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Fast-working armyworms destroy lawns, sports fields

Fall armyworms are a type of moth larvae. They have various color phases, ranging from light to dark brown or green, and they reach a maximum length of 1.5 inches. The body is slightly tapered toward the head. The most distinguishing characteristic of this species is the presence of a prominent, light-colored inverted “Y” on a relatively dark head capsule, although this may not be visible on small larvae. Photo by Marissa Schuh, Michigan State University Extension.

Fall armyworms are a type of moth larvae. They have various color phases, ranging from light to dark brown or green, and they reach a maximum length of 1.5 inches. The body is slightly tapered toward the head. The most distinguishing characteristic of this species is the presence of a prominent, light-colored inverted “Y” on a relatively dark head capsule, although this may not be visible on small larvae. Photo by Marissa Schuh, Michigan State University Extension.

People with lush lawns should keep an eye on them: A recurring pest is here in droves.

Moth larvae, known as fall armyworms, are chomping their way through Shelby and DeSoto counties. They are quite literally taking over your turf. The Mid-South is currently the marching grounds for the armyworm strain that loves a good grassy dinner.

Shelby County Extension Agent Dr. Chris Cooper said, “They’re numerous, so that’s why they’re called armyworms — they travel in packs.”

Look for legions atop blades of Bermuda grass, their favorite meal. But in a pinch, they’ll also dine nicely on Zoysia. And it’s not just residential lawns suffering the onslaught.

Farmers with Bermuda hayfields and other grass crops are also at risk, according to Kenny D. Crenshaw, president of Herbi-Systems Inc. “A Bermuda hayfield, they will munch it to the ground.”

The pest problem has even affected local sports. Bartlett High School canceled a junior varsity soccer match Aug. 22 because of a waterlogged field, but then it became apparent that the varsity soccer field was crawling with fall armyworms. Athletic Director Phil Clark said that personnel from Bartlett-based Herbi-Systems were there and spraying the grass within an hour.

Back on the field later that day, he said there were enough dead armyworms that people’s footsteps crunched.

Despite their lawn care company’s quick response, the school still lost about a third of the varsity field’s grass because of the scope of the pest problem. That was a big letdown, Clark said, because the field was plush and in great condition after good care this summer. He estimated recovery would take at least a couple of weeks.

“It’s a shame but it’s just something we’re going to have to live with,” he said.

After talking with his colleagues, Clark said he’s grateful it wasn’t worse. He learned that armyworms ate most of the outfield at Tipton Rosemark Academy’s baseball field.

Crenshaw said that Herbi-Systems has already gotten several hundred calls about the fall armyworm problem. This year’s infestation is the worst he remembers.

“It seems now that these are eating Bermuda lawns down to the ground—the leaves, but not the harder parts, the stolons,” Crenshaw said.

To homeowners and property managers, it seems like their lawns disappear overnight. Some have suspected chemical spraying because the damage is so rapid and widespread, Cooper said. Big patches of tender green grass leaves are gnawed down to the tough stolons (runners) and appear dead. The good news is that it’s just the appearance of destruction.

“Even though it looks bad, your turf grass will survive it,” Cooper said. “It will just weaken the grass.”

Property owners who have maintained a good soil pH and fertilized their lawns according to a soil test will have hardy grass that can bounce back—especially if it’s Bermuda, he said.

The pests appear annually but this year they are extra plentiful. Cooper attributed this peak to a mild winter, a hot summer and heavy rainfalls over the past couple of weeks.

“You’ll see patches here and patches there in the yard, irregular patterns,” he said. “But I have seen a couple yards this week where the whole yard was just wiped out.”

He knows from firsthand experience with his own property how the fall armyworms seem to appear out of nowhere and wreak havoc. Cooper joked, “They eat my Bermuda but they won’t eat my weeds.”

How to detect them

Fall armyworms are most active in the morning and evening but will eat throughout the day.

Cooper said homeowners can check for the pests by getting down on their knees next to the turf that looks like it’s dying. “You can literally see the worms on the leaf blades of that grass. You’ll see them moving around, walking around and eating.”

For detection purposes, some online sources recommend putting a couple of teaspoons of dishwashing detergent in a gallon of water and pouring it onto a patch of grass. The soap acts like an irritant, and any armyworms that are active in the turf will quickly climb up the grass leaves to escape. (Watch a video about this process online at bit.ly/SoapyFlush.)

But in peak years like this one, such tests aren’t necessary to locate fall armyworms in the MidSouth; a simple look at the grass will reveal them. Crenshaw said armyworms will stand up on the end of a leaf blade, and people will sometimes see them walking over a sidewalk, tree trunk or other places.

“But generally, when you see one armyworm, you’ll have a lot of them,” Crenshaw said. “If you see a dozen or a hundred, it’s going to be armyworms.”

Treatment options

Fall armyworms are actually easy to control with insecticides that are as safe as insecticides can be, Crenshaw said. Today’s products for insect control are much safer than the ones that were around just 20-30 years ago.

Cooper said property owners can safely treat the yards themselves with commonly available insecticides. The bottles can be attached to the end of a garden hose and sprayed on the grass, as long as customers read and follow the label’s instructions. Two common recommendations are for:

  • Spectracide’s Triazicide Insect Killer for Lawns & Landscapes
  • Ortho’s Bug B Gon Insect Killer For Lawns & Gardens

See more options in “Insect Control for Home Lawns” provided by the University of Tennessee Institute of Agriculture at bit.ly/UT-ag-insecticides.

The organic approach is available, but it’s less endorsed than chemical control. Although the “green” approach is popular in many areas of life, Crenshaw is highly skeptical about an organic approach to lawn pest control.

He said he’s a fan of what works and what has been tested. “And all the products we use are tested and approved by the EPA for use on home lawns.”

Cooper also recommends chemical options first, but he said that people who want to try an organic solution anyway have a chance if they catch the fall armyworm problem early enough—when they are very small (less than an inch). One such biological pesticide is Bacillus thuringiensis (or Bt). It is soil-dwelling bacteria that doesn’t harm the beneficial insects and only lasts a couple of days.

“Keep reapplying and hope it doesn’t rain between applications,” he said.

Although cold weather will end the march of fall armyworms naturally, both Crenshaw and Cooper said it’s early enough in the year that another wave of them could hatch. Cooper recommends keeping a weather eye on lawns and treating again in a four-week window if needed, particularly if there’s rainy weather.

It’s important to catch an infestation early and stay on top of the situation to control it easily.
Crenshaw said, “They’re not a big problem here … until they are.”


Written by Carolyn Bahm, Express editor. Contact her at (901) 433-9138 or via email to bartlett.editor@journalinc.com.

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