What Kind of Webworm Pests Are Ruining My Lawn?

A lot of pest control services or lawn care companies will talk about webworm damage. However, calling their services “webworm” control is too simple and doesn’t describe the actual issue your lawn is facing. There are multiple different kinds of webworms that feed on different parts of your lawn and cause unique kinds of damage. In the College Station area, the two most common webworms that cause lawn damage are sod webworms and fall army webworms (or fall armyworms). If you want to look into a pest control service or to try and treat your lawn yourself, it’s important to tell the difference and know the type of webworm that is on your lawn to properly treat the issue.

What Sod Webworms Look Like

Image Source: Texas A&M Agrilife Extension

Sod webworm larvae grow a half-inch to three-quarters of an inch long and are usually a tan or gray color. They have dark spots that run along their slender bodies and are typically segmented along the head and body. The heads are typically darker than the rest of the body. When they grow into moths, the wing color will be white or tan and generally paler than the larvae. They may, however, have faint markings or patterns along their wings.

Image Source: Texas A&M Agrilife Extension

Sod Webworm Behavior

The moths of a sod webworm begin the growth cycle by laying their eggs on your lawn. The larvae build silk-lined tunnels in the thatch layer of your lawn or the upper portion of soil that allow for them to travel across your lawn with a layer of protection. As they feed, they leave droppings called frass throughout the lawn. When the larvae mature, they become moths that continue the cycle across your lawn. 

Sod webworms start their activity during the early spring and are usually active until October or November as the weather permits. Mid-summer is when they are most active when it comes to feeding and breeding. They can have multiple generations of larvae within a growing season, which means you can have a reinfestation even after initial treatment. Webworms love to feed when it is hot and dry and target lawns with already stressed or poorly treated grass.

What Fall Armyworms Look Like

Image Source: Texas A&M Agrilife Extension

Fall armyworm larvae, which are generally called caterpillars, are longer than sod webworm larvae and can grow up to an inch and a half long. They are often greener, but their hue can range from light green to brown or gray. The heads make an inverted “Y” shape that is distinct from other worm or grub pests. While the worms themselves are larger, the adult moths are smaller than sod webworm moths with a wingspan ranging from three-quarters of an inch to one inch long. Their wings are a darker brown or gray but often also have faint markings.

Image Source: University of Florida

Fall Armyworm Behavior

The “army” part of their name comes from how they eat your lawn’s turf. The caterpillars have a marching-like formation and will uniformly eat at your entire lawn until it is destroyed. They also are known as caterpillars to travel long distances throughout the neighborhood. At night, because of their size, you may be able to see them move across the lawn if you look closely enough. You are most likely to see evidence of their feedings during the morning or early afternoon.

They are most active during the midsummer to early fall, which is also usually when they start the feeding and reproduction process. If we receive a lot of rain in September, you can bet that there will be armyworm problems, especially in Bermuda lawns. They thrive in the warm climate of the Southern United States during warm summers and mild autumns. Not only do they reproduce quickly, but both eggs and larvae can overwinter within the thatch layer or soil of your lawn, allowing the feeding process to resume quickly when conditions become ideal again.

Similarities Between Sod Webworms and Fall Armyworms

While these webworms look very different, there are some similarities between their behavior and actions that affect how you can try to control them. The larvae and caterpillars of both webworm species grow into small, whitish moths that fly in a zigzag pattern when disturbed on the lawn. Seeing multiple of these moths around your property is a good sign that webworms are the root of lawn damage. Another sign of either species of webworms is frass, which are droppings left behind by these bugs that may be noticeable on your lawn. These droppings vary in location and size based on the species, but for either, small brown or green droppings are a common indicator of their presence on your lawn.

The way that the webworms eat your lawn is incredibly different, but their behavior when they’re actively feeding is nearly identical. Both species are nocturnal, feeding during the night. This means that for both it’s best to apply pesticide or chemical treatment during the late afternoon so that the product doesn’t evaporate but is still consumed by the webworms. When it comes to their feeding, the two webworm types will chew on your grass blades. Even though the look of this differs wildly between species, this means applying the product to grass is effective for both species.

If you notice issues in the late summer or early fall, this could be either variant because they are both active at that time. The pair favor a warmer and dryer climate in Southern states like Texas. If conditions stay similar into October and November, they will both stick around and continue to feed after their typical season ends. Both species also can have multiple generations within one season, so it’s possible that problems can persist after treatment. For both sod webworms and fall army worms, it’s very common for reinfestation to happen.

Soapy Water Treatment to Identify Webworms

One method that can be used to flush out both kinds of webworms is the soapy water method. Mixing a small amount of dish soap and water and pouring the mixture over an affected area could bring the webworms up out of the thatch layer or soil to examine. Because both webworms look very different, this is a way that can help to identify either species. For a bit more information, this article also goes into the process when it comes to flushing out chinch bugs.

Signs of Sod Webworm Damage

The major difference between a sod webworm and a fall army webworm infestation lies in the parts of the lawn that they target. This is the main way to tell apart their damage besides isolating the larvae and examining them. 

Image Source: Michigan State University

Sod webworms only eat at the grass blades of your lawn. The kinds of turf that they most often target to feed on is Bermuda, St Augustine, and Kentucky bluegrass. When eating, they eat the grass at or close to the soil surface and chew to the soil line, which quickly turns grass blades brown. The damage looks like irregular brown patches of grass that can quickly grow and merge together. Grass left behind is short and damaged.

While sod webworms eat most of the grass blade, they don’t touch the roots of your grass. This results in noticeable differences compared to other lawn pests that leave your lawn with brown patches. For one, the feeding pattern results in a scalped or scorched look to the remaining grass blades. Also, only targeting the top part of grass means that it will affect the feel of your lawn differently. While grass will be easy to individually pull up, it cannot be uprooted. Unlike with grubs, it will not feel spongy underfoot and it will be difficult to roll up portions of turf.

It may be possible to see their silk tunnels within the thatch layer or soil if you look closely enough. There also might be evidence through droppings during the day. Sod webworm frass is usually small and fine, the size of a grain of sand. This is noticeable across the lawn as dust or powder either on the surface or in the thatch layer. It will be most noticeable around the affected areas.

Signs of Fall Armyworm Damage

The signs of fall armyworms and the location of damage are very different. Fall armyworm frass is longer and often more noticeable than sod webworm frass. It can measure one-eighth to even one-fourth of an inch long. Instead of a powder, the frass is more granular and is usually found in piles or clumps in specific places on your lawn.

Image Source: Texas A&M Agrilife Extension

Damage from these webworms is not confined to just the blades of grass. It’s not even confined to the grass itself. Fall armyworms are not picky when it comes to what they target on your lawn, and will eat at flowers, stems, plant crowns, and leaves of all sorts. They often do damage not just to your lawn, but to any surrounding landscaping or gardening. Their eating creates an empty, ghost-like appearance for leaves.

Their eating starts at the top and works its way down, which at first can create a similar look of damage to sod webworms, due to how the grass looks brown and ragged. However, brown patches are much larger and spread much more quickly. Large infestations can strip your lawn bare in days, with little to no grass blades remaining. Any remaining grass blades will look thin and ragged. These patches are also more uniform in appearance. 

While they target several parts of your lawn and landscaping, they target warm-season grasses in particular. This means that Bermuda or St. Augustine grasses can be targeted by either species of webworms, but instead of Kentucky bluegrass fall army webworms will prefer to eat Zoysia grass. If you know the type of grass that makes up your turf, you may be able to use this info to figure out which webworm would be most likely to target your lawn.

Professional Pest Control for Webworms

With both species of webworms, they are very mobile and spread so quickly that reinfestation is common. It’s easy for moths that weren’t on your lawn to fly over and lay new eggs, or for treatment to avoid targeting a new generation that’s developing on your lawn. If you want to look into identifying what pest is doing damage to your lawn, are curious about treatment options, or want to reinforce your lawn with fertilizer to keep it strong and resilient against webworms, look into our services. Our team has years of experience across the College Station and Bryan, Texas areas and is happy to lend a hand with figuring out the type of webworms on your lawn. Contact us today for a pest control services consultation.