This threshold can be used either for determining the need for a soil insecticide in the following year or for determining the need to apply an adult treatment during the current season. A second adult treatment should be considered if beetle densities rebound to above 12,000 per acre. It has proved difficult to prevent egg laying for the season with a single treatment of most of these products. An exception may be Capture 2E which, in our limited testing, has provided adequate season-long control. In addition to efficacy, there are two important considerations in selecting an adult rootworm insecticide.
Spider mites are a serious pest of field corn in Colorado.
Some outbreaks occur naturally while others are triggered by insecticides applied to control other corn pests. One reason for such secondary outbreaks is that the insecticides kill important natural enemies of the spider mites. There is also some evidence that certain corn insecticides have behavioral or physiological effects on the spider mites that contribute to outbreaks. The need to control corn rootworm adults occurs at or after tasseling, at the same time that spider mite densities normally start to increase. All insecticides labelled for adult rootworm control, with the exceptions of Capture 2E and Furadan 4F, can be expected to provoke corn spider mite outbreaks under some conditions.