How To Get Rid Of Dew Worms

If you’re seeing small mounds of soil and castings on your lawn, you’re likely dealing with dew worms. Learning how to get rid of dew worms can help you restore your grass to a smooth, healthy state. These earthworms are common, but their activity can create a bumpy, messy surface that’s frustrating for any gardener.

Dew worms, often called nightcrawlers, are large earthworms that thrive in healthy soil. They surface at night, pulling organic material into their burrows and leaving behind castings. While they are excellent for soil aeration, their mounds can smother grass, create uneven ground, and provide a haven for weed seeds. This guide offers simple, effective methods to manage their population.

Completely eliminating dew worms is neither practical nor desirable, as they improve soil health. The goal is to manage their surface activity to protect your lawn’s appearance. A combination of cultural practices and targeted treatments works best. Here are the core strategies you can use.

Change Your Watering Schedule

Dew worms need moist soil to breathe through their skin. They come to the surface when the top layer is damp. By adjusting how you water, you can discourage them from venturing up.

Water your lawn deeply but less frequently. This encourages grass roots to grow deeper.
Water in the early morning, not the evening. The surface will dry out during the day, making it less inviting at night.
Allow the top inch of soil to dry out between watering sessions.

Improve Lawn Drainage

Wet, compacted soil is a paradise for dew worms. Improving drainage makes your lawn less hospitable to them. Here’s a few things you can do:

Aerate Your Lawn: Use a core aerator to pull out plugs of soil. This reduces compaction and allows water to drain faster.
Top-Dress with Sand: After aerating, spread a thin layer of sharp sand over the lawn. Sand drains quickly and can make the surface less comfortable for worm activity.
Fix Low Spots: Fill in any areas where water pools to prevent soggy soil.

Adjust Your Mowing Height

Keeping your grass slightly longer helps dry the soil surface faster. The taller blades shade the soil less than very short grass, allowing the sun and wind to dry the thatch layer. Set your mower blade to cut at about 3 inches high. This also promotes stronger grass roots that can better handle worm castings.

Remove Thatch Regularly

Thatch is the layer of dead grass and organic matter between the soil and the green blades. It holds moisture like a sponge, creating the perfect damp environment for dew worms. Dethatching your lawn once a year, preferably in early fall or spring, removes this moist layer and can significantly reduce surface activity.

Use Natural Soil Amendments

Certain natural products can gently encourage worms to move deeper into the soil without harming them or the environment. Apply these in the evening when worms are near the surface.

Mustard Solution: Mix 1/3 cup of dry mustard powder with 4 liters of water. Pour it over a square meter of lawn. The irritation will bring worms to the surface, where you can relocate them to garden beds.
Neem Oil: A diluted neem oil solution can make the top soil layer less appealing. Follow the product’s instructions for lawn application.
Diatomaceous Earth (Food Grade): Sprinkle this fine powder on dry soil. It has a drying effect that worms avoid, though it needs reapplication after rain.

Manual Removal (At Night)

For a small lawn, you can manually reduce the population. This is the most direct method, but it requires some effort.

Wait until after dark with a flashlight and a bucket.
Go out to your lawn and you’ll likely see dew worms on the surface.
Collect them by hand and place them in the bucket.
Relocate them to your vegetable garden or compost bin, where their digging is beneficial.

Maintain Soil pH Balance

Dew worms prefer neutral to slightly acidic soil. Testing your soil’s pH can give you valuable information. If your soil is very neutral, making it more acidic can discourage worms, but this also affects grass health. Aim for a lawn pH of 6.0 to 7.0. If you need to lower pH, applications of sulfur can help, but do this gradually and based on a soil test result to avoid harming your grass.

When to Consider Chemical Controls

Chemical pesticides should be an absolute last resort. They harm the soil ecosystem, killing beneficial organisms along with the worms. In many areas, pesticides for earthworms are not even recommended or legal. The cultural and natural methods listed above are safer and more sustainable for long-term lawn health. Always prioritize health of your soil over a perfectly mound-free lawn.

Prevent Future Problems

Consistent lawn care is the best prevention. A healthy, well-drained lawn with strong grass will have fewer visible problems, even with a healthy worm population below.

Continue with a regular aeration and dethatching schedule.
Remove grass clippings after mowing to reduce excess organic matter on the surface.
Avoid over-fertilizing, especially with organic fertilizers like manure, which can attract more worm activity.

Frequently Asked Questions

Are dew worms bad for my lawn?

Not inherently. Their tunneling aerates the soil and their castings are rich in nutrients. The primary issue is cosmetic—the mounds can smother grass and create lumpy terrain for mowing and walking.

What is the fastest way to remove dew worms?

The manual removal method at night provides immediate results for a small area. For larger lawns, applying a mustard solution will bring them to the surface quickly for collection.

Can I use vinegar to kill dew worms?

While vinegar might harm worms, it is also a non-selective acid that will damage your grass and soil biology. It’s not a recommended or effective solution for lawn care.

Why are there so many dew worms in my yard?

A high population usually indicates healthy, organic-rich soil with good moisture. It often means your soil is in good condition, but the surface conditions are too ideal for their nighttime activity.

Will grub treatment kill dew worms?

Some broad-spectrum insecticide treatments for grubs can also harm earthworms. Always check the product label. If your goal is to preserve soil health, choose grub treatments that specify they are not harmful to earthworms.

Managing dew worms is about balance. By using these simple methods—like changing your watering habits, improving drainage, and using natural amendments—you can reduce their visible impact. Remember, a few worms are a sign of a living soil. The goal isn’t a worm-free lawn, but a lawn where grass and worms coexist without the messy mounds. With a little patience and these effective strategies, you can achieve a smoother, greener lawn that’s still full of life beneath the surface.