Western Bean Cutworm
Western bean cutworm (WBC) averages have increased in many counties across Ohio from July 18 - 24. For the week ending July 24, the statewide average was greater than 9 moths, an increase from the 8 moth average last week. We recommend that any counties that reported an average of 7 or more moths within a week should begin scouting for egg masses. Over the past week 14 counties reported an average of 7 or more moths including: Ashtabula, Coshocton, Defiance, Erie, Fulton, Geauga, Hancock, Huron, Lucas, Paulding, Portage, Sandusky, Trumbull, and Williams (Figure 1).
Western Bean Cutworm Moth Map
July 18 – 24, 2022
Scouting guidelines
1) Counties reporting an average of 7 or more moths within a week should scout for WBC egg masses (Figure 2).
2) Randomly choose 20 consecutive plants in 5 locations within a field (a total of 100 plants per field).
2) Inspect the uppermost 3–4 leaves of the corn plant. It is helpful to look at the leaves with the sun behind them. Oftentimes the shadow of the egg mass will show through the leaf without having to examine the leaf closely.
3) Record the number of plants with egg masses or larvae to calculate the percentage of plants with WBC present.
For more scouting information, view our WBC scouting video https://aginsects.osu.edu/news/western-bean-cutworm-video
Treatment Recommendations
Field corn should be treated with a foliar treatment if more than 5% of inspected plants have eggs or larvae. Sweet corn should be treated if more than 4% of inspected plants have eggs or larvae (processing market), or 1% of plants (fresh-market). Timing an insecticide application is critical and must happen before the caterpillar enters the ear, but after the eggs hatch. If the eggs have hatched, applications should be made after 95% of the field has tassels. If the eggs have not hatched, monitor the egg masses for the color change. When the egg masses are first laid they are a whiteish color. As the egg masses mature, they turn a purplish color. Hatch will occur within 24–48 hours once eggs turn purple.
Corn Earworm
The number of Corn Earworm (CEW) numbers remain low but did slightly increase this past week. Brown county numbers increased from last week and overtook Van Wert County as the highest out of all monitoring counties with an average of 7 moths (Figure 3).
Corn Earworm Moth Map
July 18 – 24, 2022
Fall Armyworm
Of the 5 counties that are monitoring Fall Armyworm (FAW), 4 counties have reported catching FAW the week of July 18 – 24, an increase from only 2 last week. Clark reported the most FAW with 4, an overall decrease from their 6 last week (Figure 4).
Fall Armyworm moth map
July 18 – 24, 2022
European Corn Borer
This week’s numbers for European Corn Borer (ECB) have remained steady with no counties reporting of finding any ECB for the second week in a row (Figure 5).
European Corn Borer Moth Map
July 18 - 24, 2022