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Dogwood, Hydrangea Chemicals Foil Key Crop Pest

Hydrangeas and dogwoods have more than beautiful flowers. The leaves from these plants contain chemicals that kill or stunt the growth of two key crop pests, U.S. Department of Agriculture scientists report.

Entomologists Billy R. Wiseman and James E. Carpenter of USDA's Agricultural Research Service in Tifton, Georgia, started on the research a few years ago as part of an ongoing effort to find and test natural products from plants that can be used as insecticides against the corn earworm and fall armyworm.

To find the plants, Wiseman didn't have to go far. He simply went into his backyard and picked leaves not only from his hydrangea bushes and dogwoods, but also from black cherry and Bradford pear trees.

At the agency's Insect Biology and Population Management Research Laboratory in Tifton, the researchers dried the leaves, ground them up, and added them to the pinto-bean-based lab diet they feed to their earworm and armyworm larvae.

"The hydrangea diet killed 100 percent of newly hatched larvae within 2 days," says Wiseman. "The dogwood, cherry, and pear leaf diets severely retarded the growth of the larvae. The larvae fed on them, but they couldn't digest them."

Earworm larvae cause an estimated 5- to 10-percent loss each year to corn, cotton, soybean, and other crops. Armyworm larvae damage about $30 to $40 million worth of corn, grasses, and other crops in the southeastern United States.

The scientists are looking for an outside cooperator to help identify the active insecticidal ingredients in the leaf chemicals and to develop spray or bait formulations for these natural pest controls. Once the active ingredients are identified, Carpenter says, it may be possible to genetically engineer the insecticidal compounds into crop plants. -- By Sean Adams, ARS.

James E. Carpenter is at the USDA-ARS Crop Protection and Management Research Unit, Tifton, GA 31793; phone (229) 387-2348.