Scientists at the U. S. Agriculture Dept. are trying to help some key food crops that are being munched on mount a chemical defense against insects, much as the human immune system rouses itself to fight off microbes. Scientist Ann C. Smigocki of the Agricultural Research Service has built a gene out of two elements: DNA that acts as an on/off switch and a natural gene in plants that produces cytokinin, a chemical that caterpillars dislike.
When a hornworm caterpillar chomps down, the leaves' dying cells send out signaling chemicals that trip the switch triggering cytokinin production. Scientists previously tried to produce cytokinin continuously, but that slowed the plant's development. The cytokinin is only in the leaves and is not thought to be toxic to people. Trials on tomato plants will begin this summer, and Smigocki believes the technique could be adapted for pests that destroy soybeans and sugar beets.