Mild Winter Might Affect Rice

Weeds prospered through the off-season, insects could follow - or not.

Published on: Mar 28, 2012

Bruce Shultz

LSU AgCenter  writer

LSU AgCenter experts say the mild winter may or may not cause increased pest problems for the 2012 rice crop.

Weeds are already showing signs they have prospered during the off-season, according to Eric Webster, LSU AgCenter weed scientist.

Because of high diesel costs, farmers aren't likely to release water after getting flooded by this spring's rain, Webster said, and that will allow alligator weed to flourish after the warm winter gave it a head start.

Mild Winter Might Affect Rice
Mild Winter Might Affect Rice

"I'm seeing bigger alligator weed problems than I've ever seen this early," Webster said.

Because of heavy rains that flooded fields, many farmers have been unable to kill weeds.

"We're going to have a big problem with people planting into already established weeds," he said.

Some farmers take the approach that they will wait until all weeds are up before they spray herbicides to clean a field all at once, Webster said, but they should try to keep a field as clean as possible for a month after a crop's emergence. "The biggest yield losses from weeds come in the first three to four weeks after emergence."

Webster said many farmers are now more likely to skip a preplant herbicide application and plant into the water instead of draining a field, killing weeds and then drill seeding.

"We're going to be fighting more and more of these early weed problems," he said.

Steve Linscombe, director of the LSU AgCenter Rice Research Station, said many farmers are opting to plant conventional rice varieties instead of Clearfield, which is a herbicide-resistant rice, because of the lower seed costs and the current lower market price for rice. This would prevent farmers from using herbicides to kill the weed red rice.

Don Groth, LSU AgCenter plant pathologist, said the warm winter increased the potential for more of a disease problem.

"A lot of things probably overwintered better than they would have," he said.

But he said seedling diseases that occur with cold weather during and after planting won't be as prevalent.

If the wet weather continues, sheath blight and blast will be more of a problem, he said.

Groth said the warm temperatures also favor Cercospora, but the susceptible varieties that suffered during the last major outbreak of this disease in 2006 are not as popular now.

Mike Stout, LSU AgCenter entomologist, said research isn't available to show increased insect populations following a mild winter. He said the winter of 2010-11 was colder than usual. "We had a pretty average rice water weevil population last year."

Stout said there is data to show that a mild winter precedes an earlier emergence of insects. If that holds true this year, he said, weevils will be feeding on rice plants earlier.

"In terms of stinkbugs, I have no idea," Stout said.

Johnny Saichuk, LSU AgCenter rice specialist, said it's too early to say if the past winter will worsen pest problems. "My experience is we don't know until it happens."

Saichuk said he worries more about the dilemma faced by rice farmers who are ready to drill seed their crop, but their fields are too wet. "We are warm enough to plant, and we can't plant."

He said farmers who expected to drill seed their crop bought seed rice, but with flooded fields from recent rains, they may be considering water seeding by airplane. The problem is the amount of seed used for water seeding is considerably more than what is used for drill seeding, and additional seed may not be available in some varieties, Saichuk said.

Some farmers who drill seed normally don't pull their levees until after they plant, but that will be more difficult if water seeding is done instead.

"It's not that easy to switch over," Saichuk said.

He said without further rain, areas with silt loam soil that were flooded will take a week to 10 days to be suitable for planting, but heavy clay soils will require two weeks.

He recalled that March 2011 was warm, followed by a cold April. He said long-range forecasts aren't calling for a repeat of that occurrence, but forecasts didn't predict a deluge that hit parts of south Louisiana.

The warm, wet weather also could affect soybeans, often used in rotation with rice.

Asian soybean rust was found last month in Iberia Parish in an area where it has been detected previously. Clayton Hollier, LSU AgCenter plant pathologist, said the disease has spread in kudzu. "The conditions are perfect for it to grow and to spread."

The harvest of another rice rotation crop, crawfish, has been improving, according to Ray McClain, LSU AgCenter crawfish researcher, but he wouldn't speculate if that is a reflection of higher-than-usual winter temperatures.

"The catch has definitely picked up," he said, adding the catch seemed to be off earlier in the season, which probably was related to the last year's drought."