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Fall Armyworms

AUBURN UNIVERSITY, Ala. – Fall armyworms are nothing new to Alabama farmers. However, homeowners may not be as familiar with them. Recent numbers indicate that this year’s occurrence of fall armyworm populations is the worst it has been in nearly four decades. There are several management and control items that homeowners can do to keep their lawns off the menu.

Characteristics

Properly identifying a pest is the first step to finding a control option. Luckily, fall armyworms have a few distinct characteristics that make this job easier.

“A fall armyworm’s head has light markings that form an upside-down Y,” said Katelyn Kesheimer, an Alabama Extension entomology specialist. “On the opposite end, they have four black dots that form a square.”

Ideally, it is best to find fall armyworms when they are smaller than ½-inch long. The smaller they are, the easier they are to control.

Scouting

Well-maintained, fertilized lawns are like an all-you-can-eat buffet for fall armyworms. In a flash, they can completely strip a lawn and move on to their next target. That is why homeowners must be quick and efficient with their scouting and control.

How do you scout for fall armyworms? This task is fairly simple—know when and where to look.

“The best way to scout is by kneeling in the grass and looking for the caterpillars,” she said. “I recommend scouting during the cooler parts of the day when fall armyworms will be near the top of the grass blades.”

While not ideal, people can scout during the hot parts of the day. The caterpillars will be down near the soil surface during those times. Kesheimer said homeowners can use a soap flush to draw them out.

“To do a soap flush, mix 1 tablespoon of liquid dishwashing soap in 1 gallon of water,” she said. “Using a watering can, pour the soapy water over a 1- to 2-square-foot area. If present, the larvae, will emerge from the soil or thatch.”

Control

When looking for control products for lawns, note that most product labels will list that they are for control of caterpillar pests, rather than specifically for fall armyworms.

“Granular formulations of pyrethroids are the most used methods of control, but there are some spray formulations available,” Kesheimer said. “When using a granular or a ready-to-spray formulation, no dilution or equipment is required.”

Products containing spinosad or Bacillus thuringiensis (Bt) will control smaller caterpillars without harming beneficial insects. However, Bt will only provide control for one to two days. The recent rains could also affect fall armyworm control, as pyrethroid chemicals stop providing control after a rain event.

More Information

A full list of chemical control options, as well as more information on scouting and control, is available in the Alabama Extension publication Controlling Fall Armyworms on Lawns and Turf.

 

Featured image by Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org

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