Study: Plants can smell disease and react A skier rides a gondola past pine beetle infested pine trees in Winter Park, Colorado on April 7, 2009. UPI Photo/Gary C. Caskey IRAPUATO, Mexico, March 5 (UPI) -- Plants can smell infected or infested neighboring plants and then react to increase their resistance to pests or disease, a Mexican researcher says. Patricia Sarai Giron-Calva and her colleagues at CINVESTAV-Irapuato said while this so-called "talking trees" phenomenon was identified more than 20 years ago, the mechanism by which plants smell and process odors remained unclear. While insects or mammals smell odors within a second of exposure, plants require much longer exposure times to respond, they said. To determine how long it took plants to react to odors, the researchers exposed lima bean plants to an odor compound known to enhance resistance to bacterial disease in the bean plants. The scientists found lima bean plants mounted a high level of resistance to bacterial infection after exposure to the compound -- methyl salicylate -- for an entire day, but not after short exposure of 6 hours. "In contrast to insect or mammals, which can respond to odors within a second of exposure, the 'nose' of plants works in a fundamentally different way to perceive odors," they said. Plant-to-plant signaling in this instance is likely to involve the accumulation of odors in the receiving plant over a long period of time. The findings were published in the Journal of Chemical Ecology