If you wake up one morning to find that your emerald green lawn is suddenly a dusty brown, you may have an army of armyworms (or another common caterpillar) marching through your lawn. Thankfully, how to get rid of these lawn caterpillars is not rocket science, and most treatments are DIY friendly, even for novices.
- What is a lawn caterpillar?
- Signs you may have lawn caterpillars
- How to test for lawn caterpillars
- How to get rid of lawn caterpillars
- How to prevent lawn caterpillars
- Common lawn caterpillars
- Fall armyworms
- Fiery skippers
- Striped grass loopers
- Tropical sod webworms
- FAQ about lawn caterpillars
What is a lawn caterpillar?
A lawn caterpillar is a moth in its second, or larval, stage of life.
Remember learning about butterfly metamorphosis in school? Lawn caterpillars follow the same life cycle:
Once the caterpillars hatch from their eggs, these small larvae start to eat. You’ve heard of a hungry caterpillar, right? Eating is the raison d’ȇtre of a caterpillar. They eat, molt, eat, molt, and so on until they are ready to pupate, form the chrysalis, and emerge as a moth.
There are a few species of caterpillar you’re likely to find in your lawn:
Signs you may have lawn caterpillars
Lawn caterpillars can turn large swaths of green lawn into brown patches of wasteland in as little as one to two days. Such a quick turn from green to brown will usually indicate a large population of these worms in your lawn. In these cases, you should be able to see them in the grass as you walk across the lawn.
Secondly, notice how fast the lawn declines. If caterpillars are on the job, the lawn (or a part of it) will be consumed quickly, even if you have a lighter infestation. Diseases take longer to develop.
A third way to diagnose the problem is to look at the grass blades. Caterpillars chomp and chew a leaf on either side of the blade’s center vein. You’ll see half-moon-shaped pieces of missing grass leaf on each blade. Other insects pierce and bite, creating small holes instead.
Finally, as you inspect the blades, look for the caterpillars on top of the soil. Some curl into a C-shape; some don’t. Webs and green or brown droppings are other clear signs.
How to test for lawn caterpillars
If you want to be sure you have caterpillars, there’s an easy way to test for that. Do what’s known as a drench test.
Here’s how to do a drench test in your lawn:
- Mark 1 square yard of space in the lawn.
- Fill a bucket with 2 gallons of water. Add 3-4 tablespoons of dish soap.
- Apply the soapy water mixture to the area.
- Wait 10 minutes. If any caterpillars come to the surface, count how many.
- Five or more caterpillars mean you may want to consider treatment options.
How to get rid of lawn caterpillars
So, you’ve marched through your lawn, done the drench test, and confirmed caterpillars are the culprit. How do you get rid of these marching munchers?
Note: Once caterpillars form a pupa, treatments become unnecessary since they’re no longer eating your lawn.
Here are a few simple ways to get rid of caterpillars in your lawn:
Before we get into treatment methods, know that unless you have large numbers of caterpillars in your lawn, pest control treatment may not be needed. However, if you’re concerned, consider the options below to put your mind at ease.
Natural control of caterpillars:
- Bacillus thuringiensis, or Bt for short, is a bacterium that will cause the caterpillar to stop eating. It then dies in a few days. Even better, Bt won’t harm beneficial insects in the lawn. Most products are certified for organic gardening. Look for the OMRI (Organic Materials Review Institute) label to be sure. Bt works best on young larvae. Apply in the early evening when they emerge from their daytime slumber and start to eat.
- Spinosad is another active ingredient that can be used to control caterpillars. Some of these products are OMRI-certified; some may not be. Check the label.
- Parasitic nematodes are recommended as a biological control for fiery skippers.
- If it’s a small infestation, you can hand-pick the caterpillars and drown them in a cup of warm, soapy water or rely on other wildlife to eat them. In one study from 1984, 60%-90% of fall armyworm pupae were eaten by local wildlife.
Chemical control of caterpillars:
- There are at least 10 chemicals that are registered for controlling caterpillars in lawns. Look online or at your local home improvement store for one that suits the breadth of your problem and preferred means of application. Or, check out this chart from the University of Florida.
