LC Extension: Fall armyworm infestations trouble local farmers and homeowners

Fall armyworm larvae can be identified by the presence of an “inverted y” on its head and black dots along its abdomen. The larvae cause damage to crops and lawns by eating foilage, according to the Lawrence County Extension Office. 

A larval pest native to the western hemisphere from the United States to Argentina is causing a ruckus among north Alabama farmers this time of year, according to a release from the Lawrence County Extension Office.

“Fall armyworms have arrived in Northwest Alabama,” Extension Coordinator Donna Shanklin with the Lawrence County Office reported.

Shanklin said Regional Extension Agent Paul Vining, with an Animal Sciences and Forages division, has been overwhelmed by the number of calls he has received from hay producers who are trying to manage the pest. 

Similarly, Regional Extension Agent Tim Crow, with a Home Grounds division, has been “inundated with calls from homeowners with concerns about their turf,” Shanklin said. 

She said armyworm infestations may be controlled with pesticides, but the age of the worm may help exterminators determine which insecticide will be most effective. 

“Two types of insecticides are recommended for fall armyworm control—insect growth regulator (IGR) insecticides and pyrethroid insecticides,” Shanklin said in the release. “IGR insecticides inhibit the pest’s growth cycle and typically work well to control small fall armyworms. These insecticides tend to be more expensive in comparison to the pyrethroid insecticides.”

She said pyrethroid insecticides, which kill quickly upon contact, can provide control of small and medium sized fall armyworms. 

Because pyrethroid products are classified as restricted use pesticides, users are required to obtain a pesticide applicator license to apply the product.

“Remember to always read and follow the directions described on the insecticide label and ensure that the product is intended for use where you are planning to use it (pasture or lawn). The pesticide label is the law,” Shanklin added. 

She said fall armyworm larvae can be identified by the presence of an “inverted Y” on the head and four black dots on the end of the abdomen. 

The larvae cause damage by eating foliage; young larvae feed on leaf tissue from one side, leaving a kind of “windowpane” in their wake, according to Shanklin. “By the second or third instar, larvae begin to make holes in leaves, and eat from the edge of the leaves inward,” she said. 

For an in-depth discussion of fall armyworm identification and control, visit the ANR-1019 Management of Fall Armyworm in Pastures and Hayfields website at https://www.aces.edu/blog/topics/farming/management-of-fall-armyworm-in-pastures-and-hayfields/, or the ANR-0172 Controlling Fall Armyworms on Lawns and Turf website at  https://www.aces.edu/blog/topics/lawn-garden/controlling-fall-armyworms-on-lawns-and-turf/. 

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