Controlling insects that prey on rice crops was the focus of a recent LSU AgCenter workshop.
Agriculture consultants, farmers and LSU AgCenter faculty from across the Louisiana heard how to control the two main rice insects — the rice water weevil and the rice stink bug.
Mike Stout, LSU AgCenter entomologist, said seed treatment with Dermacor or Cruiser is a pro-active way to control weevils, but the decision to use those products has to be made prior to planting.
“I think the seed treatments are fairly compatible with integrated pest management,” Stout said.
The cost-to-benefit ratio has to be considered to justify the expense of a seed treatment, he said, pointing out that a yield loss of 0.5 percent to 1 percent can be attributed to each larva found on the roots of a rice plant. And water-seeded rice could attract weevils earlier in the season because the insects are attracted to water.
Cruiser, available commercially for the first time this year, has the added advantage of controlling the colaspis insect, he said, while Dermacor is less effective against that pest.
Stout said female weevils prefer young rice plants for laying eggs, so planting early could be the most important management practice growers could do to reduce a weevil problem. If a foliar insecticide application is required, the material works better on early-planted rice.
He said farmers also should consider staying away from low seeding rates in the range of 30 pounds per acre.
Delaying the flood until plants are at the mid-tillering stage also discourages weevils, he said.
A shallow flood at the depth of 2 inches is less attractive to weevils, Stout said, and high nitrogen fertilizer rates also should be avoided.
Natalie Hummel, LSU AgCenter entomologist, said the AgCenter will conduct a field study of weevil insecticides again this year to review the materials in farmers’ fields across the rice-growing area of the state.