Corn earworm munches on corn kernels. Click the
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Corn Plants Alert Neighbors, Seek Help
Against Pests By Jim Core
Corn plants under attack from insect pests use chemical signals
not only to interact with beneficial insects, but also to stimulate early
defense responses in nearby plants, according to published findings from
Agricultural Research Service and
The results demonstrated the first proof of plant-to-plant
warning signals in corn plants.
The warning signals are chemical compounds called green leafy
volatiles (GLV). Shortly after coming under attack from pests, corn plants send
these volatiles into the air to draw support from the pest's natural enemies.
The volatiles, which smell like cut grass, attract caterpillar predators and
When the researchers exposed undamaged corn seedlings to GLV
from damaged plants, the seedlings' chemical defenses increased. But an even
stronger defensive reaction was triggered when seedlings were exposed to the
volatiles, purposely damaged and then treated with a beet armyworm caterpillar
substance to imitate insect attack.
Plants used as an experimental control were damaged, but never
exposed to GLV. They did not react as strongly, which suggests that the
volatile signals help prepare the plants' defensive reaction. Different,
night-time volatiles also stimulated a defensive reaction in neighboring
plants. Plants that were sensitized to GLV first and then damaged--but not
exposed to the caterpillar substance--did not react as strongly as they would
have if they had been exposed to the caterpillar substance.
Former ARS researcher James H. Tumlinson led the study before
retiring from the agency. He and his colleagues at ARS,
Pennsylvania State University and the
University of Florida reported their findings
in a recent issue of the Proceedings of the
National Academy of Sciences. Tumlinson, a chemist, is now a visiting
Penn State professor at the ARS Center for
Medical, Agricultural and Veterinary Entomology in Gainesville, Fla.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.