How to Get Rid of Inchworms in the Garden

Give inchworms four or five weeks and they will totally destroy any coniferous or deciduous tree in your garden or landscape. These leaf-eating worms dine day and night when they hatch from eggs in the spring or fall and leave gaping holes in the leaves, preventing photosynthesis.

These tiny buggers aren’t actually worms, but caterpillars born of the ‌Geometridae‌ family of moths. Known as inchworms due to their unique way of moving forward with few legs, they have legs in the front and the rear, with nothing in the middle. It’s a matter of push and pull as the central portion loops, forcing it forward and enabling it to devour more of your plant’s leaves.

Newly hatched spring and fall inchworms emerge in late April to early May, and this is the time to thoroughly examine your garden plants for any infestation of the tiny inchworms, when they are young and vulnerable and before they eat their way into adulthood. They reach maturity within four weeks, so your window to eradicate them as youngsters is short.

What Do Inchworms Eat?

‌Inchworms eat leaves of elm, apple, hackberry, basswood, oak, boxelder, maple and ash trees.‌ They also eat the leaves of shrubs growing beneath heavily infested trees.

A three-year-long scourge of inchworm infestation may kill a tree; therefore, eradicating them when they first emerge prevents the destruction of your garden or orchard.

Chemical Treatment of Inchworms

Inchworms must ingest any chemical used to eradicate them and Bt (Bacillus thuringiensis) and its subspecies Btk (‌Bacillus thuringiensis‌ subsp. ‌kurstaki‌) are considered the best chemical treatments to do the job. First discovered in Japan for the treatment of silkworm infestation, Bt works from the inside out, destroying the gut and causing paralysis, resulting in the inchworm’s inability to eat.

Bt is not harmful to beneficial insects or humans, and its subspecies Btk has been found to be most effective against the larvae of butterflies and moths. Spray it on the leaves, top and bottom, so that the chemical is ingested. Repeat every 3 to 14 days while the inchworms are feeding.

Organic Treatment for Inchworms

Bt products are authorized for use in organic gardens, orchards and woods. Bt, when applied when the caterpillars are infants, stops the cycle of moth-caterpillar-moth.

If you're not interested in using chemicals though, here are some alternative methods of inchworm control:

• ‌Natural Predators:‌ Ladybugs eat caterpillar eggs, and birds are attracted to the inchworms. Hedgehogs and green lacewing insects also favor inchworms in their diet.
• ‌Manual Removal:‌ You can also manually remove the inchworms, as they don’t bite. Wear thin gloves and place the harvested inchworms in a covered container. Or just shake the branch where the worm is found and let it drop into a container.
• ‌Inchworm Traps:‌ Create inchworm traps by wrapping the trunks of trees with sticky wrap which prevents the moths from climbing into the leafy canopy. A rag or log soaked in water and laid on the ground is attractive to the inchworms where they'll gather during the heat of the day. Inspect, collect and destroy.

Harvest them in early evening or dusk, or early morning. It’s best to burn them after they’ve been collected. Drowning also works.