Federal Government Approves Release of Non-Native Weevil in California to Combat Invasive Thistle

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AP | 9/18/2019 | Via Capital Public Radio

Federal officials have approved turning loose a non-native insect to feed on an invasive thistle that sprouts in everything from rangelands to vineyards to wilderness areas, mainly in the U.S. West.

The U.S. Department of Agriculture said Tuesday it will permit use of the weevil native to Europe and western Asia to control yellow starthistle, which is from the same areas.

Yellow StarthistleBrad Hanson, UC Cooperative Extension weed specialist at UC Davis, says yellow starthistle thrives in part because of its prickly spines.

“So it’s not very palatable to any livestock, especially once it’s started to flower, and it’s toxic to horses. So oftentimes the other grasses and more palatable plants are grazed and the starthistle persists and is sort of the only thing left,” he said.

The spines also help the weed spread as it hooks on to vehicles, farm and lumber equipment, animals and clothes. Hanson says yellow starthistle can be managed on a small scale with chemicals, but that method just doesn’t work with the scale of infestation in the state.

“It’s difficult to control economically on the millions and millions of acres of rangelands or non-agricultural lands that are sort of minimally managed,” he said.

The U.S. Agriculture Department said yellow starthistle entered California before 1860 and is now one of the state’s worst pests. Idaho, Oregon, and Washington also have heavy infestations of the thistle that’s been found in 41 states.

The USDA says its been testing the weevils at a lab in Albany, California, to make sure they won’t attack native plants or cause some other environmental damage.

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