Riding the wave of a fall armyworm invasion
Yikes! A golf course invasion of fall armyworm. Through large swaths of the Midwest, fall armyworm has invaded and damaged turf, especially golf course turf. Fall armyworm is a persistent pest in the southern United States, but in the northern region it is normally a sporadic pest. That changed this year.
Photograph 1. Fall armyworm damage to high cut turf. The damaged turf is primarily creeping bentgrass in this instance.
Photograph 1a: Fall armyworm damage to a golf course rough. Symptoms often look like drought symptoms
Considered a tropical pest, the fall armyworm has a restricted overwintering area that reaches from south Florida along the gulf coast to southern Texas. Fall armyworm overwinter as pupae. As the adults (moths) emerge from the pupal cases, they start their migration northward from spring through summer. This summer, the moths have hitched a ride on the jet stream and the back of storms originating in the southwestern and southern United States to northern parts of the United States.
Photograph 2. Damage symptoms due to fall armyworm. The picture was taken the fourth week of August in central Ohio.
Figure 2a. Devastating damage caused to this homelawn by fall armyworm. The turf was devoured by the caterpillars crawling (marching) across the lawn.
Female moths start laying eggs in late summer (July) in clusters. One moth can lay over 1,000 eggs. These egg clusters can be observed on vegetation and surface structures like posts, signs or even golf course flags. The eggs can hatch within 2 to 10 days. The caterpillars emerge and drop to the ground. Fall armyworm caterpillars are unique in that they can feed during the day and at night. The fall armyworm most active feeding is late in the evening and early in the morning.
Photograph 3. The larvae can range in color from olive green (shown here) to light tan to black.
The fall armyworm gets its name in that the caterpillars crawl and feed on the turf shoots appearing like an “army” crossing the turf. What is striking is the shear number of caterpillars present.
In the northern United States, one generation occurs usually at this time when fully grown the armyworm is about 1.5 inches long. It ranges in color from olive green to light tan, to nearly black, typically with light stripes that run the length of the body. An inverted "Y" is present on the front of the head of the caterpillar.
Photograph 4. Fall armyworm caterpillar has a distinct "Y" shape on its forehead. If you look closely you can make the "y" out.
After the caterpillars feed for 2 to 3 weeks, they will move downward in the soil to pupate. Within two weeks a new population of months will emerge. In the southern United States multiple generations can emerge, while in the northern United States the number of generations - as mentioned previously - is limited to one.
Photograph 5. A darker colored fall armyworm.
Fall armyworm can be controlled with insecticides like Acelepyrn®. For more information on control see the article by Matt Geise entitled, Prevent Fall Armyworm Damage on Golf Courses.
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: