Sod Webworms: Pest Control for Larvae and Moths

When you spend time outside at night on lawns, the odds are good that you’ve seen a few moths. They might have even flown across your lawn a few times. However, while this may look harmless, it’s possible they might be part of the reason why your lawn has started to have dry, brown patches. Some lawn moths grow from sod webworms, as larvae that eat away at a lawn’s grass for nutrients. If you see moths zigzagging frequently, they might be laying eggs on your lawn that are starting to impact their health. Read on to learn more about sod webworm issues and how you can solve them.

Identifying Sod Webworms

Image Source: Texas A&M Agrilife Extension

A lot of lawn pests can look similar, between grubs and worms and the different kinds of eggs. We’ve already written a whole article about identifying sod webworms and telling them apart from fall army worms (despite the name, they have some key differences). You can read that article by clicking here.

In summary, sod webworms are whitish or greenish-gray caterpillars as larvae with segmented heads and dark spots along their bodies. They will grow into white and tan moths with spots along their weeds. During the larvae stage, the sod webworms will build silk tunnels in the thatch layer of your lawn and eat away at the blades of grass during the night. As they grow into moths, they lay eggs on lawns to continue the cycle. They’re active from the early spring to October or November, depending on the weather, with activity peaking during the middle of summer. This allows them to have multiple generations over their active period and multiply across your lawn in a short amount of time, especially during the long, warm Texas summers.

Sometimes, it’s as simple to find sod webworms as looking at your lawn. You may be able to see their silk tunnels in your thatch layer across your lawn or moths zigzagging around your yard. They also leave frass droppings that will show across your lawn as green pellets. When it comes to lawn damage, sod webworms leave a unique look because they eat the blades of grass, but not the roots. This leaves grass looking scorched and ragged while still being technically “intact”. Grass will start to yellow or brown. If your issues include being able to roll up sod or your lawn being spongy when you walk, this is a sign of a different pest being the root of your issues.

Image Source: Texas A&M Agrilife Extension

Treating Sod Webworm Larvae

If you are sure that the pest causing problems on your lawn is sod webworms, there are a few different ways you could treat them on your own.

Pesticides

There are many liquid insecticides that you can apply directly to your lawn to take care of sod webworms. It’s important to make sure that the kind of insecticide you use won’t have adverse effects on your lawn or surrounding wildlife, so check the active ingredients and make sure to only use as the packaging directs.

Be sure to also check to see if your product is designed to target sod webworm larvae or sod webworm moths. Usually, a product is designed for one stage of the growth cycle, but won’t work on the other. It’s more common to find insecticide treatment for larvae, so try to look into insecticide at the early stages of the cycle. For larvae, pesticides are most effective when sod webworms are small and actively feeding. Apply during the late afternoon or evening to make sure you impact them while they’re active. Depending on when you apply and the strength of your insecticide, you may need to reapply multiple times.

Nematodes

Image Source: Wikipedia

For a natural form of pesticides, nematodes are worth looking into as sod webworm treatment. These organisms will target sod webworms by being eaten and killing off the pests. Bacillus thuringiensis is the specific species that will target sod webworm larvae and break them down. Throughout the season they also disperse through the soil, allowing them to build up and avoid future infestations. These are much safer for the environment and will not target other kinds of beneficial bugs.

Reference the package for the nematode bacteria you buy for instructions on spreading these across your lawn. These only target sod webworm larvae, and work their best while larvae are still small at the beginning of the season. Apply them in the late afternoon or evening, since sod webworms are nocturnal and will feed on nematodes for them to do their work. It’s best to apply them when the soil is moist, and some packages involve spreading them with a mixture of water.

Beneficial Birds

Image Source: Texas Tweeties by Bob Zeller

Beyond nematodes, there are also larger animals that can help to control your sod webworm population. Birds, such as robins, naturally are drawn to eating sod webworms. You may notice an increase in bird presence if you’re having a sod webworm infestation. If this isn’t the case, or you haven’t been swarmed with birds, they can help you to clear out webworms and leave your lawn clear. To encourage the presence of beneficial birds, consider putting up a bird feeder or a birdhouse.

Treating Sod Webworm Moths

Image Source: Texas A&M Agrilife Extension

Other than insecticides that are designed to target sod webworm moths, other common treatments for moths will work for the adult stage of sod webworms. To treat them, consider installing a light trap or a bug zapper. This will draw in moths that come to feed or lay eggs and keep them from becoming an issue. Position these traps over multiple parts of your lawn to make sure that you can always reach them.

Preventing Sod Webworms

If you’re still experiencing issues with sod webworms after treatment, it may be important to consider another application or ramp up treatment measures. Because sod webworms can lay eggs so frequently throughout the year, it’s possible that your treatment didn’t kill them off completely or didn’t target sod webworm eggs.

Even after you treat your lawn, it’s important to look at the overall health of your lawn as a possible factor for reinfestation. Sod webworm reinfestation is common, and their favorite targets are lawns with dry, damaged grass. If your lawn has been damaged seriously by sod webworms, consider reseeding or installing new sod across your lawn with resistant grass types like fescue or ryegrass. Here are some other ways that you can help improve the health of your lawn and deter sod webworms from making your yard their new home.

Thatch Control

Image Source: Texas A&M Agrilife Extension

As noted above, sod webworms travel through and bury into the thatch layer of your lawn. The thatch layer is a layer on your lawn that rests between the base of your grass stems and the soil. It’s made up of living grass stems, dead grass stems, and old leaves and roots woven together. Thatch naturally occurs through your lawn growing and being exposed to the elements, and it’s not necessarily something bad. However, if your thatch layer is growing too thick, it can choke out the growth of your grass or provide the perfect home for sod webworms. Removing this layer can help you draw out sod webworms and force them to be exposed to treatments that will remove them. Dethatching your lawn can be complicated to do by yourself, but if you would like to do it, mow your lawn to half its usual height and take a metal detaching rake to draw up and remove the thatch that is removed.

Good Lawn Health Standards

Besides removing thatch, the best way to prevent sod webworms is to keep your lawn healthy and practice the right standards to keep it thriving. Make sure to keep your grass at the right height for its type, especially if it is Bermuda, St Augustine, or Zoysia, as these are common targets for sod webworms. Generally, most grass types are healthiest at a length of 2 ½ to 3 ½ inches. Long grass might provide shade that deters sod webworm moths, but can also increase thatch buildup.

Drought stress is also a huge green flag for sod webworms, so make sure that even in dry summers your lawn is well-watered. Deep watering also can help grass to recover from sod webworm damage. Generally, the kinds of lawn care that will aid the growth of your lawn will help your lawn to recover and prevent future issues. Core aeration can help your grass to breathe and grow stronger, aiding recovery efforts naturally.

Fertilization for Pest Control

Sometimes, even with proper care and treatment, it can take a while for grass to recover from sod webworm damage and go back to its previous look. In these cases, your lawn might need a boost. Fertilization can make a huge difference across newly planted sod or damaged grass as well. Different fertilizer applications can help with different things, but focusing on fertilizer that promotes root and blade growth to help your lawn’s appearance and health will pay dividends. Make sure that any fertilizer you purchase does  not have excessive nitrogen. This can result in tender, vulnerable growth that is an easy target for sod webworms and other pests.

Pest Control and Fertilization Experts

There are a lot of different steps throughout pest control that you may want help with or even a professional opinion. From identifying lawn pests, to treating sod webworms, to applying fertilizer to help the grass grow back thick and healthy, our team at The Fertilizer Guy can handle the job. We have been providing expert services across the College Station and Bryan, Texas area for years. You can contact us at any time to schedule services or a consultation.