HORNWORMS ON TOMATO

a. Tomato hornworm moth (or adult) with wings spread; b, egg; c, larva, dark form; d, pupa (or resting stage); e, tobacco hornworm larva, light form. (a, about three-fourths natural size; b, about four times natural size; c, d, and e, about one-half natural size.)

HORNWORMS ON TOMATO

The moths of the hornworms that feed on tomato lay eggs on the under side of the leaves. The eggs hatch in 6 to 8 days or so.

The resulting larvae feed on the leaves and sometimes the fruits. The larva passes through five or six stages and reaches full growth in 3 or 4 weeks. The full-grown larva then burrows several inches into the ground and changes to a pupa. The pupa may remain in the soil all winter and transform to the moth stage in the spring, or, if weather conditions are suitable, the moth may emerge from the pupa after 2 to 4 weeks. In any event, the emerging moth makes its way to the soil surface and deposits eggs on tomato plants for the next brood of hornworms.

Control: Hand-pick the hornworms from infested plants in gardens. Dust field plantings with 10 percent TDE or with a mixture of equal parts of calcium arsenate and hydrated lime. The dusts should be applied directly to all parts of the plants at 30 pounds per acre. The treatments should begin early in the season and be repeated at weekly or 10-day intervals until the earliest formed fruits on the plants are about half-grown. TDE and calcium arsenate may leave a poisonous residue on the fruit; it should be removed by washing before the fruit is marketed or eaten.