CAPS survey for other potentially invasive pests with additional locations in southwest and central NY.  For more information on the national CAPS program, please visit their website.  For additional information on the soybean cyst nematode, please visit the SCN Coalition website, and check out these resources on SCN efforts in NY:  Soybean Cyst Nematode Now Confirmed in NY, Sudden Death Syndrome and Soybean Cyst Nematode in Soybeans, Fall is the Time to Test for Soybean Cyst Nematode.

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