Armyworms In The Lawn: Identification And Prevention

You should know about how armyworms look like, what causes armyworms in grass and preventing them. Armyworm larvae are seen in varying colors from dark greenish-brown to black. They feed almost all the time, but their most active times are early morning and late evening. Time your treatment at the time of activity for maximum results. There are various highly effective controls available to kill armyworms by contact and protect your lawn for up to three months.

What Do Armyworms Look Like?

Armyworm heads may vary in color, but they have a peculiar inverted “Y” mark. On each side of their body, there are long, pale white, dark brown and orange stripes along the length of the abdomen. Mature larvae are about 1 ½ inches long. The head capsule is yellowish brown with a brown network of veins that gives it a sprinkled appearance. Their front wings are colored dark gray with light and dark dots and their hind wings are pale gray-white. The small white dot in the center of each forewing is a distinctive feature to identify the armyworm moth.

What Causes Armyworms in Grass?

While the exact cause is unknown, there are various theories that all oppose each other. One theory says that cool springs and summers with raised moisture levels are the suitable living conditions for armyworms. Another theory is that the natural predators of the armyworm such as wasps and flies, that do not prefer cool and wet weather, are less active for this reason enabling a greater armyworm population to exist.

Armyworms exist every year, although the population can increase during a certain year because of different causes. This population explosion occurs infrequently and without any signs and can every year or be spaced apart by 10-15 years.

While armyworms appear similar to grubs, the standard grub control application is not effective on armyworms. The best prevention is commercial-grade pesticide applications. These should be applied many times throughout the year to help prevent invasions. 

Why Do I Need To Treat My Lawn For Armyworms?

An armyworm infestation can be responsible for  great damage to your lawn if not treated rapidly. You need to get rid of armyworms before these damaging pests destroy your yard as they invade uncontrollably consuming blades of grass as they go. 

Fall armyworms cause the most damage to home landscapes. Other varieties include yellowstriped, beet and the true armyworm. Armyworms aren’t choosy eaters and can attack several kinds of plants as they migrate in search of edible vegetation. With warm-season turfgrasses such as Fescue and Bermuda, they can also attack agricultural crops. As they feed, larvae leave brown spots on the lawn. 

What Damage Do Armyworms Cause?

The armyworm usually goes unnoticed until the damage has been done. One of the first signs of an armyworm infestation is that your lawn will look as though it has been run over with a steamroller. The grass will get discolored and will lay completely flat. It is very easy for an army of armyworms to damage a complete lawn or field within a few days.

As the armyworm feeds, they create brown patches in the lawn that seem to be heat, drought, or chemical stress. These brown areas typically first appear along the perimeter then in the center of the lawns. When observed closely, the plant leaves along the perimeter may appear to be torn or chewed, while the leaves at the center will appear to be cut-off right at the surface.

What are the Best Ways to Get Rid of Armyworms?

Follow these steps to get rid of armyworms in your lawn:

1. Identify Armyworm larvae

The armyworm larvae, or caterpillars are most easily identified by the yellow, green, brown, or reddish stripes that span the length of their body. If you observe closely, the front of their head also has a distinct, inverted “Y” mark. A full-grown larva is 1-1/2 to 2 inches long.

Armyworm activity mostly happens in summer and early fall. The first indication of an armyworm problem is patches of brown grass. On further examination, you will observe the edges of the grass blades look chewed and torned. If you have seen many armyworms or notice destruction to your lawn or garden, it’s time to treat.

2. Remove armyworms from plants by hand and drop them into a bucket of soapy water

Armyworms often hide during the day, but if you see them, it’s best to get rid of them. Manually removing them from your lawn or garden might be enough to bring a small infestation under control. Pick off the armyworm from the plant by hand and then drop it into a bucket of soapy water—liquid dish soap is best. The armyworms will die in soapy water.

3. Spray infested plants with neem oil or other natural insecticide

As armyworms feed on the surface, a spray insecticide is an excellent choice. Chemical and granule pesticides also can be helpful.

No matter what type you choose, it’s best to choose a nontoxic armyworm insecticide that won’t harm beneficial insects. It is good to keep natural armyworm predators around to keep future populations under control. 

4. Treat during early morning or late evening 

Armyworm larvae are most active during the early morning and late evening. Whether you are manually removing the larvae or using an insecticide, it’s best to do it during their active feeding times.

Armyworms reproduce quickly and your lawn can have an infestation of multiple generations of armyworms in a year. Therefore, it’s essential to check for indications of armyworms frequently and treat problems as they arise. 

5. Keep the lawn mowed to a reasonable height and keep grassy weeds at bay

In several areas, natural predators can help keep armyworms away. Strive to make your lawn or garden a better environment for natural larvae predators, such as birds and beneficial insects like rove beetles, ground beetles, and ladybugs.

Long grass and grassy weeds can allure adult armyworms. A lawn with proper maintenance creates a less fascinating environment for the adult moths to lay their eggs. Keeping grasses short and cleaning fallen debris also uncovers armyworm hiding spots, so natural predators can kill existing bugs. Keeping a healthy yard will also help your grass or plants recover in the case of an insignificant armyworm infestation.

What Products Can Be Used To Kill The Armyworms?

Bacillus thuringiensis (B.t.) products can control minor armyworm infestations without harming beneficial insects. Re-treating is recommended because B.t. residue remains on turf for less than two days. Other insecticide options for armyworms in lawns can contain carbaryl, bifenthrin and permethrin.

There are many lawn care products available to kill armyworms in your lawn. Applications of Garden Dust or OMRI-listed Monterey Garden Insect Spray will kill caterpillars. Also, Garden-tech brand offers many highly effective controls to kill armyworms by contact and provide protection for up to three months. Sevin® Insect Killer Granules treat your whole lawn to reach armyworm stages above and below ground.

How To Get Your Lawn Back After Armyworms

After treating armyworms and getting rid of your lawn from the infestation you need to give your lawn a boost. Here are some lawn care tips that will help you get back your lawn. 

1. Apply a fertilizer to enable new leaf growth. This is specifically essential prior to the winter months when the lawn plants will go into their dormant phase.
2. Make sure you water deeply (applying around 1 inch) once a week and limit mowing. The attack of the armyworms has caused your lawn plants to go into shock, so caring a little now will allow it to recover and repair.
3. Unfortunately, armyworms are notorious to return, moving from neighbor to neighbor and feeding on their healthy lawns. 

Eden hopes that now you have enough information about armyworms. Key to prevent armyworm infestation is maintaining a healthy lawn. Eden is here to help you if you have any questions about diagnosis or treatment.