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Building a better rice weevil trap

A rice water weevil trap developed by a University of Arkansas graduate student has proven an effective means of tracking this pest for rice management and research.

“This is a good example of a modest project, supported by the Arkansas Rice Research and Promotion Board, that has shown useful results,” said John Bernhardt, UA entomologist at the Rice Research and Extension Center near Stuttgart, Ark.

Raymond Hix, a Ph.D. student working with Bernhardt and UA entomologist Donn Johnson, developed the rice water weevil trap.

The trap gives researchers a new tool for assessing the effectiveness of resistant varieties and management practices, such as delaying flood, for controlling the rice water weevil. Producers have a more reliable means of scouting for the pests to determine if and when to apply pesticides.

“The old scouting method was based on counting leaf scars,” Bernhardt said. “Above a threshold of damage to the plants, you applied pesticide. But it was inconsistent and proved ineffective with the latest available pesticides.

“Once you place this trap in a flooded field, you'll know in three or four days if the rice water weevil population is increasing,” he said. “It gives you information early so you have more time to schedule an aerial pesticide application if you need it.”

The trap consists of a net barrier suspended between two floating traps. When a rice water weevil swims into the barrier, it turns left or right into one of the traps. Bernhardt said it's a passive trap that uses no bait or lure.

“It's important to check the traps every day once you set them,” he said. “Everything in the world swims into this thing. But it beats anything else we have for fast, reliable information.”

Bernhardt said he is still working to determine the best placement of the trap and how many are needed to give the most accurate picture of what rice water weevil populations are doing. “Environmental factors, like wind direction, have an impact on things like which direction the weevils are swimming,” he said.

“The next step is to find someone to manufacture it,” he said. “In the meantime, you just have to glue the parts together.”

Fred Miller is science editor for the Arkansas Agricultural Experiment Station. e-mail:

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