Hornworm
A green caterpillar as thick as your finger, up to four inches long, with a stiff horn on its tail end. It matches the leaf color so well that you usually find the bare stems and the droppings first.
Pest checklist
Four things to look for. If most of them match what you are holding, you are in the right place.
What gets rid of them
Gentlest option first. For most backyard cases the first one is enough, so try these in order and stop as soon as it works. If you do spray something, the product label tells you how — please read the notice further down.
1Pick them off
Go over the plants twice a week, follow the droppings up to the caterpillar, and drop it in soapy water. This alone usually handles a home garden.
Try this first2Leave the parasitized ones
If a hornworm is studded with small white capsules, leave it on the plant; it is already dying and it is producing more of the wasps that do the work.
3Spray Bt on small caterpillars
If they keep coming, treat with a Bt product, which only affects caterpillars and works best while they are still small.
bt thuringiensis caterpillar spray4Turn the soil in fall
Till or fork the bed after harvest to break up the brown pupae that overwinter a few inches down.
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Which plants get hornworm
Every plant we cover that gets hornworm, grouped by type — tap any one to open its page. A note beside a plant came from that plant’s own entry, because the same pest can be a minor nuisance on one plant and a serious problem on another. Plenty of plants we do not cover get it too.
Plant families hit hardest
Related plants often share the same problems, so if one plant in a family has it, check the others. The largest group here is Solanaceae, with 6 of the 6 affected plants.
- Solanaceae6 plants
When to treat
Check plants twice a week from midsummer on and pull them off by hand, but leave any hornworm covered in white rice-like cocoons where it is, because those are wasps that will hatch and kill more hornworms.
Timing only — the label is the law
This page tells you when to watch for hornworm and when treating is worth considering. It is not a recommendation to apply any particular product. Read and follow the product label before you spray — under federal law the label is the legal instruction, and using a pesticide against it is illegal.
- Check the pre-harvest interval. Every product that’s cleared for an edible crop sets a minimum number of days between spraying and picking. Find it on the label before you spray anything you intend to eat.
- Check the re-entry interval before you or anyone else works in the treated area again, and use the protective equipment the label names.
- Confirm the product is registered for your crop in your state. This page groups many different crops together, and a product legal on one of them is not legal on all of them — state registrations differ too. Your state pesticide agency or local extension office can confirm both.
- Rates and mixing instructions come from the label, never from us. We don’t publish them because they differ by product and formulation.
Other problems on the same plants
If a plant gets hornworm, these are the problems it most often gets as well, so they are worth checking for while you are out there. They tend to appear together; one does not cause another.