Control Hornworms With Natural Insecticides

Control Hornworms With Bt
In their caterpillar stage, tomato hornworms are vulnerable to insecticides only while they are still moving around and eating leaves and other plant parts. Treat the affected plant thoroughly with a product containing Bacillus thuringiensis (Bt) when the caterpillars are actively feeding. The hornworms eat the Bt, which is a bacteria that affects their digestion, as they feed. They stop eating and die within a few days. Using a duster, dust all parts of the leaves, especially the undersides, or apply Bt in liquid form with a hand pump sprayer.

All parts of the leaves, especially the undersides, should be thoroughly covered. Spraying the bottom half of leaves also keeps the viable Bt spores more active because they survive longer when not exposed to direct sunlight. Because Bt washes off with rain, reapply it in 10 to 14 days to be sure you control the problem. Read and follow label instructions for use, storage, and disposal of all insecticides.

Control With Pyrethrin/Pyrethrum Insecticide
The quickest tool for killing tomato hornworms is a pyrethrin/pyrethrum insecticide . This is a very safe product, but it will kill any insect it contacts, so use it only on the plant where the hornworms are a problem. You can further increase the effectiveness of this tool by mixing it with insecticidal soap. Mix about two thirds pyrethrin/ pyrethrum insecticide and one third insecticidal soap. This is particularly effective against serious hornworm attacks. As with any insecticide, always read and follow the instructions on the label for safe use, storage, and disposal.

Control Hornworms With Synthetic Insecticide

Virtually all the Synthetic Insecticides found in the garden center will effectively kill Tomato Hornworms. Like the natural pyrethrins, these pyrethroid products will kill any insect it touches, so use it carefully and in a very focused manner.