Corn Earworm Moth Counts Increasing Significantly.

Author: Doug Johnson, Extension Entomologist

Capture of corn earworm moths in IPM pheromone-baited traps in Princeton, (Caldwell Co.) KY and in Fulton Co. KY have taken a significant increase over the past two to three weeks. This follows on the heels of warnings of corn earworm problems in states south of KY.

The counts in Cam Kenimer’s Fulton Co. traps are by far the largest, with a capture of 547 moths on 8/5/12 and 486 on 8/12/12. Numbers are increasing in Princeton, too, with 200 captured during the trap week ending 8/2/12 and 206 for the week ending 8/9/12. This is a substantial increase compared to the rest of the year. The increase also came earlier in the year by several weeks and is much larger when compared to the rolling five year average. ( See:

http://www.uky.edu/Ag/IPMPrinceton/counts/cew/cewgraph.htm)

These insects are likely coming out of corn that is maturing and will be looking for another host, probably soybean on which to lay their eggs. The moths are not the damaging stage, but in a couple of weeks, their offspring will appear in the form of caterpillars.

The first really big jump in capture was in Fulton Co. on July 22, but that capture is only about 1/3 of the most recent capture. Using July 22 as a starting date, small larvae to medium larvae could already be present. Larvae from moths caught over the last couple of weeks should come in a steady stream.

With corn maturing and being harvested in most western KY areas, soybeans are the most likely field crop target for this pest. Of course these counts cannot predict what will happen in a particular field. Conversely, the captures are certainly above the rolling five year average so represent an increased level of risk. Areas in the south and west will be impacted sooner and areas in the north and east somewhat later. You should be scouting your soybeans NOW!

Newly hatched CEW larvae are translucent yellowish-white, but larger larvae have considerable color variation. When feeding on soybeans they tend to be light reddish- brown and large larvae are often green, yellowish or black with distinct cream colored bands running their length and their heads are usually orange.

CEW can consume foliage, flowers and pods of both full-season and double-crop soybeans. Economic threshold in wide row (30”) beans sampled using the 3’ shake-cloth method would be two worms per row foot. If sweeping (15” sweep net) narrow row beans the threshold would be an average of 9 caterpillars per 25 sweeps.

If insecticidal control is warranted, suggested insecticides may be found in ENT- 13 which you may obtain from your county extension office or on line at: http://pest.ca.uky.edu/EXT/Recs/welcomerecs.html