Researchers seek to thwart Mexican insect pest

Published 12:00 am Monday, July 8, 2002

A destructive insect pest from Mexico is munching its way across Texas and approaching Louisiana – threatening the rice and sugarcane industries in both states.

Researchers and extension educators in Louisiana and Texas, along with representatives of both states’ departments of agriculture, are cooperating in a project to find ways to stop or at least manage the spread of the Mexican rice borer – the potentially serious threat to rice and sugarcane in Louisiana and Texas, according to Gene Reagan of the LSU AgCenter’s Department of Entomology.

Reagan and M.O. Way of the Texas A&M University Agricultural Research and Extension Center in Beaumont, Texas, received a grant from the U.S. Department of Agriculture to try to stem the movement of the insect that has found its way from Mexico to southeastern Texas and now threatens south Louisiana as well.

A moth native to Mexico, the Mexican rice borer is about the size of a horsefly. The larva bores into a rice stalk where it’s protected from chemical controls and predators and feeds unimpeded on the plant.

The borer first came to Texas’ lower Rio Grande Valley in 1980 and became a serious pest of sugarcane. It was first detected in the Texas rice belt in Jackson and Victoria counties in 1987 and currently infests about 75 percent of the main Texas rice-growing area, according to Reagan.

Farmers began planting sugarcane in southeast Texas in 1998 at the northern edge of that state’s rice-producing area, and the borers have been moving in that direction.

“The numbers are building up in rice areas of Texas and threaten sugarcane,” Reagan said.

Although the insects are a problem in rice, Mexican rice borers are a greater problem in sugarcane, where they can virtually wipe out a crop.

“The prospect is a devastating insect pest,” Reagan said. “It’s potentially worse on sugarcane than on rice.”

Reagan said the spread of the insect is particularly worrisome because the Mexican rice borer has never been found in Louisiana, and the state’s farmers do not have the best tools to manage the pests. The insect’s presence in Texas sugarcane is important to Louisiana because with no sugar mills in that part of Texas, the cane is shipped to Louisiana for milling.

If the borer shows up in southeastern Texas sugarcane, “there would probably be a quarantine,” Reagan said. “We just don’t have adequate control tactics in sugarcane.”

Reagan explained that rice seems to be more tolerant than sugarcane of the Mexican rice borer. With the help from both states’ departments of agriculture, county extension agents and farmers, the research team has been trapping insects and tracking their movements.

“We are carefully monitoring their movement with pheromone traps,” Reagan said.

In the past two years, traps have captured borers in seven additional counties in southeast Texas within 60 miles of sugarcane in Texas and 120 miles of sugarcane in Louisiana.

“Every crop has an economic injury level, but the economic severity of borers in rice seems to be not as much as in sugarcane,” Reagan said, adding, however, high Mexican rice borer populations can severely damage rice yields.

Some sugarcane fields, on the other hand, face a complete crop loss under certain stress conditions – primarily weather related.

“One of my bigger concerns in Louisiana is sugarcane growers don’t have the ability to irrigate as they do in the Rio Grande Valley in Texas,” he added, explaining irrigation reduces stress from dry weather and helps the plants withstand insect infestations.

“Without major controls, the Mexican rice borer is on the verge of becoming a major problem to these multi-state agricultural systems,” Reagan said, adding that the current program includes monitoring the insects’ spread and developing plans to counteract their destructiveness.

The team is exploring integrated pest management programs using resistant varieties, environmentally friendly insecticides and various cultural practices, as well as considering the possibility of regulatory actions when needed.

Currently there are no resistant sugarcane varieties in Louisiana.

The three-year, $200,000 federal grant Reagan and Way are working with provides for monitoring the spread and intensity of Mexican rice borer in southeastern Texas and southwestern Louisiana and monitoring for borers around Louisiana sugar mills. The researchers also have received funds from the American Sugarcane League and the Texas Rice Producers Board to help finance their efforts and support a graduate student working on the project.

In addition, the researchers will be developing management practices and identifying reduced-risk pesticides for rice and sugarcane producers, as well as developing procedures for getting the information to growers.