Just kidding. Though you could save on your food budget if you decided to incorporate this protein source into your diet.

Tomato hornworms only eat solanaceous plants, usually tomatoes and they will also feed on eggplant, potato, and pepper plants, as well as the solonaceous weeds horsenettle, nightshade, and jimsonweed. Typically there are two generations per year.

Biology and Life cycle

Have you seen these large beauties with impressive brown markings?

‘Tis a shame they will breed voracious, tomato-plant-eating monsters. The adult, also known as the “sphinx” or “hawk” moth, is a large, bulky moth with yellow abdominal spots and a 4 to 5 inch wing spread. The tiny front wings are not as noticeable as the hindwings with light and dark bands. The moths eat flower nectar.

The way its wings beat rapidly, while it hovers over a flower and extracts nectar, is the reason it is also known as the hummingbird moth.

The life cycle is short, only 30 to 50 days and is a wondrous example of complete metamorphosis. It begins with the eggs that hatch into larvae. The larvae become the hornworm pupae that finally mature into adult moths.

Hornworm eggs are oval and translucent green in color, measuring 0.10 centimeters across. The eggs are deposited singly on both the tops and bottoms of leaves in late springtime. Within 6 to 8 days after they have been laid, the hornworm eggs hatch into larvae.

Very similar to the tobacco hornworm caterpillars, the larvae are light green with black and white markings and are about 70 millimeters long. They feed on the foliage of the plant where the eggs were laid. Both the tomato and tobacco hornworm caterpillar go through 5 larval instars (developmental stages) that last about 20 days.

The first instar is solid white or pale yellow, and 7 white V-shaped stripes appear in later instars. The black abdominal “horn” give the caterpillar its “hornworm” name. The horn gets shorter as the caterpillar evolves through instars. The caterpillar is 3 1/2 to 4 inches in its final stage, when it seeks out a burrowing place or wanders so it can pupate.

The full-grown caterpillar burrows 10 to 15 centimeters into the ground and develops an oval, brown pupa with pointed ends. After 2 weeks moths come out of the pupae, mate, and lay eggs on tomato plants. In the fall, the pupae stay underground all winter and emerge as moths the following spring.

Cultural Control

Handpick the hornworms if you have a small garden. For effective control in a large garden, roto-tilling after harvest will kill about 90% of the pupae.

Biological Control

Tomato hornworms have many natural predators, including green lacewings and ladybugs.

Their most grotesque parasite is the small braconid wasp, Cotesia congregatus. The wasps lay eggs on the hornworm and the eggs devour the hornworm. You can see the egg cocoons as white bumps on the hornworm. A hornworm with white bumps should be left in the garden to support the beneficial wasps.

Dipel DF and Safer Garden Dust contain Bacillus thuringiensis (Bt), and and they effectively fight tomato hornworms. A naturally occurring bacterium, Bt is found in soil around the world. Non-toxic to humans and pets, there are several strains of Bt that kill only specific insects. It is not a broad spectrum insecticide, and does not kill beneficial insects such as honeybees, or predators and parasites of hornworms. The most common Bt strain, kurstaki, affects caterpillars that would turn into moths or butterflies; after the caterpillars consume the Bt they shrivel and die.

Other strains of Bt are used against mosquito larvae. Mosquito Bt Floating Donuts/Dunks contains Bacillus thuringiensis Berliner var. israelensis and controls mosquito larvae in small areas of still water for 30 days or more.

References:

http://www.vegedge.umn.edu/vegpest/hornworm.htm

http://www.buzzle.com/articles/tobacco-hornworm-facts.html

http://www.ext.colostate.edu/pubs/insect/05556.html

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