Yes, you should remove tomato hornworm caterpillars from your plants in most cases. The one exception is when you spot white cocoons on the caterpillar's back. Those cocoons mean parasitic wasps are doing the job for you. Every other hornworm should come off your plants as soon as you find it.
When I first started gardening, I made a mistake I still regret. I found a hornworm with white bumps on its back and tossed it in my soapy water bucket. A friend told me later that I had just destroyed dozens of parasitic wasps that would have guarded my garden all season. I felt terrible about that. Now I check every single hornworm for cocoons before I pull it off.
Knowing when to remove hornworms starts with a quick look at the caterpillar. Check its back for small white cocoons that stand up like grains of rice. If you see them, leave parasitized hornworm alone and let nature do its work. The wasps inside those cocoons will come out within a week or two. They'll start hunting for more hornworms to parasitize right away in your garden.
For hornworms without cocoons, speed matters a lot. A single caterpillar in its final growth stage causes over 90% of the total foliage damage from its whole life as a larva. Those first few weeks as a tiny green caterpillar barely dent your plant. But once a hornworm reaches full size, it can strip a whole branch of your leaves in one night. Waiting just two or three days costs you a lot of foliage.
UC IPM gives you a clear framework for your decision. Their guidance says to treat hornworms only when they cause heavy foliage damage or when they start eating your fruit. A couple of small hornworms nibbling outer leaves on a healthy plant aren't worth your worry. But a large caterpillar chewing through main leaves or biting into your green tomatoes needs to come off right away.
The removal process is simple for you to do. Grab the hornworm near the middle and pull with steady, firm pressure. Its prolegs will hold on for a moment before letting go of the stem. Drop it into your bucket of water with a squirt of dish soap. Then check the rest of that plant and all your nearby tomato, pepper, and eggplant plants. Follow the trail of dark droppings on leaves and soil to find ones you missed on your first pass.
In my experience, making hornworm checks part of your evening routine is the best thing you can do. A quick five-minute walk at dusk catches new arrivals before they reach their big, destructive stage. This keeps your plants healthy and your harvest on track. Your tomatoes depend on you catching these pests early. Your beneficial wasp population depends on you knowing which ones to leave behind.
Read the full article: Tomato Hornworm Guide for Gardeners
