Aaron Gabriel, CCE Capital Area Agriculture and Horticulture Program
True Armyworm are being found across New York State. I have found several larvae in fields so far in Washington and Schenectady counties. In one hay field in three samples, I found one, five, and three small larvae per square foot were found.
Basic Information on Armyworm:
- Armyworm eat grasses – corn, hay grasses
- The immatures (larvae) are caterpillars that hatched from an egg laid by a moth. Moths and larvae are nocturnal.
- Right now the larvae are small (3/8 inch) and a couple are medium in size (1/2 inch). Large larvae do much more damage than smaller larvae. So, we can prevent crop damage if we scout through June and monitor size and numbers of larvae in our crops. Look for larvae as well as eaten leaf edges, ragged leaves, and look for dark green excrement (BB size or smaller, slimy at first, then it will dry out with age). You will find larvae climbing plants at night, and hiding on the soil surface during the day, since they are nocturnal. Monitor regrowth of hay fields, larvae will consume new blades and the field will not regrow.
- The action threshold for whorl-stage corn in NY is three larvae per plant. For older corn treat if feeding damage occurs above the ear. For wheat treat if there are 3 or 4 larvae per square foot. We have no action threshold for hay, but a few years ago in our last infestation, entire fields of grass were eaten, and regrowth did not occur after first cutting.
- Cornell has tested Warrior, Lorsban, Pounce and Ambush and found them to be effective. Other products may be effective as well. Always read the label. Choose a product that has a long residual activity. More pest information can be found in the Cornell Guide to Integrated Field Crop Management at www.fieldcrops.org (click on “Cornell Guide”)
Factsheets on Armyworm can be found at:
http://ipm.illinois.edu/fieldcrops/insects/armyworm/
http://counties.cce.cornell.edu/oneida/home%20garden/INSECTS/Insects%20on%20Vegetables/Armyworm.pdf.
