Issue No. 8, Article 1/May 28, 2010
General Entomology Observations and Wireworm "Tidbits"
On May 24, extension entomologists met via teleconference again to share observations collected throughout the north-central region. My general impression: overall, insect activity has been relatively quiet this spring. In some areas of northeast Ohio, slugs are creating challenges for producers, and in some wheat fields, cereal leaf beetles are being sprayed. In Nebraska, entomologists have reported that pillbugs (isopods, not insects) are feeding in some no-till soybean production fields.
Thus far, bean leaf beetles across the region appear to be at very low levels. Is the widespread use of systemic insecticidal seed treatments on soybean seed having an effect? Is the harsh winter primarily responsible for low densities? Erin Hodgson, Iowa State University Extension entomologist, shared some predictions on bean leaf beetle infestations for 2010 earlier this spring. Across Iowa, Erin indicates, the harsh winter means that bean leaf beetle mortality should range from 82% to 99% across the state. For the northern third of Illinois, survival should have been similarly low this past winter.
As of May 26, I have received no confirmation that corn rootworm larvae have hatched; however, I suspect that the beginning of this annual event is underway.
Ron Hines has provided an interesting photograph of wireworm adults (click beetles) on the leaf surface of corn plants (V5 growth stage) in Massac County, Illinois. The field of no-till corn (following soybeans) had experienced some reduction in stand. Wireworms belong to a large family (Elateridae) of beetles, with approximately 840 species described for North America. The "click beetle" nickname comes from the sound made when adults right themselves when placed upside down on their wing covers. The adults are characteristically torpedo-shaped (elongate), with the posterior corners of the pronotum pointed. Females lay their eggs in grassy areas or within cultivated sites. Larvae are very long-lived; depending on the species they may live from 1 to 5 years in the soil profile before they become adults.
Wireworm adults (click beetles) on corn plants (V5 growth stage) grown in Massac County, Illinois (May 21, 2010). Courtesy of Ron Hines.
As temperatures warm in the spring, wireworm larvae descend further into the soil and become difficult to locate. Rescue treatments have proven ineffective for wireworms, and a soil insecticide used at planting has been the primary management tactic. Bait stations have been suggested as a way to predict potential economic infestations; most producers have chosen not to use this approach, however, due to the number of bait stations required to adequately sample a field and time constraints in the spring.--Mike Gray