Texas A&M AgriLife Extension: Armyworms

According to Texas A&M AgriLife Extension, armyworms are able to lay up to 2,000 eggs, which can hatch in as little as two days.

Experts say that while the area has been dry lately, a large amount of rain in the Brazos Valley could bring a repeat of last year’s armyworm invasion.

These seemingly harmless little moth caterpillars can cause significant damage to plants across the Lone Star State. With the insects’ feeding season approaching, lawncare and crop specialists advise landowners to prepare for a potential wormy war.

Last fall, armyworms marched across the Brazos Valley in full force after heavy summer rainfall brought out more of the small caterpillars than usual,

“If we start getting some big rainstorms, we’ll get armyworms coming in from the woods, wherever they can lay their eggs under leaves,” said Dakota Smith, supervisor with Bryan-based landscaping business The Ground Crew. “... I normally see them at houses backed up to a wooded area, where they hide.”

Smith said he doesn’t often see armyworms on bushes or trees. They particularly enjoy grass, especially Bermuda grass.

“They will munch the grass till it’s dead,” Smith said. “But Bermuda grass will come back from that.”

Smith suggested lawn owners act preemptively by purchasing a systematic insecticide, which will affect the bugs from within the plants themselves. He noted the poison, when applied in the recommended dosage, is enough to kill a tiny caterpillar but should not cause harm to people or pets. Region-specific insecticides can be purchased locally at some landscape supply stores.

While a front yard grass buffet might be annoying for a homeowner to deal with, armyworms’ appetite can be even more devastating for farmers growing crops. In addition to Bermuda grass, armyworms are known to feast on rye grass, hay, sorghum, corn and wheat. According to a press release from the Texas A&M AgriLife Extension, armyworms are able to lay up to 2,000 eggs, which can hatch in as little as two days.

“They can move across a field and move a lot of forage overnight,” said AgriLife Extension forage specialist Vanessa Corriher-Olson. “... They could damage a stand of forage in a pasture or hay meadow overnight.”

Whether a crop will be killed off completely or only damaged, Corriher-Olson said, often depends on the plant’s age. Young seedlings, such as rye grass seedlings planted in October, are most vulnerable to being completely destroyed.

In an AgriLife press release, Corriher-Olson predicts that armyworms will emerge in large numbers should an area see rainfall. She, like Smith, advised that precautions be taken, stressing that it is important for crop producers to have pesticides ready and waiting.

The press release specifies that producers should act once armyworms are seen at a consistency of three or more caterpillars per square foot.

“Diligent scouting is important if you want to preserve a last cutting or stockpiled forages meant for winter,” Corriher-Olson stated in the release. “But producers should also be mindful that armyworms will feed on winter forages like small grains and rye grass. They prefer high-quality forages, so going into fall they will choose seedlings over Bermuda grass.”

At this point Smith has not received any calls about armyworms for the fall 2019 season, nor has Corriher-Olson heard any reports from the agricultural side. If rain does bring in larvae, the bugs could stick around through multiple generations until the first frost.

For more information on fighting armyworms, visit foragefax.tamu.edu.

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