Corn Rootworm Egg Hatch Officially Under Way

June 4, 1999
In several previous issues of the Bulletin, we've offered heat-unit accumulations that could be used to predict the hatch of corn rootworm eggs. On June 1, entomologists at Purdue University reported that the hatch of rootworm eggs is officially under way in central Indiana. First-instar larvae are very difficult to find because of their size and preference to feed internally within root tissue. To observe first instars within corn roots, entomologists must first stain roots in the laboratory. Corn rootworms have three larval instars (an instar is the stage between molts, the physiological process by which grubs shed their skins). When rootworms reach the final growth stage (later this month), they are much easier to find; however, even a full-grown rootworm grub is only 1/2 inch in length. In upcoming issues of the Bulletin, we'll provide some projections for adult emergence.--Mike Gray

Author: Mike Gray