Traverse City Record-Eagle

Archive: Saturday

August 3, 2013

Ag Forum: Wild nightlife of garden pests

TRAVERSE CITY — Many northwest Michigan gardeners enjoy the annual challenge of growing their own tomatoes.

Anyone who has tried this has probably met face-to-face with one the biggest caterpillars of the garden - the tomato hornworms. There are two species in the Grand Traverse area, the true tomato hornworm (Manduca quinquemaculatus) and the tobacco hornworm (Manduca sexta); both will readily feed on almost any plant in the solanaceous family, which includes tomatoes, potatoes, eggplants and peppers.

Young caterpillars may already be munching in your gardens right now, but you may not be able to find them until they are much larger and have removed a lot of leaves and some of the tomatoes from your plants. They have remarkably effective cryptic colors and markings, allowing them to blend into the foliage and stems of their host plants. Most species have a distinct horn on their tail end, hence the term hornworm. They are members of the insect family Sphingidae, derived from the sphinx-like posture that many of the hornworm caterpillars assume when they feel threatened.

Although many people recognize the caterpillar stage, the adults, which are large moths, are not nearly as well known. The adults of most hornworm caterpillars are called hawk moths. There are over 120 species in this family known from the United States and Canada; the adults of the tomato hornworms are among the largest of the group. July and early August is a prime time to see the adults, if you know where and when to look.

The bodies of adult tomato and tobacco hornworms can reach two inches in length, and their wingspan may exceed four inches. The wings are delicately patterned in shades of black, gray, brown and white; their bodies are similar shades with bold yellow-orange spots down the sides of the abdomen. They are extremely strong fliers, able to travel many miles in an evening to find your garden and lay eggs on your plants.

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