The braconid wasp is the most famous natural predator of tomato hornworms. This tiny parasitic insect kills caterpillars from the inside out. But it doesn't work alone. A whole team of predators attacks hornworms at every stage of life, from egg to full-grown caterpillar. You get free pest control that no spray can match.
When I first spotted a hornworm covered in small white cocoons, I almost brushed them off. I thought they were some kind of disease on the caterpillar. A quick search taught me those cocoons belonged to braconid wasps. I left that hornworm alone on my plant. Within a week, dozens of tiny wasps came out of those cocoons. That one caterpillar gave my garden a squad of defenders for the whole season.
The braconid wasp hornworm relationship works like this. A female Cotesia congregata wasp lands on your hornworm and lays her eggs through its skin. The wasp larvae hatch inside and feed on the caterpillar's body for about two weeks. They avoid vital organs at first to keep the host alive. When they're ready, they chew out through the skin and spin white cocoons on the caterpillar's back. Your hornworm stops eating and dies within days.
Egg Stage Predators
- Lady beetles: Adults and larvae eat your hornworm eggs right off the tomato leaves before they even get a chance to hatch.
- Green lacewings: Their larvae are aggressive hunters that consume hornworm eggs along with aphids and other small pests in your garden.
- Trichogramma wasps: These tiny wasps parasitize your hornworm eggs directly, killing the caterpillar inside before it ever emerges.
Caterpillar Stage Predators
- Paper wasps: These hunt small hornworm larvae on your plants and chew them up to feed their own young back at the nest.
- Braconid wasps: They parasitize larger caterpillars inside and produce dozens of new wasps from a single hornworm host for you.
- Ground beetles: Active at night, these predators catch hornworms that drop to your soil to pupate and eat them before burial.
Other Natural Enemies
- Garden birds: Mockingbirds, robins, and other birds in your yard hunt hornworms by sight and spot them despite their green color.
- Spiders: Large garden spiders catch young hornworms in their webs before the caterpillars grow too big for the silk to hold.
- Soldier bugs: Spined soldier bugs pierce hornworms with their beak and drain body fluids from small to medium caterpillars.
You can attract these predators to your garden with a few easy steps. Plant dill, fennel, yarrow, and sweet alyssum near your tomato beds. These flowers give adult wasps and predators the nectar and pollen they need to survive. A low dish of water with pebbles gives your beneficial insects a safe place to drink during hot weather. Building this kind of beneficial insects hornworm control system costs you nothing but a bit of planning.
The biggest thing you can do is stop using broad-spectrum pesticides on your vegetables. Products like carbaryl wipe out your beneficial insects along with the pests. Without these helpers, hornworm numbers bounce back harder than before. Let the wasps, beetles, and lacewings do their work for you. In my experience, nature handles your hornworm problem better than any spray bottle when you give it the chance to do so.
Read the full article: Tomato Hornworm Guide for Gardeners
