Invasive weeds mar rangeland

By Chris Caskey, The Union Democrat October 22, 2012 09:43 am

Local agriculture officials are working to help manage a handful of invasive plants that could be problematic for ranchers.

Tuolumne and Calaveras county agricultural commissioners are concerned about the increased prevalence of Klamath weed, as well as grasses known as Medusahead and barbed goathead. All three non-native plants are found on local rangeland and can in some cases be harmful to the livestock that feed on them.

Also known as St. John’s wort, Klamath weed is a flowering shrub that is toxic to horses and cattle and invasive throughout California. Tuolumne County Agricultural Commissioner Vicki Helmar said a beetle known as the Klamath weed beetle is used as an agent to control the plant, and it was successful for a number of years.

But by eating most of the plants, the beetles cut down their food source resulting in fewer beetles, Helmar said. Ideal rain conditions over the past three years have led to increased Klamath weed with a less robust defense.

“The beetle population is so low, it’s just not able to control the weed.” she said. “It will take a few years before we can increase” their numbers.

Medusahead and barbed goathead both grow amidst area range grasses. While they’re not poisonous, those weeds degrade the quality of the overall grassland as food. Because they grow among good grasses, they’re very difficult to control.

“They will take over rangeland,” she said. “It’s important for our growers and producers to start controlling this. It out-competes some of our good rangeland grasses.”

The county and University of California Cooperative Extension are hosting a workshop Oct. 31 at Tuolumne County’s emergency operations center, 18440 Striker Court, Sonora. It will run from 8:30 a.m. to noon, and it will include talks on the issue.

In Calaveras County, Assistant Agricultural Commissioner Kevin Wright said he’s also seeing the “same problems” with those plants. He said the department will try to educate private ranchers and farmers about the plants and ways to keep them from spreading.

“Some of these are well-established, beyond the point where it’s a localized infestation,” Wright said.