SAN ANTONIO – Texas has seen a considerable amount of rain, coupled with cooler-than-usual temperatures this summer but that has left conditions ideal for an infestation of armyworm caterpillars, also known as armyworms.
“I spent all of Friday taking calls on armyworms. The entire day,” said Texas A&M AgriLife Extension forage specialist Vanessa Corriher-Olson said. “So, it is an issue... it’s hard to imagine they are not everywhere.”
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These caterpillars are the larval form of a moth that migrates north in the spring and summer months to lay eggs and according to retired A&M AgriLife Extension entomologist Allen Knutson, armyworm moths can lay up to 2,000 eggs that will hatch in just 2-3 days.
They get their name from a Latin word, frugiperda, which means lost fruit - an homage to the armyworm’s capability to damage and destroy numerous crops, according to the South African National Biodiversity Institute.
Armyworms are green and typically have brown and black coloring and an identifiable inverted “Y” on their head, according to the AgriLife Extension. When they mature, armyworms can grow up to one inch in length.
The pests are picky eaters and are known to consume Bermuda grass, sorghum, corn, wheat, ryegrass and many other crops throughout Texas. They also prefer high-quality, fertilized crops and forage that are typically found in fields that are maintained for hay production.
“Armyworms are not a ‘spray once and they won’t be a problem’ kind of thing. This could be a two-, three- or four-spray situation if forage for hay or grazing is valuable to them,” said Corriher-Olson.
She described armyworms as being “extremely destructive, especially when infestations escalate out of control.”
“It’s important to act immediately because if armyworms are left unchecked, they can devastate a forage crop in a matter of hours,” Corriher-Olson said. “I’ve seen entire hay meadows that were consumed overnight.”
AgriLife Extension entomologist Dalton Ludwick estimates that two armyworms per square foot can consume 84 pounds of foliage per acre based on U.S. Department of Agriculture data.
So what should you do if you see armyworms in your yard or garden? The AgriLife Extension specialists say the only way to prevent armyworms is the use of pesticides.
Corriher-Olson recommends insecticides labeled specifically for armyworms that also include pyrethroids but notes that a growth inhibitor is also recommended.
“The pyrethroid only takes care of the ones that are in the field while the growth inhibitor provides a residual effect that will kill new hatches and any caterpillars that migrate into the field,” she said.
While there is not a known shortage of the recommended pesticides, Corriher-Olson suggested having it on hand in an effort to be prepared for when the armyworms are spotted.