A combination of early planting date and insecticide application to control rice water weevil in conservation till rice pays off, said a Texas A&M University entomologist.
“Experience shows the earlier we plant the fewer problems we have with insects in general,” M.O. Way reported during the recent Conservation Tillage Cotton and Rice Conference in Houston, Texas.
“But that's not always the case,” he said. In fact, in a 2003 experiment on the Texas A&M Agricultural Experiment Station at Beaumont, Texas, best yields came from treated plots planted April 1. That date was better than the March 13 planting date, but the least productive date was the latest, May 16, Way said.
Keys to efficient pest management, he said, are “integrated control tactics and production practices that minimize pests and maximize control. Farmers should consider injury threshold levels and the cost of applications versus the amount of injury likely from an insect infestation.”
He also cautions rice farmers to be aware of the lag time between identification of a problem and treatment. “That's especially important for growers who depend on ground rigs to apply insecticides,” he said.
Way said an advantage with conservation tillage and a sound integrated pest management program is that farmers can plant early. “Early seeding usually means a better opportunity for a good ratoon crop, too,” he said. Controlling insect pests such as the rice water weevil and stem borers is also easier with earlier planting.
“Either very early or very late planting can avoid high levels of water weevils. But late planting dates may be associated with higher rice stinkbug and stem borer problems. Late planting may mean more rice whorl maggots as well.”
Way's tests indicate the latest planting date, even when treated, produced the lowest yields.
Early planting and water seeding “coincide with cooler water temperatures which are not as conducive to rice seed midge buildup,” Way said. “Cooler water also holds more oxygen, and that stimulates growth so the rice can outgrow insect damage.”
He said chinch bugs and fall armyworms are also associated with late planting dates. “With pests such as stem borers (rice stem borers or Mexican stem borers), if we see damage in the main crop we see more in the ratoon crop.”
In Way's test plots, he used Icon 6.2 FS, Karate, Mustang Max and Dimilin 2L.
“Untreated check yields showed significant yield reductions at all planting dates.
“We noted better than 800 pounds per acre advantage across all tests by treating with insecticides,” Way said. “The earliest planting dates — March 13, April 1, April 15 and April 30 — produced better yields than the May 16 seeding date. April 1 was the best.”
In 2004 tests, the advantage of treating for insect pests across all planting dates was $29.77 per acre.
Way also is looking at the performance of transgenic rice varieties with borers. Tests are promising.