From time to time in early summer, a very large brown and grey moth can be seen in the garden, visiting flowers, particularly large, white, fragrant ones. This conspicuous insect is variously known as the hawk-moth or sphinx moth. Its large size and rapid wing beat can be mistaken for a hummingbird. The Five-Spotted Hawk-Moth (Manduca quinquemaculata) feeds on nectar, but its larva (caterpillar) feeds on plants in the Solanum family: Tomatoes, peppers, eggplants, potatoes, and tobacco. Its close cousin M. sexta is known as Tobacco Hornworm and causes similar damage to the same group of crops.
The caterpillar is also a giant of the garden, growing up to 12cm (5") long, and is known as the tomato hornworm due to a growth that extends from its hind end. The adult moth emerges from a cocoon in early summer and seeks out tomatoes and their ilk upon which to lay eggs. The emerging caterpillars then feed ravenously on tomato foliage for four to six weeks before spinning their own cocoons and overwintering in the soil.
This insect is uncommon in British Columbia, but can be a serious pest in southern Ontario and Quebec, quickly destroying foliage, and causing dramatic damage to crops. While Tomato Hornworms can be hand-picked and removed from crops, the best organic defence may be companion planting with umbellifers. May umbelliferous plants attract wasps that will parasitize the caterpillars, and other insects such as ladybird beetles, which will prey on the eggs. Dill and other umbellifers can be grown alongside Solanum crops where this insect is a pest. Because the moth goes through its pupal stage in the soil, tilling at the beginning and end of the growing season is another way to disrupt its life cycle.