New pest for crop in Louisiana: European corn borer hits rice fields

Entomologists in Louisiana have found an infestation of European corn borers in a 200-acre field of Cocodrie rice in Morehouse Parish, according to Boris Castro, a rice entomologist with Louisiana State University in Baton Rouge.

“The European corn borer (ECB) is now added to our list of insect borers affecting rice in Louisiana, which previously included the rice stalk borer and the sugarcane borer. There are no previous reports on European corn borer in rice, and, therefore, this infestation is new not only for Louisiana rice but for other rice-producing areas in the United States,” Castro says. “At this time, the infestation seems to be localized in northern Louisiana.”

Identified by its reddish-to-black head capsule and flesh-colored body, the European corn borer also has two distinct light brown spots on the top of each abdominal segment and a distinctive dark band around its mid-section.

Detected Aug. 6, the European corn borer infestation near Bonita, La., averaged 75 percent of affected plants. Adult pests were first observed moving from maturing corn fields to the rice during the third week of July, and their identity of was confirmed Aug. 11 by the USDA-ARS corn borer lab in Ames, Iowa.

Castro says the “severe” infestation was detected in time to apply a pyrethroid insecticide to the affected rice crop. Although rice plants were at heading stage, most of the European corn borer larvae were still feeding on the leaf sheath and had not entered the stalks.

Larvae spend approximately one week feeding on the leaf sheath tissue before entering the stem, at which time they can no longer be reached by foliar insecticides.

Castro says the European corn borer can be managed in much the same way growers manage sugarcane borer infestations in rice. However, no threshold levels have been developed for borer species in rice in Louisiana, and none of the foliar insecticides recommended for rice in Louisiana have a label for borers.

On the upside, unlike the sugarcane borer — for which no pheromone traps are available — there is a pheromone for the European corn borer, which allows entomologists to better monitor the pest.

Castro says field demonstrations and experiments using Karate and Mustang Max at the highest labeled rates indicate the two foliar products may have a potential for borer larval control. “The success of the control program depends on the foliar insecticide being applied before the larva enters the stalk,” he says. Research conducted in Texas and Arkansas against borer species also indicates that Icon treatments in drill-seeded rice may offer some degree of protection against the pest.

Area-wide crop residue destruction is still the most effective tool for reducing borer complex infestations the following year, but its feasibility is reduced under increased production costs and reduced tillage systems, he says.

To limit exposure to possible corn borer infestations, Castro recommends early planting within the recommended planting dates to avoid increased populations of borers moving from maturing corn and sorghum fields in central and northern latitudes of the state.

According to Castro, the European corn borer was reported in Louisiana corn during early June 2003, marking the first confirmation in Louisiana in the past 41 years.

“In north Louisiana, corn is now being harvested and grain sorghum is reaching maturity. This results in lots of European corn borer adults moving from matured corn into available crops, such as rice,” he says.

“Rice is susceptible to stem borer damage from panicle initiation up to panicle emergence. This is important because some late-planted rice fields in central and north Louisiana are at heading stages. While corn and sorghum may sustain several borer insects and still produce an ear (corn) or a panicle (sorghum), in rice it only takes one borer larva to prevent panicle filling. Even in heading rice, the borer larva may chew on the narrow panicle neck during grain fill, resulting in empty panicles and direct yield losses.”

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