Imported beetles prove effective in controlling invasive saltcedar
Since 2006, a steadily growing army of tiny beetles from the homeland of invasive saltcedar trees—Crete and Tunisia—have been providing biological control by slowly eating their way through saltcedar thickets, said Dr. Allen Knutson, Texas AgriLife Extension Service entomologist at Dallas.
"Most Texans who spend time along West Texas' rivers, streams and reservoirs recognize saltcedar," Knutson said. "It was introduced into the United States as an ornamental plant in the early 1800s, but unfortunately it escaped to become an invasive species. Today, dense thickets of saltcedar choke out desirable vegetation, use large amounts of groundwater and increase the risk of flooding as trees narrow the river channel."
Saltcedar infests some 500,000 acres in Texas, Knutson said. He added that herbicides are effective but very costly. Saltcedar arrived in the United States without its natural enemies, he said. Biological control reunites the saltcedar with its natural enemies, limiting the trees' invasive nature.
"We have been working to establish the leaf beetles for biological control of saltcedar since 2006," he said. "To date, we have collected and released over 800,000 beetles in 15 West Texas counties. This year, we are starting to see the area-wide impact of this effort as beetles have defoliated saltcedar thickets along miles of the Rio Grande, Pecos, Colorado and Upper Brazos Rivers. Once established, these 'bio-beetles' should persist without the need for additional releases."
He said the small beetles and their larvae eat saltcedar leaves. Without leaves, the trees slowly starve to death. "Not many of these trees are 'graveyard dead' yet, but over time, our research and experience has shown canopies will die back and in some sites, trees will die as the beetles return each year and defoliate the trees."