Last week, we were asked when a grower should be concerned about adult corn rootworms feeding on the silks of their corn. The importance of beetle feeding on corn silks is variable and there is not a definitive treatment threshold. The variability is the result of the environmental conditions and the maturity of the corn in relation to surrounding fields. During the 1970s, Purdue University conducted a study to try to identify a treatment threshold for adult rootworm feeding. The resulting threshold was 5 to 15 adult rootworms per plant.