Better beetle sought for salt cedar control

June 27, 2006

BUSHLAND - Beetles from Uzbekistan are more prolific salt cedar eaters than beetles from Greece. At least that's what Texas Agricultural Experiment Station researchers hope.

Uzbekistan salt cedar beetles being released by the Experiment Station's entomology department are the same species as those released on the salt cedar stands near Lake Meredith. They are just from a different collection point, said Vanessa Carney, Experiment Station entomology research associate.

Researchers first looked at latitude and longitude to find the beetle they thought would be best suited to this region, and they came up with salt cedar beetles from Posidi, Greece, Carney said.

"Because some of the releases in other states haven't been successful, we're starting to think it may be more complicated than that," she said. "These beetles from Uzbekistan seem to be most suited to our climate at the same latitude and longitude."

At the Meredith site, the Posidi beetles released in 2004 have made it through two winters and had two summers of success, Carney said. However, because of an early warm-up followed by a cold spell, they seem to be less prolific this summer and haven't exploded in numbers.

Dr. Jerry Michels, Experiment Station entomology research project leader, and Carney are making new releases of the Uzbekistan beetle this year in the heavy salt cedar stands on private land north of Borger. The new site was selected because of its remote location and because it is not subject to other control methods, such as fire and chemical treatments, Carney said.

A total of 25 egg masses have been released at three different sites, all within cages, Carney said. While the Posidi beetles are approved for open release, the Uzbekistan beetles have not been approved by Animal and Plant Health Inspection Service for open release so they must be enclosed in tents.

The beetles being released into the confined salt cedar trials were provided by Dr. Jack DeLoach with the U.S. Department of Agriculture-Agricultural Research Service at Temple, where other studies are being done.

Each egg mass had 10 to 30 eggs. Another 60 adults were released between the three sites, Carney said. Each egg will go through three larval stages, during which time they feed on the salt cedar, before they drop into the ground and emerge a week later as a beetle.

"Almost immediately they will start mating and will live for about 30 days," she said. "We're doing more extensive work on those figures in our lab at Bushland. We want to determine how many eggs they lay, the life cycle times and how many batches of eggs they lay in a lifetime."

Damage is what the researchers want to start seeing, Carney said. The Posidi beetles at Lake Meredith defoliate small branches, but the damage hasn't been widespread. So far, the Uzbekistan beetles haven't been here long enough for the scientists to gauge what they can do.

"They just came in May and the first year we don't expect to see major damage," she said. "But they may defoliate the trees within the cages. We were warned that it will go quickly, and we may run out of food within the tents."

Michels and Carney said their Texas salt cedar beetle work is part of a larger study that is looking at beetles from Fukang, China; Crete, Greece; Tunisia, Africa; and Turpan, China.

These four strains of beetles will be released in various sites throughout the U.S., with emphasis on establishing them at two Texas sites, and in Colorado, Wyoming, Utah and Nebraska.

"What we want to see is the differences of these strains at different latitudes," Michels said. "People have released a strain here or a strain there, but what we want to do is release all of these strains at each site and maybe then be able to make some decisions that are backed up by research."

Ultimately, the study should help determine which strains are adapted to which latitude, he said. The Crete strain was released from Wyoming to South Texas and did not work everywhere. At the same time, some of these strains are new and haven't been tested anywhere.

This new widespread study will begin once researchers receive approval from USDA's Animal and Plant Health Inspection Service, Michels said.
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Texas A&M AgriLife Communications

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