Armyworm Flight 2009: No consistent story; but there will be caterpillars!

Doug Johnson, Extension Entomologist
Dept. of Entomology, University of Kentucky

Early captures of armyworm moths appeared to indicate a larger than normal population for 2009. However, after several weeks of monitoring it appears that the capture counts do not indicate an obvious major outbreak situation. This is particularly true of the Princeton, KY trap. We do not yet have enough historic data to know how to interpret the Lexington trap data. However, this does NOT mean that there will not be any problems. [Please see: How to Use Insect Graphs from the UK-IPM Trap Lines at:

http://www.uky.edu/Ag/kpn/kpn_09/pn_090324.html

to review how to use the trap data.]

There will be armyworm caterpillars in susceptible host (corn, small grains, grass forages), as there are every year. In fact if we apply the day degree model to the very first moth captures there are likely caterpillars already appearing in both western and central Kentucky. These will be among the earliest of caterpillars. Remember if you are in a location warmer than where our traps are located then caterpillars will appear earlier. If you are in a cooler location they will appear later. I have received one report of armyworm caterpillars on the heads of wheat (though I have not seen this myself) from a southern Pennyrile area county.

While moth captures in our traps do not indicate a major outbreak year, we certainly have experienced weather that selects for the survival of the caterpillars. Typically armyworm populations do better in cool wet weather. At least in western Kentucky we have certainly seen such weather. Historically, grass forages and corn suffer the most damage from armyworm, but small grains are certainly at risk, particularly if the caterpillars are feeding on the heads.
Scouting techniques and thresholds are available in our IPM Manuals available at:

http://www.uky.edu/Ag/IPM/manuals.htm

If needed, insecticide recommendations are available in our Insect Management Recommendations for field crops available at:

http://pest.ca.uky.edu/EXT/Recs/welcomerecs.html

These publications may also be available at your local County Extension office.

Even though our trap counts do not suggest a big problem, the weather patterns certainly imply that scouting susceptible hosts is still important. I request that anyone that finds an armyworm infestation that requires treatment or should have been treated, please let me know at: doug.johnson@uky.edu.