Armyworms are eating lawns overnight: Experts share the best grass treatments

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Protect your lawn from hungry armyworms with these treatments. (Photo: Lowe's)
Protect your lawn from hungry armyworms with these treatments. (Photo: Lowe's)

When you have a lush, green lawn, you want to keep it looking that way. But there's a tiny enemy out there that wants to torpedo your plans. They're called armyworms, and they're eating their way across lawns right now.

Armyworms are a type of caterpillar, Howard Russell, an entomologist at Michigan State University, tells Yahoo Life. "They get their common name 'armyworm' from their marching behavior when very high numbers of them occur," he explains. "They consume their favorite host plants in an area, then march en masse to new areas to find food, consuming nearly every plant in their path."

Armyworms are actually the larval stage of the armyworm moth (i.e., baby moths), Ben Hottel, technical services manager at Orkin, tells Yahoo Life. "You can identify full-grown armyworm larvae by their brownish body, and thin white stripes down the center of their back," he says.

The Midwest in particular is struggling with armyworms right now, Russell says. "[They are] devouring lawns and crops," noting that some counties in Ohio are reporting their worst outbreaks of fall armyworms in 30 years.

Unfortunately, these little critters like to eat. "Armyworms will eat a variety of plants, not just turfgrass," Stephanie Evans, board-certified entomologist and technical education manager for Ehrlich Pest Control, tells Yahoo Life. "They move across a field or lawn like an army, hungrily chomping down the plants in their path. They not only have a voracious appetite, but when the conditions are right — like we are seeing this year — their populations can be huge."

Before you give up and assume your grass and plants are doomed to be consumed by these tiny invaders, know this: There are treatments you can use to get rid of armyworms.

In general, armyworm treatments contain one of the following active ingredients:

  • Spinosad. This is derived from a soil bacteria, Evans explains. "It acts as a neurotoxin that basically excites the caterpillar’s nervous system to the point they become paralyzed and die," she says. "There are various products containing spinosad that are approved for organic use."

  • Bacillus thuringiensis. Also known as Bt, this is a common soil bacteria that will affect insects when they eat it, Evans says. "It gets activated inside of the insect’s gut, and causes it to starve to death," she says. "Bt products will not cause harm to mammals like people and pets, so it is often used not only for caterpillars, but as a mosquito larvicide for treating standing water." Just keep this in mind, per Russell: This really works best on smaller armyworms. "Marching fall armyworms are too big to be controlled by Bt unless you hit them with the bag," he says.

  • Bifenthrin, carbaryl and permethrin. Carbaryl is from a class of chemicals called carbamates. "It’s been around for a while, and you may even recognize its original brand name, Sevin," Evans says. Bifenthrin and permethrin belong to a class of chemicals called pyrethroids. "When using any of these products, you have to read the label," Evans says. "There will be important precautions you must follow to protect not only yourself when applying the product, but the environment as well. The pyrethroids are commonly used in pest control due to their efficacy, but you have to follow the label directions when applying them." This group of pesticides, though, are "effective in controlling fall armyworms" and can help keep them away, Russell says.

Ready to save your lawn? Stock up on these products.

Sevin Insect Killer Lawn Granules

Those armyworms won't know what hit them. (Photo: Lowe's)
Those armyworms won't know what hit them. (Photo: Lowe's)

You can treat a lot of lawn with Sevin Insect Killer Lawn Granules — this 20-pound bag can handle up to 20,000 square feet. Sevin will help protect your lawn from damaging insects like armyworms for up to three months. It also tackles more than 100 other insects, including ants, fleas, tick and grubs. "After one application we were rid of the army worms," a satisfied customer said.

$17 at Lowe's

Spectracide Triazicide for Lawns

This pesticide kills armyworms and other pests on contact. (Photo: Lowe's)
This pesticide kills armyworms and other pests on contact. (Photo: Lowe's)

This fast-acting pesticide takes out more than 100 insects, including armyworms, ants, crickets, fleas and roaches. Spectracide Triazicide is meant to be used when pests first appear or when you notice you have lawn damage. Just apply the granules to the grass and then water your lawn. This 20-pound bag covers up to 25,000 square feet of grass. "I applied insect killer to a 4’x12’ garden bed after all plantings were removed," a happy customer said. "Next morning, I collected 63 grubs that were either dead or dying... . Great stuff. I’ll buy it again next year."

$13 at Lowe's

BioAdvanced Grub Killer Plus

Take out all kinds of grubs at once. (Photo: Lowe's)
Take out all kinds of grubs at once. (Photo: Lowe's)

Got grubs? BioAdvanced Grub Killer Plus kills them within 24 hours. It also takes out armyworms, chinch bugs, crickets, ticks and more. Just sprinkle it on and water your lawn. "My lawn was severely ruined by an infestation of grubs in the later stages. I was in a panic," a fan said, noting that they reached for this grub killer. "Within one to two days, the activity ceased," they said. "After the third day, I began partial renovation and reseeding. It's now about two and a half weeks after the fact, and my lawn is making a full recovery."

$20 at Lowe's

EcoLogic Lawn & Yard Insect Killer

This pesticide is made with a naturally-derived botanical oil. (Photo: Lowe's)
This pesticide is made with a naturally-derived botanical oil. (Photo: Lowe's)

Nervous about using traditional pesticides on your grass? EcoLogic Lawn & Yard Insect Killer uses corn mint oil and geranium to help keep armyworms and other pests away. It's safe for use around kids and pets — just sprinkle on up to 20,000 square feet of your lawn, and water. "The smell is wonderful if you like the natural smell of essential oils. We will continue to use this product for as long as they make it."

$14 at Lowe's

Ortho BugClear for Lawns

Attach your hose and go to work. (Photo: Lowe's)
Attach your hose and go to work. (Photo: Lowe's)

Got a garden hose? That's all you need to get to work with Ortho BugClear for Lawns. This pesticide kills 235 different bugs, including armyworms and ants. It starts to take pests out in minutes and continues to keep them away. Just attach your hose to the bottle and spray away. "I was having a lot of issues with insects...so gave Ortho Bugclear insect killer a try. I noticed within a couple of days that I did not see as many insects around my lawn perimeter of my home," a happy customer said. "I will continue to use Ortho Buglclear to reduce the nuisance of insects while enjoying some quality time outside at home."

$5 at Lowe's

The reviews quoted above reflect the most recent versions at the time of publication.

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