A crew Friday sprayed a herbicide on water hyacinth clogging part of the lower Tuolumne River.
The spraying in the Fox Grove area, where Geer Road crosses the river, is part of an increased effort against the aquatic weed in the Sacramento-San Joaquin Delta and some of its tributaries.
The state last week announced a $4 million boost in funding because drought has made the problem worse with low flows and warm water. Hyacinth forms mats that can interfere with boating and fish habitat.
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“My constituents in the area have been besieged by this non-native plant, which has all but shut down boat traffic and other commerce in the south Delta,” state Sen. Cathleen Galgiani, D-Stockton, said in a news release.
She helped secure the $4 million, which is being added to a $9 million annual program at the California Division of Boating and Waterways.
Crews on boats are spraying glyphosate or imazamox on the hyacinth and another aquatic weed called spongeplant. A total of 19 sites on the Tuolumne are being treated this year, from its confluence with the San Joaquin River on up to the La Grange area, where a dam blocks further spread.
The Merced and San Joaquin rivers also are being sprayed up into the lower Sierra Nevada foothills. The Stanislaus River has not had so much of a problem, thanks to higher flows required for fish.
Hyacinth arrived from South America more than a century ago, according to the state agency’s website.
“This extremely prolific aquatic invasive plant can double in size every 10 days in hot weather and can quickly become a dense floating mat of vegetation up to 6 feet thick,” it said.
Officials said hyacinth can be contained with spraying and mechanical means but never wiped out.
Bee staff writer John Holland can be reached at firstname.lastname@example.org or (209) 578-2385.