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Lep Monitoring Network – Corn Earworm Update # 10

We have just concluded our tenth week of monitoring for Ohio pests and are happy to report on our first week of western bean cutworm moths (WBC) and our third week of corn earworm (CEW). Up until now, scouting numbers for CEW have been relatively low, but this week we have begun to see a turn in the data and an increase in the overall average number of moths per county in Ohio. This past week, Defiance County saw the highest average of WBC moths, and Williams County saw the highest CEW counts, reaching a peak number of 41 moths in one trap. In Van Wert County, it should be noted that while no WBC moths were recorded, several yellow striped armyworms (YSA) were found in the WBC traps – the county has 10 running traps and recorded an average of 2.1 YSA moths per trap this past week.  A special shout-out to Curtis Young for his YSA-spotting.

Western Bean Cutworm

This past week from June 17th to June 23rd we began monitoring for western bean cutworm pests in Ohio. While reports of this pest are low as of now, expect WBC numbers to increase as we get further into the season (they usually peak in July).  We plan to monitor for WBC for 7 weeks, give or take, depending on the numbers scouted. The statewide average for WBC this week is 1.8. Counties with the highest averages included Defiance (2.4), Clinton (2.0), and Auglaize (1.7) (Figure 1). While WBC scouting numbers are currently low, it is still important to be ready for these pests in Ohio and scouting is the best way to stay ahead of any infestations before they happen. As mentioned in last week’s newsletter, western bean cutworm is a common pest of dry beans and a sporadic pest of corn in Ohio. Adults are primarily dark brown and black and can be identified by a distinct comma or crescent-shaped mark in the middle of each wing that is seated behind a light brown to tan colored dot. A white stripe can also be seen along the top edge of the forewing (Figure 2). To continue the conversation and learn more about the western bean cutworm, please visit https://ohioline.osu.edu/factsheet/ENT-40. 

Western bean cutworm moth map

Week 1 - June 17th to June 23rd, 2024

Figure 1. Average western bean cutworm (WBC) moths captured from June 17th to June 23rd. The bold number on the left indicates the average moth count for the week, followed by the standard number on the right which indicates the total number of active traps set up in that county.

Figure 2. Western bean cutworm on an ear of corn. Photo credit: Adam Sisson, Iowa State University, Bugwood.org

Corn Earworm

This is our third week of monitoring for CEW pests in Ohio. The statewide average for CEW increased from 0.12 during the week ending on June 16th to 1.6 for the week ending June 23rd. Counties with the highest averages included Williams (11.8), Clinton (8.0), and Morgan (3.5) (Figure 3). When scouting for CEW pests, these moths are attracted to fields that are in the early green silk stage of development, when fields will be most susceptible to damage. CEW caterpillars vary in color from light to dark but will always have the same characteristic markings. Scouting for the larval stage of these pests is practically impossible, but adult (Figure 4) scouting is important to predict larval damage in a field. To monitor CEW moths, we are using green bucket traps with a lure that attracts adults to the trap. Traps are checked weekly, and an average is reported for each monitoring county. To learn more about corn earworms, check out one of our previous newsletters: https://agcrops.osu.edu/newsletter/corn-newsletter/2019-27/corn-earworm-field-corn-watch-molds

Corn earworm moth map

Week 3 - June 17th to June 23rd, 2024

Figure 3. Average corn earworm (CEW) moths captured from June 17th to June 23rd. The bold number on the left indicates the average moth count for the week, followed by the standard number on the right which indicates the total number of active traps set up in that county.

Figure 4. Corn earworm caterpillar on leaf. Photo credit: Whitney Cranshaw, Colorado State University, Bugwood.org

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.