Hornworm Eats Tomato Fruit

Q: I am at my wits end with a pest eating my tomatoes. The past 2 days when I have gone out to pick the tomatoes that have just become ripe, I notice that they have these chunks taken out of them. The bite mark is fairly consistent, and I had one smaller tomato that had about half of it eaten away. Does this look familiar to you?

A: It is very familiar! You have a large hornworm that’s having supper every evening at your expense.

Hornworms have a voracious appetite. When they grow large, usually by July, one can devour a foot long tomato leaf in one day. Small ones are almost impossible to spot. Their green coloration is excellent camouflage against human and animal predators.

Though we refer to them as “tomato hornworm”, the most common hornworm on tomatoes is actually the tobacco hornworm.

You can try using a UV (blacklight) source to find them at night. They glow a ghostly green.

Fortunately, there are two insect enemies that have no problem finding tomato hornworms: both are wasps.

The tiny braconid wasp lays her eggs on an unlucky hornworm. The immature wasps consume the caterpillar from the inside and then make numerous white cocoons on the creature’s skin. Additionally, the common paper wasp loves to eat small hornworm caterpillars.

To avoid hurting your insect friends, spray or dust an organic garden insecticide containing Bacillus thuringiensis (B.t.) click for sources) on your plants in mid-May and every week thereafter.

The B.t. is harmless to humans, animals and insects but is fatal to caterpillars.

tobacco hornworm

tobacco hornworm eating tomato

tomato hornworm with braconid wasp cocoons

hornworm droppings

hornworm in UV light