CFAES Give Today
Agronomic Crops Network

Ohio State University Extension

CFAES

Lep Monitoring Network – Western Bean Cutworm and Corn Earworm Update # 12

two moths side-to-side

Over the past week, Western bean cutworm moth reports continue to be on the rise across the state with Sandusky County having the highest average of 47 moths (47 in one trap!). These high numbers mean many counties in Ohio are having peak WBC flight – and should consider scouting for WBC egg masses (more information on this below). Corn earworm monitoring also took place last week, with Lucas County having the highest average of 13.

Figure 2. Western bean cutworm egg masses found on corn plant while scouting. Western Bean Cutworm numbers are peaking in many counties across the state
This past week was our fourth week monitoring for WBC in Ohio. The statewide average for WBC increased slightly from 9.1 during the week ending on July 7th to 9.3 for the week ending July 14th. Counties with the highest averages included Sandusky (47.0), Wood (29.0) and Henry (18.8) (Figure 1). Mid-July is typically when we see WBC moth numbers peak in many counties in OH. High WBC trap numbers means the moths are active, flying, and looking for places to lay eggs. We recommend counties reporting an average of 7 moths or more over the past week consider scouting fields for egg masses. This week these counties include: Defiance, Fulton, Hancock, Henry, Sandusky, Van Wert, Wayne and Wood.

How to scout for WBC egg masses:

  1. Identify fields with corn that is pre-tassel or just starting to tassel.
  2. Examine the upper 3 – 4 leaves of 20 plants in 5 different field locations (100 plants for field), for egg masses (Figure 2).
  3. 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.
  4. 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 4 - July 8th to July 14th, 2024

Figure 1. Average western bean cutworm (WBC) moths captured from July 8th to July 14th. 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.

Corn Earworm
This is our sixth week monitoring for CEW pests in Ohio. The statewide average for CEW decreased slightly from 0.9 during the week ending on July 7th to 0.8 for the week ending July 14th. Counties with the highest averages included Lucas (13.0), Clinton (1.0) and Henry (1.0) (Figure 3). Corn earworm moths tend to be attracted to fields that are in the early green silk stage of development; this is when fields will be most susceptible to damage. 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 6 - July 8th to July 14th, 2024

Figure 3. Average corn earworm (CEW) moths captured from July 8th to July 14th. 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.

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.