"We know that when caterpillars chew on plants, eventually the plants produce chemicals attracting wasps that are the natural enemy of the caterpillar," says Dr. James H. Tumlinson, the Ralph O. Mumma endowed professor of entomology at Penn State. "Natural predators can be an effective method of biological control of pests in agriculture."
However, these predator attracting chemicals do not appear immediately. The first chemicals released are green leafy volatiles (GLV), the odor of new mown grass or crushed leaves. These are highly volatile and appear immediately so they are good candidates as signals to other plants.
To explore this, Tumlinson, working at the Center for Medical, Agricultural and Veterinary Entomology, Agricultural Research Service, U.S. Department of Agriculture, Gainesville, Fl., looked at how GLV influenced undamaged plants in the area by studying corn seedlings and beet army worm, a caterpillar that eats corn leaves as well as cotton, tobacco and other plants. The researchers exposed seedlings to GLV for an hour or overnight. They then tested the undamaged plants by either mechanically damaging them or mechanically damaging them and applying beet armyworm spit to the wounds.
"We discovered that . . . exposure to GLV primed corn plant defenses to respond more strongly against subsequent attack by herbivorous insects by increasing jasmonic acid biosynthesis and volatile organic compounds (VOC)," the researchers report in the current issue of the Proceedings of the National Academy of Science.
Jasmonic acid is a plant hormone that turns on plant defenses, including VOCs, which are the chemicals that attract the caterpillar's parasites and predators. They usually do not appear until hours after the init
Contact: A'ndrea Elyse Messer