The hornworm:
It is a large worm and has a horn on the back. You can use an insecticide to kill the worm. For tomato Hornworms, if an average of one Hornworm per plant is determined on ten plants, treatment is warranted. Spot treatment is often effective, as this insect often is localized in a field. Hand-pick worms off plants and destroy. Handpicking is effective for small gardens. Bt (Bacillus thuringiensis) and other insecticides may also be used to control hornworms. Treat with a registered insecticide as labeled.

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