Tomato Hornworm
How to Get Rid of the Tomato Hornworm
The tomato hornworm, Manducaquinquemaculata, is a pest that can do great damage to backyard gardens. They feed not only on tomatoes but also on potatoes, peppers and eggplant. They are seldom a problem on commercial farms. A close relative is the tobacco hornworm. With both of these hornworms it is the larvae or caterpillar which does the damage.
The caterpillars are very large, three to four inches in length. The tobacco hornworm is green with white stripes in a diagonal pattern and a red horn on the back end. The tomato hornworm is green with white stripes that are in more of a V or chevron pattern and its horn is black. If you look closely, the tobacco hornworm has six pair of yellowish-orange spots on its abdomen. Both kinds of hornworms can cause great damage and both turn into incredibly large moths, gray with five to six inch wingspans. These moths are known by several names, including sphinx, hummingbird, and hawkmoths.
Because of the large size of the tomato hornworm, they are easy to pick off plants. This should be the first method to try unless there is an incredibly serious infestation. After you have removed the tomato hornworm from the plant, you can kill it by dropping it into a bucket of water, squishing it, or cutting it up with shears. Be sure to till the soil in the fall to destroy any pupae that might be living there. For more serious infestations, a biological control is recommended--BT or Bacillus thuringiensis (Dipel, Thuricide).
After the hornworms have fed on the leaves, blossoms and fruit of the tomato plants for approximately one month, they burrow into the ground to pupate. There are two generations produced each year. They can severely damage the tomato plants unless there is an abundance of natural enemies or biological controls are used. The tomato hornworm seems to like warm inland locations and it is not much of a bother during cool temperatures.
The tomato hornworm has several natural enemies including the common wasp and the parasitic wasp, Cotesia congregates. The parasitic wasp lays its eggs on the hornworm and then feeds upon it. The wasp cocoons look like little pieces of fuzzy rice sitting on the body of the hornworm. If you should spot this condition, leave the worms alive so that they can hatch from the cocoons. Upon emerging, the wasps will kill the hornworms and then look for more hornworms to eat.
If you have had an infestation of the tomato hornworm, be sure to till in the fall as ninety percent of the larvae can be killed by this method. Also, do not plant tomatoes there in the following season but rotate your vegetables so that not only tomatoes but the other vegetables in the same family are not grown in the same space for at least three years. It is sometimes hard to spot the tomato hornworm because its green color blends in with the plant’s leaves, plus it starts by attacking the inner leaves of the tomato plant first.
If you want to have an abundance of tomatoes to eat and/or can in the fall, be on the lookout for the tomato hornworm and destroy it before too much damage can be done.