How to Get Rid of Green Horned Caterpillars

Get rid of green horned caterpillars without using chemicals.

The tomato hornworm, Manduca quinquemaculata, is a specialized feeder, which means that it only dines upon specific items. This large green caterpillar wields a scary-looking horn or spike on its tail and eats only plants in the nightshade family. That doesn't sound so bad, until you find that tomato, pepper, eggplant and potato plants are included on this picky eater's menu. Fortunately for the organic home gardener, these green horned caterpillars are manageable without the use of dangerous chemicals.

Things You'll Need

• Repurposed plastic shopping bags
• Soapy water
• Bucket
• Insecticidal soap
• Bacillus thuringiensis, such as Dipel or Thuricide (optional)

Instructions

1. Check your plants every day for the presence of green horned caterpillars. Though they are quite large, tomato hornworms are easy to overlook due to their color. It's easiest to eliminate them from your garden while they're still small and before they damage plants to the point of defoliation. The best time of day to do this is during the cooler hours just after dawn or before dusk when the hornworms are most active.

2. Look the caterpillar over. If you see any elongated white ellipses sticking to it, drop the hornworm on the ground and leave it alone. Those white things are the eggs of Cotesia congregatus, and the green horned caterpillar serves as their incubator. These small parasitic wasps will soon kill the caterpillar when they hatch. Then the wasp larvae will go looking for more of the tasty treats to infest, forming their own natural caterpillar control force in your garden.

3. Pick a tomato hornworm off of the plant. Don't worry, it won't bite or sting you and that evil-looking horn is quite harmless. Hand-picking is the single most effective means of control for this pest. Drop the caterpillar into a repurposed plastic shopping bag and step on it. Drop the hornworm in a bucket of soapy water to drown it if you would rather not squish it.

4. Treat your plants with insecticidal soap very early in the morning before the sun gets hot. Use this product only when temperatures don't exceed 90 degrees Fahrenheit. Follow the packaging instructions carefully.

5. Apply Bacillus thuringiensis, such as Dipel or Thuricide, if you don't want to use insecticidal soap. It will kill this highly effective organism, just as it kills pests. Follow the packaging instructions carefully.

Tips & Warnings

• There are many solanaceous weeds that green horned caterpillars will eat, including nightshade, horsenettle and jimsonweed.

References

• University of Minnesota Extension; Tomato Hornworms in Home Gardens; Suzanne Word-Burkness and Jeff Hahn; 2007
• University of Minnesota VegEdge; Tomato Hornworm; S.J. Wold-Burkness and W.D. Hutchison; Last Modified May 17, 2011
• Colorado State University Extension; Hornworms and "Hummingbird" Moths; W.S. Crankshaw; February 2007
• University if Florida IFAS Extension; Clean Up Pests With Soap; Daniel F. Culbert, County Extension Agent; February 25, 2001