First Biological Control Agent For Saltcedar Released

By Kathryn Barry Stelljes
July 8, 1999

TEMPLE, Texas, July 8--U.S. Department of Agriculture researchers will place about 3,000 eggs of Chinese leaf beetles in experimental field cages in six states as the first step in a biological control program for the invasive weed saltcedar. The trees, which can grow up to 30 feet tall, infest more than 1 million acres along rivers and streams throughout the West.

"The leaf beetles eat only Old World species of saltcedar," said C. Jack DeLoach, an entomologist with USDA's Agricultural Research Service. Over the next few weeks, he and colleagues will place beetle eggs or larvae on caged saltcedar plants at sites in California, Colorado, Nevada, Texas, Utah and Wyoming. DeLoach, based at the ARS Grassland, Soil and Water Research Laboratory in Temple, leads the biological control project.

“Saltcedar was brought into the U.S. in 1837 to protect streambanks from erosion," DeLoach said. "But no one realized that, without natural enemies, saltcedar would crowd out plants crucial to wildlife." The trees also degrade wildlife habitat, by increasing soil salinity, changing streamflows and increasing wildfire frequency.

USDA’s Animal and Plant Health Inspection Service today authorized permits, with concurrence from the U.S. Fish and Wildlife Service, for ARS to release the beetles into cages at selected sites across the western U.S.

DeLoach said that this is the first time biocontrol scientists have targeted a weed that can be important to an endangered animal--namely, the southwestern willow flycatcher, Empidonax traillii extimus. These birds nest in saltcedar in some locations where the trees had crowded out and replaced their native willow nesting sites. For this reason, ARS will conduct one year of field experiments during which the beetles will remain in cages. In addition, no beetles will be released in any areas near nesting flycatchers without approval from the U.S. Fish and Wildlife Service.

For the field tests, DeLoach and colleagues will erect 10-foot-square cages over existing saltcedar infestations along rivers and streams near Bishop, King City and Woodland, Calif.; Pueblo, Colo.; western Nevada (Lovelock, Schurz and Fallon); Seymour, Texas; Delta, Utah; and Lovell, Wyo. Diorhabda eggs will be placed on the saltcedar so the insects will have a food source upon hatching. Researchers will monitor the behavior of the beetles in the cages.

“Diorhabda is an ideal biological control agent,”said ARS ecologist Raymond I. Carruthers. The beetle was tested extensively in China and in ARS quarantine facilities in Temple. Researchers have found no plants other than saltcedar on which the beetles feed and reproduce, and no native saltcedar relatives occur in the U.S. Carruthers leads the Exotic and Invasive Weeds Research Unit at the ARS Western Regional Research Center in Albany, Calif.

“There has been some concern that the beetles will defoliate the saltcedar so quickly that the flycatchers will not have nesting areas,” said Carruthers. “We do not expect this to happen. Biological control is a gradual process, and we expect willow trees to reestablish as saltcedar is slowly reduced,” he said.

When the beetles are ultimately approved for release outside the cages, they should spread out several hundred feet per year to infest other saltcedar plants adjacent to previously caged areas. Beetles would have to be collected and released at new sites to enhance saltcedar control.

The biological control program for the saltcedar is just one of many steps USDA is taking to address the growing environmental and economic threat of invasive species. As part of a recently created Invasive Species Council, USDA , the Departments of Interior and Commerce will help draft a federal strategy to combat invasive species. The Administration’s fiscal year 2000 budget proposal also includes more funding to fight these invasive species in the new millennium.

Scientific contact: C. Jack DeLoach, ARS Grassland, Soil and Water Research Laboratory, Temple, Texas, phone (254) 770-6531, fax (254) 770-6561, deloach@brc.tamus.edu; Raymond I. Carruthers, ARS Exotic and Invasive Weeds Research Unit, Albany, Calif., phone (510) 559-6127, fax (510) 559-6123, ric@pw.usda.gov.