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Fall armyworms are among the most common caterpillar pests of southern lawns.

AUBURN UNIVERSITY, Ala. – Fall armyworms are already making their presence known in Alabama. Usually seen later in the year, mild winter conditions and warm spring temperatures made for early development and emergence of fall armyworms.

“We had a mild winter so, everything is running a few weeks ahead of schedule this year,” said Katelyn Kesheimer, an Alabama Extension entomologist. “Spring temperatures were above average which gives insects an early start on their migrations. This translates to an earlier and longer pest season.”

Fall armyworms are detrimental to pastures and hay fields. Most often the damage they cause seems to appear overnight. It takes about 30 days for a female fall armyworm to develop from an egg to the point where she is ready to lay an egg of her own. Moths lay eggs almost every day. Therefore, all sizes of fall armyworm caterpillars can be found in any given field.

Dry Weather Making Things Difficult

Many areas of Alabama are facing abnormally dry or even moderate drought conditions. This is also playing a role in the presence of fall armyworms.

“Populations are often kept in check by natural enemies,” said Kesheimer, who is also an assistant professor in Auburn University’s department of entomology and plant pathology. “However, during hot, dry weather or drought conditions, natural enemies are less active, leaving fall armyworm populations to survive and even thrive.”

Kesheimer added that the state is currently in a prime time for an outbreak.

“With the recent rain following an extended dry period, it creates favorable conditions for survival, especially of eggs and small larvae.” Kesheimer said. “So, we may see large numbers of worms very soon.”

Scouting for Armyworms

It’s hard to spot fall armyworm damage until after it’s too late. Kesheimer said this is why scouting is so important.

“By the time you see obvious feeding damage or big worms, you’ve likely already lost some yield and control will be difficult,” Kesheimer said. “That’s why getting out there early with a sweep net to scout is the best defense we have against this consistent pest.”

Man using a sweep net scouting for insects.

Image by: Howard F. Schwartz, Colorado State University, Bugwood.org

Kesheimer said producers should keep a sweep net in vehicles at all times. A sweep net is a good, inexpensive way to find fall armyworms when they are small. Most Alabama Extension county offices have a sweep net that you can borrow for scouting. Early morning or evening are the best times to scout for armyworms.

“Try to avoid scouting in the heat of the day. Worms will crawl down into the thatch layer to stay cool and will be more difficult to spot,” Kesheimer said. “If you scout when it’s still cool, you’ll likely catch the armyworms on the grass blades feeding and your counts will be more accurate.”

It is better to be proactive against this pest and seek control early, rather than getting revenge late. If you find armyworms, check to see how many caterpillars are present per square foot. If there are more than two caterpillars per square foot, consider applying an insecticide, cutting the hay or grazing the affected forage.

More Information

For more information on fall armyworms, visit Alabama Extension online or contact your county Extension office.

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