By Jon Tollefson and Erin Hodgson, Department of Entomology
This is a very good time to walk corn fields and check the plant stand. Estimating your plant stand will help you know what plant population actually emerged compared to what you thought you planted. And it will help you scout for early-season insects and disease.
There are several insects that might be decreasing your plant stand right now. We have had reports of dingy cutworms, black cutworms, wireworms, and armyworms. You can still take action against the black cutworms and armyworms. Even though it is too late to treat for wireworms now, finding them in corn fields can help you be prepared for them next year.
Cutting of corn by black cutworms was in progress by the end of last week and should now be happening in central and northern Iowa, as reported in the ICM article Predicted black cutworm cutting dates in corn. This insect can be stopped with foliar insecticide sprays. A recent ICM Newsletter article, Dynamic BCW Action Threshold, provides calculation aids for the treatment thresholds that should be used.
Update on wireworm presence in Iowa
An unexpected event with the wireworm in Iowa and surrounding states is that they have caused stand loss in fields of corn where the seed had been treated with Poncho 250. If you have planted seed with a Poncho treatment, don't ignore it. If there is stand loss from wireworms in those fields you might consider going to the higher rate (Poncho 1250) next year or to treat the fields with a granular insecticide instead.
Jon Tollefson is a professor of entomology with responsibilities in research and extension. He can be reached at (515) 294-8044 or firstname.lastname@example.org. Erin Hodgson is an assistant professor of entomology with extension and research responsibilities. She can be contacted by email at email@example.com or phone (515) 294-2847.