DALLAS — An “early warning” trap system to predict a damaging moth on pecan trees goes into 25 test sites in Texas orchards this spring.
While in very short supply this year, the traps will be a new and inexpensive way for growers to monitor this pest before it damages the crop.
Dr. Allen Knutson, a Dallas-based entomologist with the Texas Agricultural Extension Service, will direct the second year of trials using a newly identified sex pheromone to monitor flights of pecan nut casebearer moths, the most damaging of many insects that assault pecans.
Traps will be located in every pecan-producing area of the state, plus one in Mexico near Monterrey. They also will be widely used by commercial pecan growers in West Texas and New Mexico.
“We believe the casebearer pheromone trap will be an important tool for producers in managing this pest,” said Knutson. “While a well- timed insecticide treatment controls the pest, we know from experience that overuse of insecticides for casebearer in the spring can kill beneficial insects that feed on aphids, mites and leaf miners.”
Knutson predicted the pheromone traps will be on the market for growers in 1996. Texas is second only to Georgia in pecan production, accounting for 20 percent of the nation’s pecans. The 1994 pecan crop was valued at $49 million.
Led by Knutson, a U.S.-Canadian research effort identified the sex attractant chemical the female releases to attract the male. The team then isolated and synthesized the pheromone and used it to lure the unsuspecting male moth into sticky traps. Finding male moths in the trap tells growers that females are flying and infesting pecans with eggs.
The larva, or worm, of the pecan nut casebearer, Acrobasis nuxvorella, burrows into the shell and eats the immature nut before it’s fully developed.
“Many pecan growers in Texas have seen the egg and larval stages, but the adult or moth stage is much more elusive,” said Knutson, director of this biointensive research.
“Very few producers have ever seen the moth. But by monitoring their flights, growers should have an early warning system to know when to begin scouting the orchard for infestations of eggs and larvae.
“Finding moths in the trap doesn’t mean we should spray the orchard,” cautioned Knutson. “It means — go look for eggs on the nutlets.”
Karin Davidson, president of the Western Pecan Growers Association, agreed.
“The first flight of the insect in early spring inflicts the worst damage,” she said. “We only have a two- or three-day window to spray. And if you miss the window, it’s all a waste of chemicals, time and labor. It’s possible to lose 40 percent of a crop from this insect.”
Pheromone-baited traps are a common tool in monitoring other pests.
Since each female produces a tiny amount of pheromone, hundreds of female moths were needed for the research. Efforts to rear the casebearer on an artificial diet were not successful.
“They’d rather die than switch,” Knutson commented. “And they did. If it wasn’t a real pecan, they weren’t interested.”
That sent Knutson into North Texas cemeteries, parks and roadsides in search of unsprayed pecan trees. There he collected pecans infested with casebearers and successfully reared them to adulthood.
Working with Knutson are Dr. Jocelyn Millar of the University of California at Riverside and Drs. Gerhard and Regina Gries of Simon Fraser University in British Columbia. Millar and both Grieses are recognized scientists in the area of insect pheromones and have both the specialized knowledge and sensitive equipment for pheromone identification and synthesis.
For three years, Millar did chemical extractions of moths Knutson shipped to his California lab. Knutson described it as “making a moth soup and then looking for the pheromone floating in there somewhere.” Millar then sent possible pheromone compounds back to Texas where Knutson placed them in traps, hoping they would attract moths.
Millar disclosed the chemical structure in December to a national meeting of entomologists. This makes the pheromone structure public knowledge and available to anyone who wants to market it.
“Now that the chemical structure is known, any organic chemist could reproduce it in a few weeks,” Millar said. “We hope soon that some companies will begin making it for growers to buy.”
In 1994, the New Mexico Department of Agriculture placed 200 traps in the Mesilla Valley to determine if the casebearer was present. More than 15,000 acres of pecans are grown in this lush valley with very little insecticide use. Results confirmed for the first time that the casebearer was present. The insect was first found in metropolitan El Paso in 1988, alerting nearby pecan growers, in both Texas and New Mexico, to its possible movement into area commercial orchards.
“Local growers have shown a lot of interest in using these traps to detect and monitor the casebearer in their orchards,” said Charlie Payne, Extension entomologist in El Paso. “The new pheromone traps will be used this year in nearly all commercial orchards in El Paso County.”
Knutson believes monitoring the casebearer with pheromone traps promises to be an essential part of a growing integrated pest management (IPM) approach in pecan production. The need for insecticide can be more reliably determined when pheromone traps are used with orchard scouting.
“It’s very important to remember this is a tool to detect moth flight and not a treatment for the insect,” cautioned Knutson. “Using the pheromone trap in combination with the Texas A&M computer prediction of expected egg-laying activity should give growers two powerful tools for combatting this pest.”
The Western Pecan Growers and Texas Pecan Growers funded the initial research. The Texas Department of Agriculture and Texas Pest Management Association is funding a project to evaluate and implement the use of pheromone traps in Texas.