How to Prevent Hornworms
- 1). Clean up the garden in fall. Remove old plants and debris, leaving the soil completely bare.
- 2). Cultivate the soil to a depth of 6 to 8 inches in fall. After two to three weeks, cultivate again to a depth of 2 inches. Cover the soil with a 4- to 6-inch layer of mulch.
- 3). Cultivate the soil in spring about 2 weeks before planting and again just before planting.
- 4). Spray susceptible crops with B. thuringiensis, commonly known as Bt, every two weeks until blossoms form. Bt is fatal to hornworms and other caterpillars but harmless to humans, pets and other wildlife. Use this intensive spray program only if you have a history of hornworm problems.
- 5). Encourage braconid and trichogramma wasps, which form parasites on hornworms. Plant flowers and herbs that attract these predators, such as dill, black-eyed Susan, evening primrose, wild buckwheat, candytuft, bishops flower, angelica, strawflowers, nasturtiums and yarrow.