In general, economic losses occur after one or more primary roots are chewed to within 1.5 inches of the plant. Grain losses from Colorado State University studies have averaged 10 per cent over the last decade. By mid July, most larvae have finished feeding and transformed into adult beetles. They emerge from soil to feed, mate and lay eggs. These eggs produce the larvae that will attack the following year's crop.
Females prefer moist area, so eggs are concentrated in the soil between rows in irrigated corn.
Heavier soils with organic matter content of 1.5 per cent also are preferred. This is the most consistent and economical means of controlling rootworms. Early Planting Fields that have completed pollen shed are not very attractive to rootworm adults. Early planted fields can be through pollination before majority of adults have emerged and therefore less egg laying activity. Early planted fields also will have relatively larger root systems when rootworm feeding starts.