Remember that when you apply a pesticide to the lawn, you may affect populations of beneficial animals as well as those that eat your lawn. Caterpillars are an important food source for other animals. Some of the wildlife that eat caterpillars include:
- Ground beetles
- Parasitic flies
Not only will these animals have less food, but the chemical residues can be harmful to them and to the all-important pollinators, as well.
Final tip: Whether you treat your lawn or let nature take its course (for small, localized damage), destroy your grass clippings after you mow. This may help reduce the number of eggs on your lawn.
How to apply caterpillar control products: If you have a small area, use a spot treatment spray or granules in that area. For larger infestations, get out a spreader and apply granules throughout the affected area. Or use a sprayer to apply an organic or chemical solution.
How to prevent lawn caterpillars
If you’ve had problems with lawn caterpillars in the past, there are things you can do to prevent the likelihood of another infestation.
Maintain good watering practices
Aim to give your lawn 1 – 1 ½ inches of water (including rainfall) each week. If it doesn’t rain, try to water the lawn only once per week. (Deep and infrequent is the general rule.) If you have sandy soil, two to three times per week is recommended (again, for a total of 1 – 1 ½ inches per week). Remember, excessive water and fertilizer lead to high levels of thatch, which creates a cozy home for insects.
If you’ve followed a fertilizer routine and see caterpillars in the lawn, cut back to twice per year, and use a complete, slow-release fertilizer. Quick-release nitrogen causes too much tender top growth, which caterpillars love.
The problem with insecticides is that they also kill the good bugs that can help control unwanted caterpillars in your lawn. Ground beetles, earwigs, spiders, wasps, and parasitic flies are your friends if you have caterpillars.
Good lawn care is essential
Homeowners concerned about their lawn shouldn’t underestimate the positive effects of good, consistent lawn care on the health of their turfgrass:
- Do you have the right grass planted for your lawn and climate?
- If you have compacted soils, aerate annually.
- If your grass feels spongy under your feet, it’s time to dethatch. A tall layer of thatch creates a cozy home for many unwanted insects.
- Fertilize appropriately — too much is too much.
- Mow often so you remove only one-third of the blade per mow.
Common lawn caterpillars
Here are a few common lawn caterpillars that like to munch on crispy, green grass.
- Identification: Brown with faint stripes
- Which grass types do cutworms eat?
- Identification: Brown with stripes along the sides
- Which grass types do fall armyworms eat?
Armyworms love common lawn grasses like bermudagrass and several weeds, including crabgrass, bentgrass, Johnson grass, and others. Unfortunately, though, fall armyworms will eat almost any turfgrass.
For more tips, see “How to Get Rid of Armyworms.”
- Identification: Brown with dark brown stripes
- Which grass types do fiery skippers eat?
Fiery skippers eat common lawn grasses including bermudagrass, broadleaf carpetgrass, hairy crabgrass, Kentucky bluegrass, and St. Augustinegrass.
Striped grass loopers
- Identification: Range from brown to green
- Which grass types do grass loopers eat?
Grass loopers are a problem in bahiagrass pastures but will eat almost any grass.
Tropical sod webworms
- Identification: Translucent, light brown; if they’ve just had a (grass) meal, you can see the digested green matter along the middle.
- Which grass types do tropical sod webworms eat?
Tropical sod webworms like to munch on all common warm-season grasses as well as the cool-season creeping bentgrass. Some cultivars of St. Augustine and Zoysia have shown resistance, so look into this if you’re starting a new lawn in an area with caterpillar problems.
FAQ about lawn caterpillars
These lawn pests not only feast on your prized lawn grass; they’ll also feast on weeds, such as crabgrass.
From spring through fall. However, in coastal areas or in South Florida, they can be active year-round.
Most lawn caterpillars eat overnight, but some, like the fall armyworm, also may eat during the day. If you look for caterpillars during the day, you can find most caterpillars on top of the soil, resting. Push the grass aside and look at the soil surface to find them. Or, go out after dark with your flashlight.
The short answer is “yes.” Once the caterpillars stop feeding, the grass will have an opportunity to recover. How long it takes to recover depends on the size of your infestation and the health of your grass and soil. Follow the general lawn care tips listed above to help your grass regain top form as soon as possible.
If lawn caterpillars have become more than you can handle, contact one of our local Lawn Love lawn care pros. They’ll give your caterpillars their marching orders and restore your lawn.