Corn earworm eggs and larvae on leaf
Article is taken from https://agcrops.osu.edu/newsletter/corn-newsletter/2024-24/lep-monitoring-network-%E2%80%93-time-scout-western-bean-cutworm-update by Stephanie Pflaum, Amy Raudenbush, Maddie Brillhart, Trevor Corboy, Allen Gahler, Don Hammersmith, Mary Jo Hassen, Ed Lentz, CCA, Kendall Lovejoy, Sarah Noggle, Les Ober, CCA, Jordan Penrose, Beth Scheckelhoff, Mike Sunderman, Frank Thayer, Kyle Verhoff, Jacob Winters, Kayla Wyse, Curtis Young, CCA, Andy Michel, Kelley Tilmon
We have just finished out our fourteenth week of monitoring at the Lep Network. This past week, we saw WBC numbers trending down and CEW numbers close to zero across the state. Western bean cutworm numbers topped out with Sandusky County having the highest average by far of 38 moths. As for corn earworm, Putnam was the only county to report any CEW sightings for this past week and averaged 0.3 moths in the county. Western bean cutworm populations across Ohio have most likely hit their peak numbers of the season and a decline should be expected. While we are most likely beginning to round out of the peak for this pest, any counties with averages that are still above 7 should continue scouting until their county numbers have declined.
Western Bean Cutworm numbers are peaking in many counties across the state
This past week was our fifth week monitoring for WBC in Ohio. The statewide average for WBC decreased substantially from 9.3 during the week ending on July 14th to only 1.9 for the week ending July 21st. The counties with the highest averages are Sandusky (38.0) and Lorain (8.0) (Figure 1). Here at the Lep Network, we are fairly certain that we have already seen our peak in WBC moths for this year and are starting the decline. Despite this shift in numbers, it is still important to be scouting for WBC egg masses (Figure 2), especially if this week’s average topped 7 moths in your county. Counties that should continue scouting this week are: Defiance, Huron, Lorain, Sandusky, Wayne, and Wood.
How to scout for WBC egg masses:
- Identify fields with corn that is pre-tassel or just starting to tassel as these pests need tassels to feed on until the full ear forms.
- Examine the upper 3 – 4 leaves of 20 plants in 5 different field locations (100 plants for field), for egg masses (Figure 2).
- Record the number of egg masses found. Newly laid egg masses are a white/cream color that darken as they mature to a dark purplish color.
- If 5% of plants have egg masses, a treatment may be necessary. Be sure to time the treatment when the majority of the egg masses are mature (purple).
To view a more detailed video on scouting – click here: https://youtu.be/qGjpwtfkObM?si=CFPzX1rlqt6jzyJw
Western bean cutworm moth map
Week 5 – July 15th to July 22nd, 2024
Figure 1. Average western bean cutworm (WBC) moths captured from July 15th to July 22nd. 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 egg mass on leaf. Photo credit: Frank Peairs, Colorado State University, Bugwood.org
Corn Earworm
This is our seventh week monitoring for CEW pests in Ohio. The statewide average for CEW has continued to decrease from 0.8 during the week ending on July 14th to just 0.02 for the week ending July 21st. The only county with any recorded moths was Putnam (0.3) (Figure 3). Expect reports for CEW to continue to be low for the remainder of its season. To learn more about the corn earworm, 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 7 – July 15th to July 22nd, 2024
Figure 3. Average corn earworm (CEW) moths captured from July 15th to July 22nd. 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.