Tomato Hornworm, Manduca quinquemaculata. However, the tomato hornworm and tobacco hornworm Manduca sexta, are often confused with each other. They are very similar in appearance and both attack members of the Solanaceae family. The tomato hornworm is three to four inches long at full size (likely to be the biggest caterpillar we see in our gardens) and green in color with white v-shaped marks along its sides. A black “horn” projects from the rear of the caterpillar. Tobacco hornworms have diagonal white stripes and a red “horn.”
The tomato hornworm represents the larval stage of the hawk or sphinx moth, also known as hummingbird moths. The moths overwinter in the soil as dark brown pupae, then emerge and mate in late spring. They lay their eggs, which are round and greenish-white, on the undersides of leaves. The eggs hatch in four to five days, and the hornworm emerges. It spends the next four weeks growing to full size, after which it will make its way into the soil to pupate.
Signs of Tomato Hornworms:
Tomato hornworms are voracious, munching entire leaves, small stems, and even parts of immature fruit. While they are most commonly associated with tomatoes, hornworms are also common pests of eggplants, peppers, and potatoes. Most likely, you’ll notice the damage before you notice the hornworms, because their color helps them blend in so well with the plant foliage. You can also look for their black frass (droppings) on the foliage and around the base of the plant.
Effect on Garden Plants:
If it remains undetected for some time, it can deal some serious damage to the plant. They contain hearty appetites, which can make the plant die in few days. On the other hand, if they are detected at earlier stage, the plant will recover in a matter of days.
Organic Control for Tomato Hornworm:
Since the hornworm is quite large in size, the most effective and easiest way is to pick them with hands as soon you see one and throw out of the garden or maybe kill them. BT (Bacillus thuringiensis) is a good treatment for a bad infestation. If the larvae are small, then this is the most effective solution. If you are facing this problem every year, then you might need to rototill the soil in spring or in late fall before planting; it will destroy or bury them.
Sometimes the hornworms are covered with the white egg sacs. If you find some of them, let them stay in your garden because those are the eggs of a parasitic wasp known as the Braconid wasp. When the eggs hatch, you will get an army that is going to defend your garden from every kind of pest.
Read original article here: http://organicgardening.about.com/od/pestcontrol/p/tomatohornworm.htm