July 9, 2010

Corn blotch leafminers are injuring whorl stage corn in many areas of central Nebraska. The corn blotch leafminer is an immature stage of a fly. The larva tunnels inside corn leaves, leaving hollowed out whitish tunnels where it has fed. High populations may kill several of the lower leaves of whorl stage corn.

There are several generations per year in Nebraska, but typically the first generation on corn does the most injury. Field observations indicate that this first generation is near the end of its feeding. As corn matures, the leaves thicken and later generations of the maggot tunnel in only the lower or upper half of the leaf, causing less damage.

Foliar insecticides are not recommended for control of these insects. The adult flies emerge over several weeks and would be difficult to economically control with insecticides. The egg and immature stages are inside the leaf and protected from insecticides. Additionally, broad-spectrum insecticides have the potential to kill many predatory and parasitic insects which help suppress other corn pests such as spider mites and aphids, and may lead to greater pest problems later in the summer.

For more information see Corn Blotch Leafminer (NebGuide 1635).

Bob Wright
Extension Entomologist