In Iowa, the species of corn rootworm (CRW) that are of economic importance include western corn rootworm Diabrotica virgifera virgifera LeConte and northern corn rootworm D. barberi Smith and Lawrence, and these two species are the most damaging pests of corn, Zea mays, in the United States Corn Belt. Eggs are laid in the soil during the summer and hatch the following spring. Larval feeding on corn roots in June may diminish yield by reducing plant growth and drought tolerance, and by imposing harvest losses due to plant lodging. Adult emergence from the soil is underway by early July, with most adult emergence completed by mid-August. Additional crop losses may be caused by adult beetles feeding on corn silk and soft doughy kernels. In Iowa, crop rotation, where it fits cropping practices, remains the preferred method of management. However, it is also economically feasible to protect corn roots with soil-applied insecticides and plant incorporated protectants, which are transgenic corn hybrids that produce insecticidal toxins derived from Bacillus thuringiensis (Bt).