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Tobacco Hornworm


 

COMMON NAMES: Tomato Hornworm, Fivespotted Hawk Moth, Sphinx Moth

 

SCIENTIFIC NAME: Order Lepidoptera, family Sphingidae, Manduca quinquemaculata

 

SIZE: Adult—2 1/2", larva—3" to 4"

 


  Photos by Mike Mirabal

 

IDENTIFICATION: Adults are narrow-winged gray moths with rows of orange dots along furry abdomens. They drink nectar from flowers at dusk. Torpedo-shaped body. Larvae are green caterpillars with a black horn on the tail (tobacco hornworm has a red tail) and white diagonal marks on the side. Eggs are round and green.

 

BIOLOGY AND LIFECYCLE: Caterpillars are seen more often than the adult moths. They pupate in cells in the soil. Large brown pupae overwinter in soil and emerge in June and July. The pupa has a tongue case resembling a jug handle. Females lay eggs singly under leaves.

 

HABITAT: Tomatoes, potatoes, eggplant, green peppers, tobacco plants, and various weeds.

 

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  Photos by Sandi Holmes

 

FEEDING HABITS: Caterpillars feed mostly at night on foliage of nightshade plants like tobacco and tomato. Moths sip nectar from flowers.

 

ECONOMIC IMPORTANCE: Can defoliate plants overnight. The adult with its long proboscis is necessary to pollinate deep-throated flowers and night bloomers.

 

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Photo by Sandi Holmes

 

NATURAL CONTROL: Birds, parasitic wasps, and braconid wasps attack the worms. Trichogramma wasps attack the eggs. Skunks.

 

ORGANIC CONTROL: Hand-pick caterpillars. Spray Bacillus thuringiensis products as a last resort only. Release lady beetles and lacewings to attack eggs.

 

INSIGHT: There are some 100 species of this moth in this country. They include the tomato hornworm, tobacco hornworm, hawk moth, and hummingbird moth.

 

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Tobacco hornworm pupa photo by Truman Smith

 

A single worm can eat most of a tomato plant before pupating. Because of their large size and appetites, the adult females usually deposit only one egg per plant. The larvae of most species have a horn at the end of their body, which gives it some protection--at least from humans who are scared of being stung. However, the horn and the mouth of these caterpillars are harmless. In some species the developing moth's tongue or proboscis is so long that the pupa has a sheath curving out from the head and away from the body and then back, resembling a jug or pitcher handle.

 

They are easy to hand-pick but are often missed because they blend so well with the plant. Hungry skunks that nightly patrol fields love to eat tomato hornworm.

 

The adult moth could be considered beneficial. With that long proboscis, they are necessary pollinators, able to feed on the nectar of deep-throated flowers and—since they are active at night—of flowers that open only at night.

 


 

A Howard listener story:

"Several years ago I had a heavy infestation of tomato horn worms.  Their color so closely matched the foliage that I had great difficulty finding them in sunlight. Just on a hunch, I went into the garden at night when it was quite dark with an ultraviolet lights of the type used by mineral prospectors.  My hunch was correct, hornworms fluoresce brilliantly under ultraviolet light. It was then very easy to pick them off of the vines." How is that for scientific bug control?

 

For more information, visit the Utah State University Plant Health Extension site for a comparison of Tobacco Hornworm and the Tomato Hornworm.

 

 

 

 

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