Contributed by Ken Wise – NYS IPM Program
This week near Kinderhook in Eastern NY there is a large infestation of fall armyworm larvae in a 50 acre alfalfa field. The larvae completely ate all of the alfalfa leaflets leaving only the stems on the 50 acres. They were in the 2nd to 3rd instar of development. This means they are still small. Fall armyworm normally go through 6 instars and will eat much more forage before they pupate. The range of the infestation was 5 to 15 larvae per square foot. Fall armyworm in other parts of the country has been causing issues this season. It would be best to go out and check your crops for fall armyworm. The threshold for fall armyworm in alfalfa is 1-3 larvae per square foot. Many of the Bt corn hybrids are resistant to fall armyworm. Fall armyworm will feed on many other grasses. It is best to get out and scout fields now!
There will be more information on insecticides that can be used on field crops for fall armyworm coming this week!
