Giant, hungry caterpillars gnawing on Lowcountry foliage, fruit

This tomato hornworm has been parasitized by a broconid wasp, which has laid eggs in the caterpillar.

Kids grow so fast.

One day they’re in diapers and the next they’re getting speeding tickets. It might take 16 years for that to happen, but it goes by quickly.

For insects, growing up only takes one summer. You can find extra-large and extra-hungry teenage caterpillars this time of year. Instead of leaving empty milk jugs in the refrigerator, they’ll be devouring foliage and fruit.

The tomato hornworm is one of the largest caterpillars you’ll see in the Lowcountry. They can reach up to four inches in length. You would think a critter that size would be easy to spot, but they are the exact same color as tomato leaves. They also hang on the lower side of a stem and go completely still when anything comes near. You’re likely to spot them when all the tomato leaves disappear overnight. Large pellets of frass (excrement) decorate the ground as these eating machines leave barren stems in their wake.

They sport a red thorn on the end of their abdomen, a warning to any predator that might reach for them. The thorn, however, is a bluff and poses no threat to bare fingers. Picking them off one at a time might be gross but it’s harmless. Simply keeping an eye on your tomato plants to catch them early is key to control.

However, there is one instance where you may leave tomato hornworms on your tomato plant. If oblong eggs are attached to the body, then the caterpillar has been parasitized by the broconid wasp. These gnat-sized wasps have already laid eggs in the caterpillar and the offspring have fed on the insides. What look like eggs are actually parasitic wasp pupa waiting to hatch into adults that will seek out more tomato hornworms. Leaving this caterpillar alone will support beneficial insects.

Another hungry caterpillar that will soon be making an appearance is the azalea caterpillar. Like the tomato hornworm, azalea caterpillars feed on only one host. If you guessed azalea, then give yourself an A. Not only do they feed only on azaleas, but the offspring frequently come back to the same azalea each year.

The body is striped and the legs and head are red. They only get 2 inches long but they feed in packs, often mobbing a single branch. Once the foliage has been decimated, they’ll move on to the next branch. In severe infestations, several branches will be covered. From the front porch, the shrub might look like it’s moving.

They defend themselves with a threatening pose. Touch a branch and all at once the caterpillars will aggressively rear their head and abdomen with legs extended. If you’re squeamish about creepy-crawly things, it’ll give you second thoughts. But these things are as dangerous as a palmetto bug. But you’re probably not crazy about them, either.

Simply pruning the infested branch and disposing is the safest approach. There are many insecticides that will control them, but one of the safest is Bacillus thuringiensis, a bacteria commonly known as Bt. If left untreated, azalea caterpillars can completely defoliate a shrub. In most cases, the plant will survive but repeated attacks can weaken it.

There are caterpillars that do sting such as Io moth caterpillars and saddleback caterpillars. When in doubt, don’t touch an insect with your bare hand. It’s usually obvious which ones are a legitimate threat, but like the tomato hornworm and azalea caterpillar, more of them put on a good show. For instance, the gulf fritillary caterpillar is spiny and orange. You’ll likely find it on a passionflower vine, but this immature butterfly will cause minimal damage to the vine and is harmless to touch.

Another impressive imposter is the hickory horned caterpillar. This caterpillar is just short of a hot dog in length and girth with devilish horns on front and back. No predator would dare touch it, but it turns out this harmless insect is all bark and no bite.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, e-mail him at tony. bertauski@tridenttech.edu.