Fall Army Worm

Will Hudson, UGA Extension Entomologist

August 2, 2010

Description: fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

In late summer, almost every year, caterpillars invade turfgrass throughout the state. The damage to established turf is mostly aesthetic, but newly sodded or sprigged areas can be more severely damaged or even killed. While there are several caterpillars that can damage turfgrass, in late summer most of the problems are from fall
armyworms. Their favorite turf to feed upon is Bermuda grass.

Adult armyworm moths are active at night and females lay
eggs in masses of 50 to several hundred. Eggs hatch in a few days, and the young larvae begin to feed on leaf tissue. Damage from small larvae may at first look like skeletonizing, but as the worms grow, the entire leaf is consumed.

Armyworms are most active early and late in the day, spending the hotter hours down near the soil in the shade. Larvae feed for 2 to 3 weeks before pupating in the soil. Moths emerge 10 – 14 days later. The entire life cycle from egg to adult moth takes about 28 days in the warm weather of August and September. If there is any doubt about whether worms are present, pouring soapy water on the grass (1/2 oz. dishwashing soap/gallon water) will bring them up very quickly.

Control of armyworms and other turf caterpillars is relatively simple once the problem is identified. There are several pesticides from which to choose depending upon the site you are treating. Consult the UGA Pest Management Handbook or your local Extension Agent for recommendations. See the links below for contact information. Read and follow all label directions when using pesticides.

Armyworms are most active late in the day and at night, so pesticide applications should be made as late as practical for best results. It is not necessary to water after application but an application rate of 20 – 25 gallons of solution per acre as a minimum will ensure good coverage. Do notcut grass for 1 –3 days after application.