Garden detective: Tomato hornworm can be scary critter

11/16/2013 12:00 AM

11/15/2013 11:09 AM

I found this creature in my tomato bed, and apparently he was the only one that came to dinner. Any help that you could give me as to what this is would certainly be helpful.

Leonard Ming, Rancho Cordova

You’re not the only one who found one of these mystery critters – especially in the vicinity of tomatoes.

Retired state entomologist Baldo Villegas recognized it immediately, thanks to the photos you supplied.

“The pictures were very diagnostic, and this made the identification a breeze,” Villegas said.

“The critter in question is a ‘tomato sphinx moth’ or ‘tomato hornworm’ pupa,” he said. “Most likely, Leonard had an infestation of tomato hornworms on his tomatoes that he didn’t know existed. The hornworms developed to maturity and then crawled down into the base of the tomatoes and turned into the overwintering pupal stage of this tomato pest.

“The pupae of tomato hornworms are very diagnostic in that they are big, being usually about 2 inches long and brown in color,” Villegas explained. “The mouth parts of the caterpillars take the shape of a long tube, which is called a proboscis. And in the case of tomato hornworm pupae, they look like the handle of a pitcher.

“The pupae that were created in the fall will remain in the soil during the fall and winter months and will produce the spring generation next year,” he added. “There are usually two generations of the tomato sphinx moths (per year).”

Knowing what the critter is answers one question. But what to do about it?

Destroy the pupae or more tomato hornworms will appear next spring.

According to University of California’s integrated pest management program, hornworms – which often grow up to 4 inches long – look scary but are easy to contain. The worms can be hand-picked off plants and discarded.

Natural enemies normally keep populations under control, note master gardeners. Hornworm eggs are attacked by Trichogramma parasites. There are also several predators such as green lacewings and damsel bugs that will keep these populations low. After harvesting tomatoes, rototilling destroys pupae in the soil and prevents adults from developing.

Whatever method, don’t let the pupae mature.

“Whenever I find them in my tomatoes, I usually squish them as I only find a few of them in my entire tomato planting,” Villegas said. “I would not recommend any other control technique.”

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