Not surprisingly, bean leaf beetles are abundant in early-planted soybean fields. Where a lot of soybeans went into the ground at about the same time, bean leaf beetle populations are "diluted" over the area. However, in areas where some fields were planted early and other fields have just been planted or have yet to be planted, bean leaf beetle densities are quite high in the early-planted fields.|
Keith Evans with FMC Corporation examined seven soybean fields in east-central Illinois and observed 20 to 40 percent defoliation on unifoliolate leaves. This level of defoliation probably is not economic, as long as the soybean plants are growing vigorously. However, in fields where bean leaf beetles are active, the progress of injury should be monitored carefully.
Bean leaf beetles will disappear from soybean fields soon, after they have consumed enough leaf tissue to obtain energy for egg production and oviposition. I'm still guessing that many bean leaf beetles will not survive because of the lack of availability of soybeans. However, these types of predictions are always risky, so we'll see what the season brings.--Kevin Steffey