Seen one of these tomato hornworms on your tomato plants? If so, you’ve got a problem. You have to get rid of it – them, actually, because there are surely more – and you have to do it quickly. These hornworms, actually the larval stage of the sphinx moth, before you even see them blending into the foliage, will eat whole leaves, small stems and parts of your green tomatoes. They don’t just eat tomatoes either, they enjoy peppers and eggplants as well as potatoes. Yes, when you see something is eating into your tomato leaves, start looking for these three to four inch hornworms!
The moth lays its eggs on the underside of the leaves, and it takes the little caterpillars about four weeks to mature so inspect the tomato plants early in the growth cycle to break the tomato hornworm’s destructive reign.
How to Stop the Tomato Hornworm
You have to get rid of them – so what are your options?
Pick off the Hornworms by Hand – These are huge pests so, despite the green coloration hiding them in plain sight, they should be fairly easy to visually spot once they get big enough, and you can pick them off with your hands. Once, you have ahold of it, you can either squash it under your feet (EW) or plunk it into a container of soapy water to drown it. Whatever, you do, don’t develop a compassion for the little buggers and throw them in your compost pile, as they’ll just crawl right back over and continue eating your vegetable garden.
Bacillus thuringiensis – BT is a soil-living bacterium from which a pesticide can be extracted. BT can be an effective pesticide when the hornworm larvae are small. To use BT against the hornworm just mix the BT with water and spray in all over the tomato plant, especially covering the tops and bottom of leaves (but don’t spray it until you get an excessive run-off). Use this weekly. Follow all the manufacturer’s instructions and precautions, of course, but BT appears to be safe for humans – more and more it is being incorporated into genetically modified plants so we’ll just have to see what the future implications for human ingestion of BT actually are.
Braconid wasp – This parasitic wasp will lay their eggs on the flesh of living hornworms so the developing wasp larvae will eat the hornworm alive as they develop. A starter colony of Braconid wasps can be purchased by mail order from garden or greenhouse supply houses. Oh, by the way, if you find a hornworm that is covered with little white egg sacs you probably already have a Braconid wasp colony nearby – lucky you! – and they are already attacking the hornworm. Leave ’em be and soon you’ll have lots of helpers in the hornworm war.
Good Gardening Practices Help Stop the Hornworm – Generally, good garden housekeeping practices like keeping garden debris piles away from the actual crops (pests can hide and breed there) is a good step toward holding bugs in check. Another thing you can do is to turn the soil over completely in the fall to help kill out the hornworm and other pests. And lastly, understanding the enemy pests life cycle can help defeat it (knowing what the eggs look like and where they attach, for example).
Don’t let the tomato hornworm’s appearance mean the end of your tomato plant’s production. There are ways to win over the pest that don’t include poisoning your garden and your family.
More Tomato Resources
- Companion Planting: What to Plant with Tomatoes
- How to Harvest Tomatoes
- Farmgirl’s Favorite Tomato Varieties