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:
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.
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.
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.
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.
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.
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.