Sasha CampbellNot every creature called a “worm” is a true worm. Some are young moths or beetles. Others are tiny worms that live in the soil.
Many worms do no harm to your plants. Before you try to get rid of one, find out what it is and look for signs of damage.
Harmful Worms and Worm-Like Pests in Gardens and Lawns
Here are ten pests that may cause problems in gardens or lawns, along with ways to manage them.
1. Asian Jumping Worms
Asian jumping worms move quickly and twist from side to side when disturbed. They feed near the soil’s surface.
Large numbers can leave the soil looking like coffee grounds and make it harder for plants to grow [1].
How to control them:
Pick up any jumping worms you find and put them in the trash. Do not move soil, mulch, compost, or plants from an affected area to another garden.
Their tiny egg cases can travel in these materials. Hand removal may lower their numbers, but there is no proven treatment that will clear them from a garden [1].
2. Cutworms
Cutworms are caterpillars, not true worms. Some chew through young plant stems near the ground.
You may find a fallen seedling in the morning after a cutworm fed at night [2].
How to control them:
Look around damaged seedlings in the evening. Gently dig near each stem and remove any cutworms you find.
You can also put a cardboard collar around a new seedling. Push it about an inch into the soil, leaving a few inches above ground to protect the stem.
3. Land Flatworms
Land flatworms have soft, flat bodies. Some kinds eat earthworms and other small animals in the soil.
Their effect on a garden depends on the species. Finding one does not always mean you have a serious problem [3].
How to control them:
Check new potted plants before adding them to your garden. If you find an unfamiliar flatworm, take a clear photo to help identify it.
Wear gloves to pick it up, place it in a sealed bag, and freeze the bag before putting it in the trash. Do not chop the flatworm into pieces.
Some kinds can grow a new body from a piece left behind. There is no simple treatment proven to clear land flatworms from a whole garden [3].
4. Armyworms
Armyworms are caterpillars that eat leaves. Some kinds attack garden crops, while others damage lawns and other grasses.
Large caterpillars can eat a great deal in a short time [4].
How to control them:
Check plants often when you first notice chewed leaves. Pick off caterpillars if there are only a few.
For a larger problem, a Bacillus thuringiensis product, often called Bt, may help while they are still small.
Choose a product labeled for caterpillars and for the plants you are treating. Follow the label directions [4].
5. Root-Knot Nematodes
Root-knot nematodes are tiny worms that feed on plant roots. They can cause swollen lumps, called galls, on the roots.
Affected plants may grow slowly or produce less food. Many other problems can also make a plant look weak, so check its roots before blaming nematodes [5].
How to control them:
During a hot, sunny part of the year, you can try soil solarization.
First, water the soil. Then cover it tightly with clear plastic so the sun heats the soil beneath it. How long the plastic must stay in place depends on the weather and your location.
Solarization can lower nematode numbers, but it may not remove them all [5].
Some types of marigolds may also help when grown thickly across the affected bed before you plant the next crop. A few marigolds beside your vegetables are unlikely to protect them [6].
6. Corn Earworms
Corn earworms are caterpillars that feed on corn. They can also damage tomatoes and peppers.
On corn, they often enter an ear near its tip and eat the developing kernels.
How to control them:
Start checking corn when the silk appears. If earworms have caused trouble in past seasons, a Bt product labeled for use on corn may help when applied to fresh silk as directed.
Timing matters. Once a caterpillar is inside the ear, a spray is unlikely to reach it. You can pull back the husk at the tip of a damaged ear and remove the caterpillar by hand [7].
7. Cabbage Worms
Cabbage worms are green caterpillars that eat cabbage, broccoli, kale, and related crops. They leave holes in the leaves.
Check the undersides of leaves, where small caterpillars can be easy to miss [8].
How to control them:
Put a light row cover over your crops when you plant them. Secure the edges so butterflies cannot get underneath to lay eggs.
If you find a few caterpillars, pick them off. A Bt product labeled for these crops can help when the caterpillars are young [8].
8. Sod Webworms
Sod webworms are caterpillars that live in lawns. They eat grass and may leave thin or brown patches.
Brown grass can have many causes, so look for the caterpillars before treating your lawn [9].
How to control them:
Keep the lawn healthy so it can recover from light feeding.
If you confirm that sod webworms are causing damage, a Bt product labeled for lawn use may help while the caterpillars are young. Follow its directions for when and how to apply it [9].
9. Wireworms
Wireworms are the hard, thin larvae of click beetles.
They live in the soil and feed on seeds and underground plant parts. They can make holes in potatoes and damage young plants [10].
How to control them:
If you have had wireworm damage before, check the soil before planting again.
A buried bait trap can help you find out whether wireworms are present. Remove old tubers and dead plants from the bed.
Crop rotation may help over time, but it will not get rid of wireworms at once. Soil that was recently covered in grass or pasture may have more wireworms [10].
10. Grub Worms
Grub worms, also called white grubs, are beetle larvae that live in the soil. Some kinds feed on grass roots and can weaken or kill patches of lawn.
Dig under a damaged patch to check for grubs before treating it. A brown patch alone does not prove they are the cause [11].
How to control them:
A healthy lawn can stand some grub feeding. If grubs are causing serious damage, beneficial nematodes may help.
Choose a product suited to the grub species you have and follow its directions. These living nematodes work best when soil conditions are right, especially when the soil is moist.
You may also see milky spore sold for grub control. The commercial product targets Japanese beetle grubs, but university trials have not found it to be a reliable way to control them [11].
Takeaway
A creature that looks like a worm is not always harmful. Find out what it is and check for damage before taking action.
Picking pests off by hand, protecting young plants, and using a suitable treatment at the right time can help keep damage under control.
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