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Managing around the weather

Most of Louisiana’s corn crop didn’t receive rainfall this year until it had reached the V6 growth stage, with much of the state’s acreage avoiding the continuous drenching that plagued fields a few miles north.

Growers, however, could be in for a wild ride for the remainder of the production year, because meteorologists are forecasting a high number of hurricanes for 2003. “A few of our folks are gun-shy because thousands of acres of Louisiana crops were not harvested in 2002 due to the hurricanes and tropical storms that hit the region last fall,” Lanclos says.

Regardless of the weather conditions, aflatoxin remains a threat to Louisiana’s corn crop, says Steve Moore, resident director of the Dean Lee Research Station in Alexandria, La. “Aflatoxin in corn is the No. 1 concern of most corn growers, although the last major year for the disease was 1998,” he says. The fungus can penetrate a corn plant in several different ways, but the primary culprit responsible for spreading the disease is insect pressure. Insect damage provides an easy entry for infection.”

Preventing drought stress in corn is critical to minimize risk of aflatoxin infection, Moore says. However, growers in 1998 reported high levels of aflatoxin in irrigated fields.

Louisiana corn yields have suffered in recent years due to relatively low rainfall and high temperatures, says Rick Mascagni, corn researcher at the AgCenter’s Macon Ridge Station near Winnsboro, La.

According to research studies, the stress that most affects corn yield is lack of soil moisture. What’s more, a lack of soil moisture and high temperatures also may predispose corn plants to aflatoxin, produced by the fungus, Aspergillus flavus.

“Much of the corn acreage in Louisiana is on soils that exhibit moisture stress at some time during the growing season,” Mascagni says. “Some soils are more drought-prone than others. For example, alluvial clay soils are subject to drought stress, due in large part to a relatively shallow rooting zone and physical characteristics that restrict plant-available soil moisture.”

Growers can take steps to minimize the risk of aflatoxin infection in their corn, says Moore. “There is no hybrid with advertised resistance, but good shuck cover helps.

Irrigating to avoid drought stress and fertilizing to avoid nutrient stress, particularly nitrogen, also will help to minimize the risk, as will adequate insect control.”

Moore also advises growers to harvest early and to use grain dryers. “Some growers have had success with harvesting at 25 to 26 percent moisture, and then using the air and heat in their bins to lower that moisture level,” he says.

To aid growers, Moore has helped classify corn hybrids according to aflatoxin content found in research studies. “We compared aflatoxin in each hybrid to the aflatoxin content of all hybrids at four locations, in both inoculated and non-inoculated ears. It is not known if hybrids will differ in their aflatoxin content in other years.”

Hybrids that have exhibited below average aflatoxin content across several different environments include: AgriPro/Garst 82511T; Asgrow RX828YG; Asgrow RX938; Croplan Genetics 762CL; Croplan Genetics 733BT; Croplan Genetics 827; Dekalb DK697; Dekalb DKC68-70; Garst 8288; Golden Acres 8112; N63-G7; Pioneer 31B13; Pioneer 3223; SS 670 BT; Terral TVX26R101YG; and Terral TV2130(MF).

Lanclos predicts corn will continue to gain acreage across Louisiana, as it appears to have done this year. Early estimates called for about 625,000 acres of corn this year in Louisiana, although 2003 acreage likely will fall closer to 425,000 acres, he says. A figure of 625,000 acres would get the state back to its pre-1998 status.

He sees a 10 to 15 percent reduction in the state’s dryland corn crop, but promising yields for irrigated corn acreage.

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