The common armyworm is a frustrating lawn pest that strikes during late summer and early fall. Consuming grasses, tree leaves, and other host plants, these creatures act like an ‘army’ that raze anything in their paths.
An armyworm problem has the potential to completely take over your yard and garden. Failure to address them in the early stages could lead to more serious issues down the road, and the irreparable damage of grass blades.
This article provides a helpful overview of dealing with an armyworm infestation and offers some actionable tips for their treatment, control, and prevention.
Fall armyworms are destructive pests that cause severe damage to lawns in the Southeastern United States.
The term ‘armyworm’ refers to a large number of caterpillar species, including but not limited to:
- True armyworm
- Beet armyworm
- Fall armyworms
While each of these species are slightly different, they share many similar characteristics:
- Larvae are 1 1⁄4 to 1 1⁄2 inches long
- Distinctive inverted ‘Y’ shaped suture on their foreheads
- Brown, light green, or dark green body colors
- A linear white stripe followed by brown stripes (or yellow stripes) on their bodies
- A small moth measuring 1 inch long
- White hind wings (on adults)
- Dark gray or brown forewings (on adults)
If you can identify at least five of the above features on a pest vector, there is a high likelihood of an armyworm infestation around your property.
Like many other types of lawn pests in America, the armyworm has a four-step lifecycle: egg, larvae, pupa, and adult.
- The early growth stage of the armyworm begins with the egg. Armyworms regularly lay eggs on the undersides of leaves and grassy weeds. After one or two weeks, eggs hatch into armyworm larvae.
- Armyworm larvae are the most dangerous portion of the pest’s lifecycle. They begin to eat almost immediately after hatching, and are most active during the early morning and late evening (when temperatures are cooler). Affected plants will show signs of significant damage, including holes in plant leaves, brown grass, and ragged edges on grass blades.
- After 6 instars, the larvae will be ready for the next stage of their lifecycles. Full grown larvae will begin the process of pupation between 14 and 30 days. After forming a dirt and silk cocoon around themselves, larvae have between 7 and 37 days to achieve adulthood. Pupae shells are commonly found underground in the top layer of soil.
- Adult armyworm moths fly about the yard to look for a new nesting place. Within a few weeks, a new generation of armyworms have hatched into the property. The female armyworm moth can lay up to 1,500 eggs during her lifetime, making the management of infestations extremely difficult.
Because of their rate of reproduction, a small armyworm problem can double without warning as pests lay their eggs within tall grasses or shrubs.
Signs of Armyworms in Lawn
If you think or know that armyworms could be overtaking your lawn, keep on the lookout for these signs and symptoms:
- Small caterpillars found feeding on grass
- Large brown patches of grass that are many square feet long
- Eggs or ootheca groups on the undersides of leaves
- Later stages of armyworms, including pupae and adults
- Notice damage around grass blades and other plants
Spotting any of these signs may point towards a potential armyworm infestation. It’s a good idea to start treatments right away, either on your own with DIY products to kill armyworms or with the help of a professional company.
How to Kill Armyworms
The two most popular ways to control armyworms are pesticide use and natural control. Let’s explore each of them and their unique outcomes.
There are a few over the counter pesticides that can help to control the spread of armyworms:
- Bacillus thuringiensis: A fungus that only attacks worms and caterpillars, providing a low-impact solution.
- Methoxyfenozide: Although it’s a more expensive option, this treatment lasts the longest and works the fastest, eliminating embedded infestations with ease.
- Spinosad: This treatment controls foliage-loving worms and their relatives with a cost effective solution.
No matter which pesticide option you choose, it’s a good idea to treat early and often.
Armyworm Natural Treatments
Below are a few ways to get rid of armyworms using natural methods and techniques.
- For less overwhelming armyworm infestations, consider removing and killing worms by hand. Squirt a few tablespoons of dishwashing liquid into a container of water. One by one, pick up and drop armyworms into the bucket of soapy water. The thick liquid will kill them instantly, while also providing a low-impact alternative for your lawn and garden.
- Another great way to naturally kill armyworms is by raking up the underlayers of grass (sometimes called thatch). Remove thatch at least once per month during the active season, and keep a close eye on your lawn during late summer.
- The last and most effective method of killing armyworms naturally is by attracting predator pests. Ground beetles are some of the most effective, although there are many that exist in the natural world. Other natural armyworm predators, including birds and beneficial insects, should be attracted to to yard to reduce serious armyworm numbers. However, bear in mind that it’s not a good idea to attract too many at once (for fear of a secondary infestation).
How to Prevent An Armyworm Infestation
The best method of protection against armyworms is with longstanding prevention. Adding a layer of security around your yard will stop infestations from spreading, while simultaneously killing off potential vectors before they have a chance to breed.
Here’s how to get rid of armyworms before they ever set foot on your property:
- Enact best lawn management practices, including the proper fertilization of grasses and shrubs.
- Water the yard frequently to reduce any stress from drought, which may attract a small group of pests.
- Aerate your lawn at least once per year, opting for professional roll treatments.
- Weed the yard often, taking care to eliminate any large plants with grass-like vegetation.
- Turn off your house lights at night to prevent your property from attracting adult armyworm moths.
If an armyworm infestation has already found its way into your home, you may need to pivot toward different treatment types.
Will my lawn recover from small brown lawn patches?
The good news is that small patches of armyworm damage can and will recover after a short rest period. The bad news is that long-term damages may require a complete re-seeding. It’s a good idea to get your armyworm control methods set in stone before attempting to revive your grass.
What keeps armyworms away from the entire lawn?
Consider utilizing a wide spectrum treatment for all stages of the armyworm’s lifecycle. For a more targeted approach, consider Bacillus thuringiensis. Your entire yard should be treated quickly to avoid second or third generations in later months.
What organic materials kill army worms naturally?
Natural predators are an excellent method way to kick armyworm caterpillars out of your lawn, as well as adult moths that could be looking for a nesting site. Remove thatch frequently, weed often, and perform soapy water ‘treatments’ when necessary.
Neem oil is another natural pesticide that stems from neem leaves. It works by stopping the insects from producing hormones that contribute to them continuing to mate and feed.
Pyrethrin is another natural pesticide that won’t harm other creatures. It consists of dried flowers and paralyzes the armyworms.