UGA Researching Ways to Control Pests that Damage Pecan Tree Roots
By Clint Thompson
University of Georgia, College of Agricultural and Environmental Sciences
A University of Georgia researcher is using two news traps and the beetle's sex drive to trap and control the pest that damages the roots of pecan trees.
Prionus root borers, the larval stage of the beetle, damages pecan tree roots by depriving trees of essential water nutrients. This makes them vulnerable to heavy winds. The larvae can also move through the soil and feed on an irrigation system if they encounter a pipe between pecan roots.
Recent research, however, by University of Georgia entomologist Jim Dutcher may lead to successful control methods. Dutcher is partnering with industry cooperators to develop an integrated monitoring and control method.
"(Root borers) have been a problem since I've been here and that has been more than 30 years," said Dutcher, a UGA College of Agricultural and Environmental Sciences entomologist based in Tifton. "We really didn't have many control options until now."
In 2006, the sex pheromone that the female beetles use to attract mates was discovered by scientists at the University of California-Davis. Field trials in Tifton and across the United States found that many species of the prionous root borer, including those that attack Georgia pecan trees, also are also attracted to the pheromone.
Dutcher and numerous cooperating pecan growers in south Georgia are studying the use of beetle traps baited with the pheromone as a monitoring device and as a part of an integrated control method. Currently, a panel trap baited with a pheromone lure works well for male beetles. Female beetles are trapped with a generic pitfall trap baited with alpha-pinene.
This year, a new trap will be used to attract males and female beetles. The new trap includes a pail to collect the beetles, wooden beetle guides to direct the beetles toward the pail, a pheromone lure wafting in the air to attract the male beetles, a set of plastic panels to stop beetles that fly to the lure and a plastic cover to keep the rain out.
The top panels and cover of the trap are made by modifying a panel trap manufactured by Alpha Scents, Inc. Beetles crawl or fly towards the trap and fall helplessly into the pail. The inside of the trap is coated to prevent the beetles from crawling out.
"New traps baited with pheromone will collect males and new traps baited with alpha-pinene will collect females," Dutcher said.
Numerous field trials in pecans and other crops conducted by entomologists across the U.S. have found that the pheromone-baited traps can attract beetles from as far as 800 feet away. In Georgia pecans, one trap will collect several hundred beetles per week during the peak emergence period in May and June.
"The utility of the traps as a monitoring tool is a great improvement over the old light trap method that has been used for the past 30 years," said Dutcher, who noted that the traps may also be effective as a part of an integrated beetle control method.
Two possible methods are mating disruption where an orchard is inundated with pheromone and males cannot find mates, or mass trapping where male beetles are trapped over a large plot of acreage with a matrix of evenly spaced traps.
Dutcher and his team of pecan growers are also testing chemical control methods where beetles are monitored with traps and the soil is treated to control the beetles before they lay eggs near the tree trunk and roots. Research is under way to incorporate the new trapping system into pecan pest management in Georgia pecans.
Pecan orchards with high root borer infestations have been reported across south Georgia from Cordele to Leesburg and from Tifton to Waycross.
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