From RiversEdge West via The Grand Junction Daily Sentinel:
Tamarisk trees, those green bushy plants seen along waterways, have been turning brown across the county thanks to a special beetle used to control the invasive species.
Ben Bloodworth, Tamarisk Beetle Program coordinator with RiversEdge West, sent out a note Monday responding to social media posts from local people wondering why they were seeing so many browning tamarisk plants.
“These are tamarisk trees, or salt cedars, and the phenomenon is currently so pervasive here in the valley that folks are starting to wonder about it on social media,” Bloodworth said. “So, before you blame anyone for over-spraying, or the hot, dry air of June, let’s chat about the millions of little beetles that live in the valley with us.”
According to Bloodworth, tamarisk, which is native to Asia and the Mediterranean, became such an environmental and economic problem in the western United States that the U.S. Department of Agriculture (USDA) decided to research and release a biological control agent to address the issue.
“Biocontrols are natural ‘predators’ that feed on plants in their native ranges but are not found in the U.S.,” Bloodworth said. “In 1987 the USDA began a program to find natural enemies of tamarisk and see if they could live and feed on tamarisk in North America without feeding on anything else.”
Out of hundreds of candidate species, the tamarisk beetle was found to be the most successful. It was found to only feed on tamarisk and not any other species of plants. So the USDA began releasing it, including in Moab, Utah, in 2001. From there the beetle spread up the Colorado River to Mesa County.
“Since tamarisk beetles survive on tamarisk as their only food source, they were never intended to eliminate the invasive plant,” Bloodworth said. “Rather, they were released to help control the spread of the plant and reduce the amount that land managers must remove by other, more costly means.”
The small green beetles, when there is a large enough population, can defoliate a large amount of tamarisk in just a few weeks. Left behind are the orangish brown remains of the formerly green tamarisk.
“The populations ebb and flow with available tamarisk and some years we have almost no tamarisk beetles anywhere,” Bloodworth said. “As you may have noticed by all the brown tamarisk, this is not one of those years!”
Counterintuitively the brown, dead tamarisk is actually less of a fire danger than the green plant, Bloodworth said. It may initially, for a few weeks, be more susceptible to catching fire, but once it has dropped its leaves it is actually less of a fire risk, according to Bloodworth.
“The brown trees may not be pretty, but they do provide for opportunities to restore native vegetation alongside our rivers,” Bloodworth said.