South American weed hurts cattle industry

It sounds like the name of an exotic new drink, but tropical soda apple has been more aptly described as the "plant from hell," say University of Florida. Gainesville researchers who have developed a natural way to control the rapidly spreading weed. "The highly invasive plant, which forms a dense and thorny thicket that is impenetrable to animals and people, has been classified by the Federal government as one of the nation's most noxious weeds," points out Raghavan Charudattan, professor of plant pathology with the institute of Food and Agricultural Sciences. "In Florida and seven southeastern states, it's literally taking over, displacing native plant species in infested areas."

He indicates that the weed native to South America, a serious environmental threat to natural areas and has become a major problem for the beef and dairy cattle industries. Sharp teems make the plant's foliage unpalatable, but livestock, wild animals and birds that eat the fruit help spread the seeds. Mature plants can produce 50,000 seeds that germinate under a wide range of conditions. Seeds also can be spread by compost, sod, and moving water.

Another concern, according to Charudattan, is that the cattle snipped out of Florida may harbor plant seeds in their digestive tracts and spread the weed to neighboring states. To stop the spread of seeds, Georgia, South Carolina, and southeastern states may require Florida cattle to be held on weed-free Pastures for 10 days before being shipped. "Pastures infested with the weed have less area available for cattle grazing, which means the stocking rates--the number of animals per acre--must be reduced." Charudattan indicates.

Until now, the only way to control the weed was with repeated mowing and chemical herbicides. However, applying herbicides is a problem for the cattle industry because of possible chemical residues in milk and meat. Charudattan maintains that a common plant virus can be used to kilt tropical soda apple, and he is seeking commercial partners to produce and market the virus as a natural biocontrol and bioherbicide. The virus, which can be applied easily and inexpensively with a portable backpack sprayer, is effective against tropical soda apple under a wide range of temperatures and year-round growing conditions.

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