Western bean cutworm (WBC) trap counts for the week of July 13 – 19 continue to increase in many Ohio counties. A total of 27 counties monitored 91 traps resulting in 467 WBC adults (5.1 average moths per trap) (Figure 1). Counties that are averaging more than 7 moths per week should begin monitoring for egg masses (Figure 2). These counties include Fulton, Huron, Lucas, and Sandusky. While numbers of WBC moths increased from the previous week, the general trend of WBC for 2020 is currently low compared to previous years (Figure 3).
Scout pre-tassel corn approaching tassel fields. Choose at least 20 consecutive plants in 5 random locations (scout different areas of the field that may be in different growth stages). Inspect the uppermost 3–4 leaves. Consider treatment if >8% of inspected plants have eggs or larvae (field corn) or in sweet corn, if >4% of inspected plants have eggs or larvae (processing market), or >1% of plants (fresh-market).
If the number of egg masses/larvae observed exceed threshold, many insecticides are available to adequately control WBC, especially those containing a pyrethroid. However, as with any ear-burrowing caterpillar pest, timing is critical. Insecticide applications must occur after egg hatch, or after tassel emergence, but before caterpillars enter the ear. If eggs have hatched, applications should be made after 95% of the field has tassel. If eggs have not hatched, monitor for the color change. Hatch will occur within 24–48 hours once eggs turn purple. To search for larval injury after it has occurred, search the corn for ears having feeding holes on the outside of the husks.