Scientists to Caterpillar Pests: Chew on This

By Tara Weaver-Missick
December 13, 1999

Chemical cues in the spit of tobacco budworm and corn earworm caterpillars cause plants to send out defensive signals when the caterpillars chew on them, Agricultural Research Service scientists have discovered. Small wasps, natural enemies of the caterpillars, then follow the defensive signals to find and sting the caterpillars.

The larvae of these insect pests are a major problem in cotton crops, but also in corn, soybeans, sorghum, sunflowers, tobacco and peanuts.

In laboratory studies at the ARS Center for Medical, Agricultural and Veterinary Entomology’s Chemistry Research Unit in Gainesville, Fla., chemists James H. Tumlinson and Naoki Mori discovered the chemicals in the spit of the budworm (Heliothis virescens) and earworm (Heliocoverpa zea).

This research builds on previous findings that beet armyworm caterpillars elicit a chemical “S.O.S.” response in plants. Surprisingly, they found that budworms and earworms produce the same compounds that are present in the spit of beet armyworms.

Oddly, plants are able to distinguish which insect is nibbling on their leaves and give off the proper distress signal to attract that insect’s natural enemy.

The scientists hope that by studying plant-insect interactions, they can develop plant varieties with more powerful chemical defenses against insect pests.

Mori will present these findings at the Entomological Society of America’s Annual Meeting to be held this week, December 12-16, in Atlanta, Ga.

Scientific contacts: Naoki Mori or James H. Tumlinson, ARS Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Fla., phone (352) 374-5731, fax (352) 374-5781, jtumlinson@gainesville.usda.ufl.edu.