Posted by Nothing like coming up to the house to find large portions of your tomato plants stripped of their leaves.
The Tomato Hornworm is the caterpillar of the Five Spotted Hawk Moth, a relatively non-descript moth, but in its caterpillar stage wreaks havoc on tomatoes.
In the video I talk about the eggs of the parastic wasp, then I realized later the white protrusions from the caterpillar are the cocoons of the braconid wasp, not its eggs, which is even better, as soon they will hatch and parasitize more Hornworms. If you want the whole insect story, check out the Tomato Hornworm page at Wikipedia.
I have heard about cardboard collars one can put around a young tomato plant to prevent the Hornworms from crawling up the stem. Another way, according to Wikipedia, to reduce the resident population is to rototill the garden, as this will destroy hornworm pupae in the soil.
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On the premise that an ounce of prevention is worth a pound of cure, I did a bit of googling around. This one guy somewhat vaguely says on the Organic Gardening Forum at http://forums2.gardenweb.com/forums/load/organic/msg0210594620482.html that “I pinch the first or second leaf stem just hard enough to bruise it which causes the plant to produce an enzyme that is LETHAL to Hornworms. I have used this tech for 10 years and have not had one hornworm make it to adulthood.” PNAS (Proceedings of the National Academy of Sciences of the US) has an article at http://www.pnas.org/cgi/content/full/102/52/19237 that elaborates. Any mechanical damage or herbivory (chewing upon) induces tomatoes to produce “proteinase inhibitors (PIs), which are expressed rapidly and systemically in response to wounding.”
The short version is, in response to localized damage a whole tomato will plant will interfere with mr. hornworm’s metabolism and he’ll die. Yay!
If it doesn’t work, as a backup try delivering the chemical to the hornworm via a tea spray… of tomato plant tea. My mother says she recalls Crockett, the Victory Garden guy, saying that if you clip off hornworm-chewed stems and make a tea, and spray that on the tomatos, that it will kill off the worms.