The largest-ever recorded capture of fall armyworm moths occurred during the week ending on Aug. 27 in the Integrated Pest Management traps at the University of Kentucky Research and Education Centerin Princeton.

Grain crops and alfalfa/grass forage producers should be on alert for the first appearance of caterpillars, which should occur in the next week or two, said Doug Johnson, Extension entomologist with the University of Kentucky College of Agriculture.

Trap counts on Aug. 27 were 1,038 moths. This is a phenomenal increase from 52 moth captures the week before. In the 15 years the IPM traps have been collected in Princeton, the second-highest number of moth counts came in at 326 for the week of Oct. 5, 2007, which was an outbreak year.

"It is always possible nothing unusual will happen, but fall armyworm damage to forage fields has already occurred in at least four western Kentucky counties this season," he said.

While western Kentucky trap count numbers are extremely high, the moth captures in Lexington have remained low.

The fall armyworm is a pest that migrates to Kentucky from the South each summer, usually arriving in late June or early July. While fall armyworms are typically not a major pest, they cause the greatest damage in late-planted corn, grain sorghum, alfalfa and double-crop soybeans. Due to the timing of this large capture, grasses and alfalfa-especially newly seeded stands, late-maturing beans and wheat seedlings will be at the greatest risk of infestation.

While it is a pest of cattle and horse pastures, the fall armyworm should not affect horses. It should not be confused with the eastern tent caterpillar that causes mare reproductive loss syndrome. Fall armyworms appear in Kentucky only in late summer and fall. Eastern tent caterpillars appear in the spring. A third caterpillar species, the fall webworm, might cause additional confusion. It produces silken webs in trees that some people might mistake for those of the eastern tent caterpillar. Again fall webworms appear in the late summer and fall, not in the spring, Johnson said.