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Natural Chemical Found in Avocados Kills Fruit Flies

By Doris Stanley
April 2, 1997

A natural chemical already present in some types of avocados kills the Caribbean fruit fly. That’s the word from scientists with USDA’s Agricultural Research Service who were the first to discover that the chemical--called estragole--is toxic to the pests.

The ARS scientists found estragole in varying concentrations in the leaves of 14 varieties of Mexican avocados. But their tests turned up none of the chemical in seven Guatemalan and 13 West Indian types of avocados. Estragole is not harmful to humans.

The next step, the scientists say, is to find a way to manipulate the gene behind estragole to give plants such as fresh citrus natural resistance to the Caribbean fruit fly and possibly other insect pests.

Fresh citrus shipped to consumers in Japan, Thailand, California, Texas, Bermuda, and Hawaii must be certified free of the Caribbean fruit fly. The citrus industry relies heavily on pest-free certification for exporting.

Farmers have met these certification requirements by aerially spraying groves with malathion bait spray every 7 to 10 days during harvest. But environmental and health concerns have been raised about malathion, and the industry is looking for a replacement for the chemical.

Scientific contact: Michael Hennessey, USDA-ARS, Subtropical Research Laboratory, Miami, Fla., phone (305) 238-9321,