July 26, 2010

Frangipani Hornworm

7/26/10 |
Andy Wilson, Extension Specialist, Pinellas County Extension

Frangipani (Plumeria spp.)is a popular plant in the Tampa Bay area and much of the southern half of Florida. It produces clusters of showy flowers that are often fragrant. Visitors to Hawaii may recognize the flowers as one of those used in leis. Sometimes a colorful caterpillar, the frangipani hornworm, is also found on frangipani.

The frangipani caterpillar, also known as the tetrio sphinx or giant gray sphinx is found from Florida and some other parts of the southeastern and southwestern US though the West Indies, Mexico, Central America and South America to Brazil. In Florida, it has been found in most south Florida counties. It is also found here in Pinellas County.

The caterpillar is strikingly marked with black and yellow rings and a reddish-orange head. There is a black, one inch long, horn-like projection at the rear of the body. They can grow to a rather large size for a caterpillar, up to 6 inches long. Some entomologists have theorized that the coloration, which resembles that of the coral snake, may help protect the caterpillar from potential predators.

The frangipani caterpillar feeds on frangipani and some other members of the Dogbane Family including allamanda. On frangipani, each caterpillar can consume 3 leaves per day so that an entire plant can be striped of its leaves in as little as a few days. Once the leaves are gone the caterpillars will sometimes also feed on the plant’s branches.

At the end of the larval stage the caterpillar forms a pupal case in leaf litter or in the ground. Initially the pupa is yellow but after fully hardening it becomes a dark reddish-brown color. It is about 2 inches long.

The adult moths have brown, gray and white markings on their wings. Wingspan is about 5 to 5 ½ inches. The adult moths feed on nectar from flowers including periwinkle or vinca, Catharanthus roseus. After mating the female moths lay clusters of pale green eggs on the leaves of the host plant.

If there are only a few of the caterpillars on a plant they can often be adequately controlled by hand picking. Where there are too many caterpillars to make this practical, sprays containing Bacillus thuringiensis (Bt), such as Thuricide, can be applied. Unless complete defoliation occurs repeatedly, the caterpillars usually do not threaten the plant’s survival.

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