Could Fall Armyworm Be A Threat Now??

Doug Johnson, Extension Entomologist, University of Kentucky

It seems completely ridiculous to me to be talking about fall armyworm (FAW) at this time of year in Kentucky.  So far we have not detected this insect in our UK-IPM pheromone baited traps at Princeton or Lexington and I have not heard of any detections in TN. Unfortunately, Arkansas is reporting an “outbreak” of this insect, and that gives me a little pause. In most years I would not expect to detect this insect until mid or late July and with the exception of very late planted corn in the purchase region, I would not expect it as a problem until August.

The other confusing part of this situation is that we don’t know which feeding strain of FAW this might be. Caterpillars of these two strains look identical, one cannot tell them apart except by what they eat, or DNA analysis. The “corn” feeding strain would be a problem on all corn products and grain sorghum. The “grass” feeding strain is largely a problem on forage grasses especially Bermuda, but also including millet. Most of our wheat is too far along for FAW to be a problem.

Though I think problems are unlikely in the short run, Anyone:

• ·         In the western 1/3 of the state (especially the Jackson Purchase counties) and
• ·         Have late planted or replanted corn and/or
• ·         growing corn products that do not contain GMO foliar feeding traits, or
• ·         or are producing forage grasses especially Bermuda grass, and millet;

 should be on the lookout for this pest in their fields.

 

Figure 1. Fall armyworm on corn.

Remember FAW  and armyworm (AW) are two different insects. However, these pests overlap a great deal in what they eat. Normally, AW would have already appeared and be close to finishing their cycle by now and FAW should just be arriving. FAW larvae vary from light tan to nearly black with three thin light yellow lines down the back. There is a wider dark strip and a wavy yellow-red splotched stripe on either side. FAW can be confused with both AW corn earworm, but FAW has a prominent white inverted Y mark on the front of the head (See Figure 1). Generally, FAW is a bit more difficult to control than is armyworm. The most difficult situation for FAW control is, when the caterpillar is tunneling head first, down into the corn whorl, while at the same time defecating a fecal plug above its self, which prevents foliar insecticide from contacting the insect. So, detection before this stage and good application are both important for good control.