Arkansas Valley: Tamarisk control

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Officials are getting ready to release tamarisk leaf beetles in several areas in the Arkansas River Valley next week with hope that the critters will establish well and control tamarisk. Here’s a report from Chris Woodka writing for The Pueblo Chieftain. From the article:

The beetle Ñ technically, diorhabda carinulata Ñ was released in Utah several years ago and migrated into Colorado. It is thriving in every river basin on the Western Slope, but has been slow to take hold in the Arkansas Valley, which is the most heavily infected region of the state when it comes to the invasive trees. This week, thousands of beetles were harvested along the Dolores River in the Southwest corner of the state for release next week on Fountain Creek and other tributaries, and at Boone, Fowler, Rocky Ford, Two Buttes, Granada and Holly.

Bean and his staff will also be checking up on beetles that have established themselves on Beaver Creek in Fremont County. There is also a small population established below Pueblo Dam as the result of another strain of beetles from western China tested by the Bureau of Reclamation several years ago. “There are already major efforts to remove tamarisk in the Arkansas Valley, and the beetles are a supplement to those other efforts,” Bean said. Some theories speculated that the beetles, from Kazakhstan, would have trouble thriving at lower latitudes. Kazakhstan lies entirely above the 40th parallel, while Colorado is further south, resulting in fewer hours of daylight during the summer months. Still, in the Dolores basin, there are millions of beetles that have knocked back thousands of acres of tamarisk. The beetles have also decimated tamarisk in the Colorado, Green and Yampa basins, Bean said…

One of the reasons for next week’s releases will be to track how well the beetles can establish themselves in the Arkansas River basin…

The beetles will eat the leaves – and more importantly the flowers which contain seeds – of the older tamarisk as well. This makes them an effective biocontrol for the trees, but not a way to eliminate tamarisk altogether, Bean said. “In the long run, if they’re established in the basin, we’ll have a background population that will keep tamarisk under control,” Bean said.

More coverage from the Ag Journal (David Vickers):

[Dr. Dan Bean, the state’s top expert in using insects to control invasive plant species like tamarisk] manages the Colorado State Department of Agriculture’s Plant Industry Division Insectary at Palisade. He spent three days, July 7-9, working along the Apishipa and Purgatoire rivers in Las Animas County to release beetles that will devour tamarisk, also known as salt cedar. Patty Knupp, a private land and wildlife biologist, said 1,000 beetles were released July 7 in two locations along Chacuco Creek, a tributary of the Purgatoire River. On July 8, four more releases of beetles were conducted along the Purgatoire River and two releases were made on the Apishipa River. Then, on July 9, the tamarisk eating beetles were released on the main stem of the Arkansas River near Fowler…

Ants and Asian ladybugs are natural predators of tamarisk beetles and can be particularly tough on a population.
“We’ve found that the beetles don’t do especially well below the 38th parallel,” she noted. “The number of daylight hours have an impact on whether they flourish.” But there have been some fairly significant success stories, especially with aerial application of herbicide. Since 2005, more than 2,000 acres along the Apishipa River drainage have been sprayed.

More Coyote Gulch coverage here and here.

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