Kevin Black with Growmark in Bloomington has indicated that he has received more than a "typical" number of reports of crane fly larvae in some fields this spring. Given the amount of rain that has fallen this year and crane flies' proclivity for wet conditions, this is not surprising. However, crane fly larvae are not pests of corn, so it's very important that they not be mistaken for cutworms. |
Crane fly larvae often are found curled head to tail, very much resembling cutworms at rest in the soil. However, the absence of both true legs and prolegs distinguishes crane fly larvae from cutworms. In addition, a crane fly larva's head is narrow and often retracted into the segments of the thorax. The last abdominal segment has two dark, circular spiracles, or breathing pores, and may have fleshy projections. Crane flies usually occur in damp situations where decaying plant material is abundant. As usual, Marlin Rice, extension entomologist at Iowa State University, has the best photograph of a crane fly: http://www.ipm.iastate.edu/ipm/icm/2001/ 5-7-2001/earlyscout.html.
Because crane flies do not injure corn, insecticides are not necessary for their control. Don't make the mistake of applying an insecticide to control a "pest" that's not a pest. Rely on your diagnostic skills before you make a hasty decision, and if you are in doubt, send the specimens to us. We'll do our best to answer your questions quickly.--Kevin Steffey