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New Mexico State University

New Mexico State University

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Boll Weevils Being Beaten; Eradication Plan Takes Hold

ARTESIA, N.M. -- New Mexico is declaring victory against the boll weevil. Farmers, federal and state agricultural agencies and New Mexico State University scientists say that we are at the tail end of a 10-year scientific effort to eradicate this notorious cotton pest.

NMSU entomologist Jane Pierce checks a boll weevil monitoring trap near Carlsbad. Farmer-run eradication programs are now in place throughout New Mexico. (11/30/2001) (NMSU Agricultural Communications Photo by Norman Martin)

A program that evolved from simple monitoring to all-out eradication is pushing the pest onto agriculture's back burner, according to entomologists with NMSU and the New Mexico Department of Agriculture (NMDA).

"Farmer-run eradication programs are now in place throughout New Mexico," said Jane Pierce, an entomologist with NMSU's Agricultural Science Center at Artesia. Eradication programs are currently being supported by NMDA and the U.S. Department of Agriculture's Animal and Plant Health Inspection Service. NMSU researchers have been developing pest management programs to suppress boll weevil populations and lower eradication program costs.

NMSU researchers found that slight changes in timing of planting, coupled with clearing nearby fencerows of weeds had a powerful, lethal effect on the flying beetles' ability to grab a foothold. Where boll weevils did get established, these management techniques reduced yield losses and kept insect populations low. "Anything that can be done to reduce boll weevil populations will lower eradication program costs," said entomologist Carol Sutherland with NMSU's Cooperative Extension Service.

Last century, boll weevils virtually wiped out the cotton industry in many southern states. After entering the U.S. in 1894, they infested more than 85 percent of the Cotton Belt from central Texas to the Atlantic Coast in less than 30 years, causing millions of dollars in losses. Fifteen years ago, boll weevils crossed onto the rugged Texas High Plains and shortly thereafter began an assault on New Mexico farms.

"The threat was real and it was serious," said Pierce, who early on championed the state's suppression efforts and authored a series of guides on boll weevil control. "The cotton industry in much of New Mexico would have gone out of business." According to the U.S. Department of Agriculture's Agricultural Statistics Service, the state's producers harvested 67,000 acres of cotton last year worth an estimated $26 million.

NMSU scientists found the best time to attack the weevil was when it was at its weakest, just as the bug came out of winter hibernation. As the pests emerge from weedy or urban areas during May and June, they hone in on cotton fields close to their overwintering sites, generally not flying more than two miles. NMSU researchers discovered that the longer they could deprive weevils of food in this overwintering cycle, the less trouble they had.

Basically it's a matter of numbers. "Boll weevil has a tremendous reproductive rate producing a generation every 16 days," Pierce said. "Many other insects take about 30 days."

Over the course of a season that means twice as many generations and a tremendous difference in numbers. "One breeding pair of weevils in the spring could result in over a trillion by the end of the season," she said.

The first boll weevil was trapped in 1991 in eastern New Mexico's Lea County. In the following years populations surged, causing severe economic damage and threatening viability of cotton production in the entire state.

In response, NMSU researchers launched a multifaceted assault, urging farmers to control weeds, delay planting, orient rows east to west to take advantage of direct sun and delay planting fields near good overwintering habitat until last. Other techniques included using seeding rates to produce between three to four plants a foot, and applying insecticide when squares, the cotton flower bud, reached the size of a match head.

Historically, more than a dozen predators are known to attack boll weevils, but few have had much impact. Boll weevil eggs, larvae, and pupae are well protected from most natural enemies by host plant tissues.

As adults, they're even tougher. In the fall these flying, fattened beetles have a cruising range of more than 50 miles. Adults are less than a quarter-inch long and have grooved wing covers. Their other prominent feature is a huge, curved snout that runs almost half the length of the body.

Today, Pierce is still fighting weevils, working with a Phoenix-based group of USDA researchers on a project which examines various formulations of malathion, a potent insecticide, in microencapsulated formulations.

"The aim is to reduce the number of applications," Pierce said. "We're looking for longer residual activity so it will last two weeks, instead of one, which cuts the number of applications in half."

If the project is successful, she said, it will slice application costs in half and save about $30 million across the Cotton Belt each year.