Hornworms are the camouflaged green caterpillars that like to munch on the leaves, stems, and the immature fruits of tomatoes, eggplants, peppers, and potatoes. Tomatoes especially seem to be their prey of choice. That's why most gardeners call them Tomato Hornworms.
In early summer, they hatch from moth eggs on the underside of the leaves and grow to 4 inches in 4 weeks. They typically have a black or red horn on their body, but they do not sting. During its growth spurts, the unnoticed hornworm can literally destroy your plants in a matter of days. You usually will spot their handiwork first, usually in the absence or bareness of leaves, and the sign of black droppings on the plant.
This ugly duckling, which eventually turns into the hawk or sphinx moth – also known as the hummingbird moth – is a rather stubborn intruder. The easiest and most effective way to protect your plants is to hand-pick the worms off whenever you spot them and either step on them or toss them in a bucket of soapy water.
Diatomaceous Earth and Neem Oil will also help de-populate the hornworm camp, but it may take a couple days to take full effect. Go ahead and pull off any hornworms that you see before any further damage can be done.
If the problem is reoccurring every year, till the dirt over in the fall and spring to destroy any overwintering larvae in the soil. For helpful companion plants, grow dill and marigolds near your tomatoes. Wasps will also serve as a natural predator against these pests, so if you spot their white eggs on a hornworm, let them be. The wasps will finish the job.
If you're growing tomatoes, hornworms are most likely to show up uninvited. Make them know they're not welcome. Never let them win!
What pest seems to be your nemesis in the garden? What have you found that works to fight the Hornworm?