–by Dr. Jeff Whitworth — Field Crops
Western corn rootworm adults have been emerging throughout north central Kansas since at least 6 July. One relatively easy and quick method of detecting corn rootworm adults if they emerge prior to tasseling/silking is to look for characteristic signs that the adults have/are emerging and feeding on leaves (see fig. 1) This type of leaf feeding, where the beetles just feed on the top side of the leaf, is very characteristic of adult western corn rootworms– this type of leaf injury can be from other causes, but is very symptomatic of adult western corn rootworms. They will move up to feed on the silks, however, when they start emerging (see fig. 2, from 14 July). Please remember, if there is a 50%+ adult infestation (5 adults/10 plants, etc.) this year in any continuous corn fields, those fields should be considered for a corn rootworm control method (adult spray this year-crop rotation, etc.) if destined for corn next year.
Figure 1. CRW leaf feeding
Figure 2. Corn rootworms (note the gravid female at the top)