10 Worst Garden Pests: Proven Fixes for Every Bug

The worst garden pests are aphids, slugs, Japanese beetles, hornworms, squash bugs, cucumber beetles, cabbage caterpillars, spider mites, cutworms, and harlequin bugs. Most home gardeners can handle them without spray. University of Maryland Extension says aphid outbreaks do not always need action, and that pesticides are a last resort.

Start with the gentle fixes. Spray aphids and mites off with water, hand-pick beetles and caterpillars into soapy water, and crush eggs. Cover seedlings with row cover, and put a collar around cutworm targets.

Match the fix to the pest. Slug baits with iron phosphate are the less toxic choice, and a hornworm covered in tiny white cocoons should be left alone.

Save sprays for serious damage that hand-picking hasn’t stopped. Always read the label, because the label is the law, and use only what it allows.

What should you do before you spray anything?

Look first, then act. Turn leaves over, check the base of seedlings, and look again at dusk, since many pests feed at night.

Extension guides call this Integrated Pest Management, or IPM. The idea is to use gentle tools first and chemicals last. UMD says to try the lowest-toxicity option first when you do need a product.

Healthy plants take a hit better than stressed ones. Skip extra nitrogen, water when plants need it, and pull weeds that hide pests. Some herbs also help keep vegetable garden pests down.

How do the 10 worst garden pests compare?

Pest	What you’ll see	Best first fix
Aphids	Clusters of small soft insects, sticky honeydew, curled new leaves	Strong water spray
Slugs and snails	Silvery slime trails, ragged holes in leaf interiors	Night hand-picking, iron phosphate bait
Japanese beetles	Lacy, skeletonized leaves, metallic green beetles	Tap into soapy water
Tomato hornworms	Whole leaves gone, big green caterpillars	Hand-pick
Squash bugs	Yellow spots, wilting vines, egg clusters in a V	Crush eggs, board traps
Cucumber beetles	Chewed seedlings, sudden wilt	Row cover, hand-pick
Cabbage caterpillars	Holes in cabbage-family leaves	Bt on young caterpillars
Spider mites	White stippling, fine webbing	Rinse leaves, then soap
Cutworms	Seedlings cut at the soil line	Collars
Harlequin bugs	Black and red or yellow bugs, white stipples	Crush eggs, row cover

1. Aphids: Rinse them off first

Aphids are small, soft, pear-shaped insects, about 1/16 to 1/8 inch long. UMD says they come in green, yellow, pink, red, blue-black, and gray. A pair of tailpipe-like cornicles on the rear is the key sign.

Look for crowded groups on young leaves and buds, white shed skins, and sticky honeydew. Sooty mold grows on that honeydew, and ants often tend the colony. Heavy feeding can curl and stunt new growth, and aphids can carry plant viruses.

What to do:

• Knock them off with a strong water spray, or squish or brush them off.
• Cover seedlings and transplants with row cover, and remove it once the plant flowers.
• Skip extra nitrogen, since lush growth attracts aphids.
• Let ladybugs, lacewings, and parasitic wasps do their work, and see which plants repel aphids.
• Save pesticides, including insecticidal soap, for last, and try the lowest-toxicity option first.

2. Slugs and snails: Trap and hand-pick at night

Slugs like cool, wet places and feed mostly at night or on heavily overcast days. UMD Extension says they leave silvery slime trails and chew ragged holes in leaf interiors, not along the edges.

They hit seedlings, leafy crops, and tomatoes. They hide under debris during the day.

What to do:

• Hand-pick at night, and drop slugs into soapy water.
• Set out moistened boards or shelters as traps, and check them each morning.
• Make borders of gravel or sand around plants.
• If you use bait, UMD says baits with iron phosphate or ferric sodium EDTA are allowed in home food gardens and are less toxic to pets.

3. Japanese beetles: Tap them into soapy water

The adult is a shiny metallic green beetle with coppery wing covers, up to 1/2 inch long. UMD’s Japanese beetle guide says adults appear from mid-June through August. They skeletonize leaves so they look like lace.

The grubs live in the soil and feed on roots, mostly in September and October. Grub damage is rarely serious except in lawns.

What to do:

• Hand-pick adults, or tap infested leaves over a container of soapy water.
• Skip baited traps. UMD says they attract extra beetles and increase damage.
• Use row cover on low crops.
• Watch summer lawn watering. UMD says irrigated lawns attract egg-laying adults.

4. Tomato hornworms: Hand-pick and check for wasps

Hornworms are big green caterpillars, 3 to 4 inches long, with a horn on the rear. UMD Extension’s hornworm page says feeding starts at the top of the plant. They eat whole leaves, and about 90 percent of the damage happens in the last growth stage.

Dark, pea-sized droppings on leaves or the ground are a clue. The caterpillars blend in well, so you often see the damage first.

What to do:

• Spray the plant with water. It agitates the caterpillars and makes them easier to spot.
• Pull them off by hand and drop them in soapy water. Their feet grip hard.
• Leave any hornworm with white cocoons that look like rice grains. UMD says they’re wasp cocoons, and that hornworm stops eating.
• Till the soil in spring or fall to expose pupae. UMD says hornworm damage rarely calls for an insecticide.

For more tomato help, see our guide to growing tomatoes.

