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Western corn rootworm
Photo by Tom Hlavity, USDA ARS, Bugwood.org
The adult western corn rootworm has emerged nearly one month early. In the fields where plants have not begun to tassel and shed pollen, beetles are feeding on corn-leaf epidermal tissue and will continue to do so until pollen and silks become available. "Leaf injury reduces the plants' photosynthetic efficiency, so some yield loss should be anticipated for those fields, particularly those that are under moisture stress," Gray says.
As silks become available, a rescue treatment should be considered if there are five or more beetles per plant, silks have been clipped to less than 1/2 in. of the ear tip and the pollination process is not complete. While scouting for silk clipping, look for lodged or goose-necked plants. This is evidence of larval injury to root systems.
"If lodged plants are observed, dig up some of the plants, wash the soil from the root systems, and look for signs of feeding or pruning," Gray advises. "If excessive injury is found, contact your seed company representative."