|
back
| home
University
of Rhode Island GreenShare Factsheets
Tomato
Hornworm
Manduca quinquemaculata
Lepidoptera: Sphingidae
The tomato hornworm is a large
pale-green caterpillar with white and black markings. The
caterpillar can reach 9
to 10 cm (3 1/2 to 4 inches) when fully mature. A projection
or spike on one of the last abdominal segments gives the caterpillar
the name "hornworm." The adult moth, called a sphinx or hawk
moth, is a medium to large, heavy-bodied moth with narrow front
wings. The moth has a spindle-shaped body which tapers at both
ends and fairly thick antennae. The adult is a mottled gray-brown
color with yellow spots on the sides of the abdomen and a wing
spread of 10 to 13 cm (4 to 5 inches).
The hornworm feeds on the leaves and new stems of the
tomato plant, causing extensive damage. During July and August
they also occasionally feed on the fruit.
The adult moth lays eggs on the undersides of tomato leaves
in late spring. The eggs hatch in six to eight days and the
larvae pass through five or six stages, maturing fully in three
to four weeks. The fully grown larvae then burrow into the
soil to pupate. The pupa may remain in the soil all winter
and emerge as a moth the following spring, or, if the weather
conditions are suitable, the moth may emerge from the pupa
in two to four weeks. The moths emerge from the soil, mate,
and then begin to deposit the eggs of the next generation on
tomato plants.
There are a number of natural factors which help to control
tomato hornworm populations. One of the most common parasites
in home gardens is a small, parasitic braconid wasp. Many wasp
larvae feed inside the hornworm, eventually killing the caterpillar.
The cocoons containing pupae of these wasps are visible as
small white projections on the hornworm's body. Larvae with
cocoons sometimes move sluggishly, but seldom cause additional
feeding damage. They should be left on the plant so emerging
adult parasites can attack other hornworms.
Hand-picking the hornworms from infested plants in the
garden provides safe and effective control in small gardens.
It is often surprisingly difficult to find these large larvae
on the plants. Their large brown droppings are generally readily
apparent, however. Once you find one larva, others are much
more easily found.
Adapted from the Cornell
Cooperative Extension, 1999
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
|