5. Squash bugs: Crush the eggs

Adult squash bugs are flat, dark gray to brown insects about 5/8 inch long, with orange and brown stripes on the abdomen. UMN Extension says females lay clusters of about 20 eggs on leaf undersides, often in a V between veins. Seedlings and flowering plants are the most vulnerable.

Feeding causes yellow spots that turn brown, and severe feeding can wilt the plant.

What to do:

• Crush the eggs. UMN says they hatch in about 10 days.
• Drop nymphs and adults into soapy water if only a few plants are affected.
• Lay a board or newspaper on the soil at night. Collect the bugs under it in the morning.
• Clean up cucurbit debris in fall to remove hiding places. UMN says insecticides are normally not required in home gardens.

6. Cucumber beetles: Cover young plants

Striped cucumber beetles are yellow with three black stripes. Spotted ones are yellowish-green with 11 black spots. Clemson HGIC’s cucurbit pest guide says the beetles can kill young plants.

They also carry bacterial wilt of cucurbits, which overwinters in the beetle’s gut. The larvae tunnel into roots and stems.

What to do:

• Cover young plants with fabric row cover, and remove it when flowers open so bees can pollinate.
• Hand-pick the beetles.
• Pull weeds. Clemson lists weed removal as a control.
• Rely on natural enemies where you can.

7. Cabbage caterpillars: Use Bt on the young ones

Cool-season crops attract cabbage loopers, cross-striped cabbageworms, and diamondback moths. Clemson’s cool-season pest guide covers all three.

Look for ragged holes in leaves of broccoli, kale, and cabbage, and green caterpillars on the undersides.

What to do:

• Use Bt, a naturally occurring bacterium, on young caterpillars. Clemson says it controls young ones.
• Read the label, and apply as directed.
• Remove leftover plant debris at the end of the season.

8. Spider mites: Rinse, then use soap

Spider mites are almost too small to see. Clemson’s spider mite guide says the main sign is white stippling on leaves, and severe infestations make fine webbing. Twospotted spider mites are common in warm summer months.

Tap a leaf over white paper. Tiny dots that crawl are mites.

What to do:

• Water plants well in drought. Clemson says dry, stressed spots get mites first.
• Rinse leaves with water often enough that mites don’t climb back.
• Try insecticidal soap or horticultural oil next, and apply in the mid- to late evening.
• Skip oils and soaps in heat of 90°F or higher, or on drought-stressed plants, because they can burn leaves.

9. Cutworms: Protect seedlings with collars

Cutworms are moth caterpillars that cut seedlings off at the soil line. UMD Extension’s cutworm page says they feed at night, so you may find damaged plants and no caterpillar. They curl into a C when disturbed.

Damage is worst early in the season, on small, tender plants. UMN Extension lists seedlings as the most susceptible.

What to do:

• Push a 3-inch collar of cardboard, foil, or plastic into the soil around each stem.
• Scatter coarse crushed oyster shell, sand, or diatomaceous earth around stems.
• Hand-pick larvae and drop them in soapy water.
• Try floating row cover, and till in spring or fall. UMD also lists Bt for young larvae.

10. Harlequin bugs: Watch your cabbage family

Harlequin bugs are shield-shaped, up to 3/8 inch long, and black with yellow or red. UMD’s harlequin bug page says they mostly hit broccoli, cauliflower, collards, kale, and other cabbage-family crops. They suck sap and leave white stipples.

The eggs look like tiny white barrels with black bands, and they sit in rows of six under leaves.

What to do:

• Crush eggs, nymphs, and adults by hand.
• Cover crops with floating row cover.
• Spray nymphs with insecticidal soap, alone or with pyrethrum, or use neem oil, per UMD.
• Remove all crop debris at season’s end to remove overwintering sites.

What do gardeners get wrong about pests?

Most pest trouble gets worse for the same few reasons.

They spray first and look later. Many pests need a hand-pick, not a chemical. And a spray can kill the ladybugs and wasps that were already helping.

They skip the label. Clemson’s guidance is that the label is the law. It says what plants, areas, and rates are allowed.

They use traps that backfire. UMD says baited Japanese beetle traps attract extra beetles.

They leave debris. Squash bugs, harlequin bugs, and cutworms all use leftover plant matter to hide or overwinter.

We’d start with a magnifier and a bucket of soapy water. That handles more pests than most sprays. For more pest fixes, see our guide to controlling two common garden pests and our list of pest solutions for your garden.

Frequently asked questions

What is the worst garden pest?

It depends on your crops and region. Aphids show up almost everywhere, while squash bugs, hornworms, and Japanese beetles hit specific crops hard.

How do I get rid of garden pests naturally?

Use water sprays, hand-picking, traps, row cover, and natural enemies first. UMD says pesticides should be a last resort, and to try the lowest-toxicity option first.

Is hand-picking pests really enough?

For a home garden, often yes. UMD says hornworm damage rarely warrants an insecticide, and UMN says squash bugs normally don’t need one.

Are slug baits safe for pets?

UMD says baits with iron phosphate or ferric sodium EDTA are less toxic to pets. Always read and follow the label.

When should I check for pests?

Check often in spring and early summer, when young plants are most vulnerable. Also check at dusk or night for slugs, cutworms, and hornworms, which feed then.

Should I kill a hornworm with white cocoons?

No. UMD says the cocoons are from parasitic wasps. The caterpillar stops eating, and the wasps help control the next generation.