Submitted by Louis Sutton, AgVenture's Product & Technology Manager/Sorghum Lead
Japanese beetles can be a major pest on soybeans and corn field. Here are a few thoughts...
Scout five areas in the field, if 20% of the leaf structure of soybeans are defoliated in the check areas, then a treatment is needed.
On corn, if three beetles are found per ear, a treatment is required if the corn is still pollinating. I would treat if I found three on any ear as this can be a very distructive pest. In corn, the beetles will feed on the silks and the ear, they have been known to feed on young tassels. When scouting the field, pay close attention to the borders as the beetles will show here first normally and if caught early may only need to treat the borders.
When treating for Japanese beetles, scouting after the treatment is required as a population flare-up can occur with a pest species like aphids and/or spider mites if they are present in the field. Also, the beetle will reinfest the field and may need to be treated again depending on how aggressive the infestation is, so keep rescouting fields for the pest pre and post spray.
If you have additional questions, please comment or contact your local Regional Seed Company.