Corn Earworm

Losses from Corn Earworm have been estimated as high as 7% and populations may reach economic infestations of 35 million acres across the entire United States. Between the difficulty of effectively controlling Corn Earworm with insecticides and the damage generally being overlooked until harvest, many farmers have elected to accept the lost yield potential. New tools are becoming available to combat Corn Earworm and help protect yield potential.

Identification

Life Cycle

There are usually two generations in much of the Midwest. Corn Earworms migrate in from the south with winds and storms from southern states. Moths typically lay eggs in corn and other host crops. The first generation larval stage feeds in the whorl of corn and other food sources, although first generation damage is generally minimal.
First generation moths lay eggs on corn silks, and larvae travel down silks within one hour of hatching. The larvae then feed on kernels for the most of the larval stage.

Management

Planting early can help avoid peak moth flights, and corn with tight husks can help reduce feeding potential. Several foliar insecticides are labeled for control of Corn Earworm; however, the contact needed between larvae and foliar insecticides for good efficacy is rare due to larvae burrowing down the silks soon after hatching.

Sources: K.A. Cook and R. Weinzierl. 2004. Corn Earworm Insect Fact Sheet.Univ. of Illinois Integrated Pest Management. K. L. Steffey and others. 1999. Handbook of Corn Insects. Entomological Society of America.

Western Bean Cutworm

Western Bean Cutworm is a relatively new pest to the Midwest. Although it was a pest of dry bean, it is now a serious threat to corn in some parts of the Corn Belt. Properly identifying Western Bean Cutworm and understanding its thresholds can help determine if control options are needed.

Identification

Life Cycle

Corn fields in the late-whorl stage are target locations for females to begin laying eggs. Egg masses of 5 to 200 are usually laid on the upper surface of the top leaves, and most are laid during peak moth flight in late July or early August. Timing of moth flights must be compatible with the corn stage for ear feeding. Larvae first feed on pollen, then on corn ears for several weeks before they drop to the soil and overwinter.

Management

Western Bean Cutworm larval feeding damages corn through reduced grain yield and quality. Pollination may be poor if silks are damaged from feeding. Once the ear is formed, Western Bean Cutworm feed on developing kernels and can destroy as much as 50 to 60% of them. Losses may be compounded by subsequent fungal and mold infections associate with larval waste products.

Scouting for Western Bean Cutworm should start when moth flights begin, usually in mid-July. Check 20 consecutive corn plants at five different locations in the field. An insecticide application has been historically recommended if 8% of the plants contain and egg mass of if young larvae are found in the tassel.

Sources. E. Cullen. 2008. Wisconsin Crop Manager. Volume 15 Number 22, Aug 7, 2008; R. Seymour and others. 2004. Western bean cutworm in corn and dry beans. Univ. of Nebraska Ext. NebGuide G1359; B. Wright and R. Seymour. 1996. Western bean cutworm management. Univ. of Nebraska Extension. PM Guide. http://entomology.unl.edu. 6/10/09; K.L. Steffey et al. 1999. Handbook of Corn Insects. Entomological Society of America.