Parades, Picnics, And Hornworms

Wherever you are, summer has its own rhythm. Wait for rain, go on a picnic, watch the parade, and look for hornworms. I never said all the rhythms were good. Hornworms are as much of our family traditions as playing summer baseball. I'll never forget the year we picked over 40 of them on just 14 plants in one day. I really don't like these critters. Maybe if I learned a little more about their lives I'd have a better appreciation for what I was squashing.

The first thing I learned is that what most of us call the Tomato Hornworm is actually the Tobacco Hornworm (Manduca sexta). The true Tomato Hornworm is more likely to be found east and north of here. The Latin name Manduca means glutton and the species sexta refers to the six spots on the abdomen of the moth that lays the eggs that become the Tobacco Hornworm. For some strange reason the common name of this moth is not the Six Spotted Glutton Moth but the Carolina Sphinx.

You may have already seen Carolina Sphinx Moths this year. They are easy to mistake for hummingbirds as they fly around looking for food. Sometimes they are called Hummingbird or Hawk Moths. At my house Four O'Clocks particularly attract them. The Carolina Sphinx lives as an adult for about a week then lays its eggs and dies.

The eggs are about 1mm in size and are a blue-green to yellow-green in color. If you see them on your plants pull them off and step on them. Eggs hatch in 1-3 days and the fun begins. It's hornworm time.

Hornworm caterpillars eat and eat. They are gluttons. Usually they are on our tomatoes but they will consume most any member of the Solanaceae family that includes peppers, potatoes, and eggplant. The typical hornworm is about 1”-3” long. It is tomato leaf green with a series of white stripes on its back. The most striking feature is a “horn”, which looks like a curved spine, at one end. This horn is harmless and is used to scare off predators. The end without the horn is the head and the horny end is its butt. (Please no jokes here because this is a family column.)

These caterpillars are pretty hard to spot. It is easier to see where the damage (missing leaves) is and then search that area. If you see stems with no leaves and little black spots (caterpillar poop) you have hornworm problems. Hornworms don't bite or sting so if you see one pull it off and step on it. They must taste pretty rank because chickens usually won't eat them. Other controls include parasitic wasps and Bt. Bt is a very safe “organic” spray that kills caterpillars and nothing else.

After gorging themselves on your favorite plants the teenage hornworm begins to wander and look for a place in the ground to bed down. While looking for a place to sleep the hornworm often pukes up some of its last meals. It reminds me of some of those college parties you hear about. The teenage hornworm is about to become a pupa.

The pupa, which live underground, looks like a brown cigar butt with a string loop at one end. That string becomes the tongue. If you find a pupa, it is probably tempting to cut off the string. That would be cruel. Just step on the pupae and get it over with. Often just tilling up the soil will expose the pupas and end their life cycles. This stage can last from 3 weeks to 6 months. Then the Carolina Sphinx emerges and we get to start the whole cycle over again.

Maybe I shouldn't mention this but this entire mess could have been avoided. It seems that the Tobacco Hornworm was introduced in a load of tobacco from Nicaragua in 1641. If they had only taken care of business back then. Now this insect is gaining popularity. Science teachers raise them to demonstrate the life cycles of moths. You can buy eggs for your own experiments. In 1996, Tobacco Hornworms were sent on the space shuttle as part of the payload. Your tax dollars at work. They probably wanted to see how hard they were to step on in zero gravity.