Corn rootworm larvae. (Marlin E. Rice)

Troy Koehler, Certified Crop Specialist, New Century FS, Inc., Toledo, has been finding high populations of small corn rootworms in first-year corn in Marshall County since Memorial Day weekend. He brought specimens by my office for confirmation; some of the larvae appear to be second instars. Kevin Black, Insect/Plant Disease Technical Manager, GROWMARK, Inc., notes that the areas most heavily affected include Albion, State Center, and east of Malvern and that "this is the second or third year for severe rootworm damage in first-year corn in this area." Additionally, he notes that "8-9 larvae are being found per root system by simply checking in the soil." Kevin suspects, based on past reports from this area, that the problem is caused by extended diapause northern corn rootworms and not the variant western corn rootworm.

Producers with first-year corn fields that are unprotected against corn rootworm larvae may want to consider examining corn roots and adjacent soil for rootworm larvae. If an average of one larva per plant is found, a rescue liquid insecticide, such as Furadan®, should be considered.

Marlin E. Rice is a professor of entomology with extension and research responsibilities.