The Lep monitoring network continues to monitor for both Western bean cutworm and corn earworm moths in Ohio. Western bean cutworm moth reports are on the rise across the state with Wood county having the highest average of 28.8 moths (a total of 70 in one trap!). These high numbers indicate certain counties should start 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 9.
Western Bean Cutworm numbers are on the rise across the state
This past week was our third week monitoring for WBC in Ohio. The statewide average for WBC increased immensely from 0.7 during the week ending on June 30th to 9.1 for the week ending July 7th. Counties with the highest averages included Wood (28.8), Hancock (19.3) and Defiance (17.3) (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. This means counties with an average of 7 moths or more over the past week should consider scouting fields for egg masses.
How to scout for WBC egg masses:
Once moth numbers increase to 7 or more a week, it is an indicator that the moths are active in your county and looking for a place to lay eggs. Identify fields with corn that is pre-tassel or just starting to tassel and examine 20 plants in 5 different field locations (100 plants for field). Eggs are laid on the top 3 – 4 leaves of the plant. Newly laid egg masses are a white/cream color that darken as they mature to a dark purplish color (Figure 2). 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
Another thing to note, when monitoring for WBC adult moths, it is important to be aware of imposters that may find their way into WBC traps and are easily confused with true WBC moths. The imposter WBC’s look practically identical to their harmful counterparts and the primary distinguishing feature between the two is size. Imposters tend to be significantly shorter in length when compared to true WBC’s (Figure 3). 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 3 - July 1st to July 7th, 2024
Corn Earworm
This is our fifth week monitoring for CEW pests in Ohio. The statewide average for CEW increased from 0.4 during the week ending on June 30th to 0.9 for the week ending July 7th. Counties with the highest averages included Lucas (9.0), Clinton (3.0) and Henry (1.8) (Figure 4). 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. 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 impossibly, but adult (Figure 5) monitoring is important to predict larval presence in a field. 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 5 - July 1st to July 7th, 2024
