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The Tamarisk Beetle Program is turning trees brown in the valley

Published: Jul. 6, 2021 at 9:18 AM MDT
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GRAND JUNCTION, Colo. (KKCO) -You may have noticed brown trees that were bright green a few weeks ago. These are Tamarisk trees, or salt cedars.

Tamarisk is an invasive plant from Asia and the Mediterranean that appears in many Western waterways in the U.S. The U.S. department of Agriculture decided to research and release a biological control, biocontrol, agent to address the environmental and economic impact the plant has.

Biocontrols feed on plants in their native ranges but are not found in the U.S. In 1987 the USDA began a program to find natural enemies of tamarisk and see if they could live and feed on the plant without feeding on anything else. Out of 300 organisms, the tamarisk beetle was the most successful. So, tamarisk beetles were released to help control the spread of the plant and reduce the amount that land managers must remove by other, more costly means.

Before being released, tamarisk beetles were tested to ensure they would not eat any non-target species and will only eat tamarisk. After more than a decade of testing, tamarisk beetles were released on the Colorado River in 2001 and moved up into the Grand Valley a few years later.

RiversEdge West is a Grand Junction-based nonprofit dedicated to the restoration of riverside ecosystems. It has been monitoring the movement and impacts of the tamarisk beetle since 2007 but has never released the beetle. Its Tamarisk Beetle Monitoring Program maps the tamarisk beetle’s movement and connects land managers with information on the beetle and its potential impacts.

Tamarisk beetles are green with yellowish stripes and are similar in size to a ladybug. They defoliate tamarisk trees turning green trees to an orangey-brown in a matter of weeks. The beetle lives for about five or six weeks and spend most of that time as a small black caterpillar-looking larvae that does most of the feeding. There are three to four generations of beetles here in the valley each summer before they go into hibernation beneath the trees during the winter.

The green vegetation on the riverbanks turning green does not mean there is a higher risk for wildfire. the dead branches of tamarisk after defoliation are less flammable than the green vegetation. Green tamarisk is explosive when it burns and grows back immediately after a fire. Experiments have shown that trees repeatedly defoliated by the beetle burn with a lesser flame length.

While the brown trees may not be pretty, they provide opportunities to restore native vegetation along the rivers. To learn more, visit www.rivesedgewest.org.

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