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Arkansas study: Shallower water reduces rice pestSTUTTGART, Ark. (AP)--Rice farmers who want to reduce their costs can try flooding their fields at shallower depths to protect against rice water weevils, according to research by the University of Arkansas System's Division of Agriculture. John Bernhardt, an entomologist at the division's Rice Research Center, said growers asked him if there was a way to use agricultural practices to combat the pest. "Most years, rice water weevils are our number three pest," Bernhardt said. "They're in every rice field in Arkansas and some farmers have a real problem with it." Bernhardt said rice water weevils are attracted to rice fields at the onset of flooding. Previous studies have shown that adult weevils lay eggs in plants of all ages, but the highest densities of larvae were found in areas with deep flood. He said farmers usually know which of their fields will have weevil problems, and they were looking for a way to control the pest without costly insecticide treatments. Two test plots were planted at the center and scientists monitored the natural infestation and the effect on crop yields. The plots had variable flood depths over different lengths of time. No insecticide was used. At three and four weeks, the plots were sampled for rice water weevil larvae. Bernhardt said the plots with a 4-inch flood had the highest density of rice water weevil larvae. Rice plots with a 2-inch permanent flood or a 2-inch flood for four weeks before being raised to 4 inches had significantly fewer larvae. All treatments yielded similar amounts of rough rice, he said. No blast disease--a concern for reduced flood levels--was noted in any of the plots. "Larvae populations in these fields were reduced about 30 percent in last year's tests and about 28 percent this year," Bernhardt said. "Reduced flood level is not a substitute for chemical control, but, for some people, it can reduce water use and maybe keep weevil populations below the threshold where they will need chemical insecticide." Bernhardt said he also has conducted tests in which flood was delayed, and this practice gave some control over rice water weevil populations. He said combining the two practices could help manage rice water weevils. 9/22/08 Date: 9/17/08 Advertisement
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