Issue No. 9, Article 3/May 20, 2005
Assessing Early-Season Corn for Insect Injury
With all of the challenges to early-season establishment of corn seedlings this year, insect injury is only one item on the checklist. However, it's important to assess the impact of secondary insect pests of corn in light of the scarcity of modern data regarding the percentage of acres affected, the economic impact of feeding by secondary insect pests, and the efficacy of insect-control products. We are particularly interested in obtaining data from side-by-side comparisons of treated (e.g., insecticidal seed treatment, soil insecticide) versus nontreated corn. On occasion, we hear reports that a given insecticidal seed treatment did not provide acceptable protection against cutworms, white grubs, or wireworms, although such testimonials have little bearing without supporting data. We have established a few trials, but data from numerous locations would let us assess the situation with more clarity.
Entomologists from other states are just beginning to report on secondary insect pests of corn. Marlin Rice, extension entomologist at Iowa State University, recently wrote an article that indicated that insecticidal seed treatments may not stop larger instar (e.g., fourth instar) cutworms. Ric Bessin, extension entomologist at the University of Kentucky, reported some wireworm problems in central Kentucky, and he indicated that insecticidal seed treatments or soil insecticides had been used in some of the affected fields.
We have received only a few reports of injury caused by cutworms, white grubs, and wireworms this spring. We have yet to hear about infestations of some of the other secondary insect pests, such as grape colaspis and southern corn leaf beetles. So, as a reminder, if you observe infestations of any of these pests, let us know.--Kevin Steffey