Group hopes to eradicate arundo from Santa Margarita River

| Tuesday, September 19, 2000 10:00 PM PDT ∞

DAVE DOWNEY
Staff Writer

TEMECULA ---- A new group is preparing to spray herbicide along Murrieta Creek and the Santa Margarita River next month, launching a five-year campaign to rid streams in the 772-square-mile watershed of invasive nonnative plants.

The Santa Margarita and San Luis Rey Watersheds Weed Management Area, a public-private partnership created in March, is focusing on arundo and tamarisk plants, commonly known as giant reed and salt cedar, respectively, in the $70,000 effort, officials said Tuesday.

The arundo is of particular concern because it sucks up three times as much water as native plants, poses a fire danger, threatens to make floods worse, and crowds out plants that house endangered animals.

"The only way we're going to eradicate it is to start spraying, and spray from the top down," said Judy Mitchell, the coordinator for the Mission Resource Conservation District, which takes in Fallbrook, Rainbow and Bonsall.

The district is the public portion of the partnership. The private member of the team is DENDRA, a northern San Diego County biological consulting firm. The partnership expects to receive a permit to spray in areas inhabited by endangered species from the state Fish and Game Department today.

Agencies and landowners downstream on the Santa Margarita want to get rid of the bamboolike shoots that sport cornlike leaves and grow to more than 20 feet tall, Mitchell said. But downstream eradication efforts won't do any good if arundo plants wash down from upper reaches of the drainage and recolonize areas.

So the partnership is starting out in southern Riverside County, targeting sporadic stands of arundo along the banks of Murrieta Creek in Temecula and along the Santa Margarita River southwest of Temecula and in northern San Diego County.

"The arundo is getting a little dry; it's starting to go dormant," biological consultant Jason Giessow said. "So this is exactly the time you want to be spraying."

As well, Giessow said, the nesting season for birds is over, so there is no danger that the herbicide will harm the endangered least Bell's vireo and the California coastal gnatcatcher, both of which rely on Santa Margarita habitat.

It is better to spray than to cut, he added. The herbicide gets down into the roots and kills the plants. But cutting promotes rapid regrowth the following spring, Giessow said, and the little plant pieces left over from cutting tend to wash downstream and sprout new plants.

"Just about any piece of the plant can grow," said Giessow's wife and business partner, Jesse.

It won't be the first time that exotic invaders have been sprayed in Murrieta Creek.

The Riverside County Flood Control District regularly mows the creek bed between Rancho California and Winchester roads each fall to reduce the stream's flood threat to low-lying areas such as Old Town Temecula. Then, said Chief of Operations Coen Couwenberg, the district rips out arundo plants with an excavator and treats the stumps with herbicide.

Still, Couwenberg said, "That stuff just comes back with a vengeance."

Giessow said the new strategy of spraying first should work much better; it has a track record of killing 95 percent of the plants.

Mitchell added that the Weed Management Area project will not conflict with the flood control district's mowing. She said the spraying campaign will be south of there, covering 2 acres of Murrieta Creek between Old Town and the stream's confluence with Temecula Creek. The rest of the 33 acres to be sprayed are on the main stem of the Santa Margarita and along Rainbow Creek in San Diego County.

The worst concentration of arundo is on Camp Pendleton Marine Corps Base, but the military is footing the cost of eradication efforts there, Mitchell said. Upstream, arundo stands span about 300 acres. The tamarisk plants grow mostly in the drier upper sections of the Santa Margarita and its tributaries in Riverside County.

This fall's campaign targets the Temecula area, Rainbow Creek and Fallbrook. The spraying will cost $4,000 to $5,000 per acre, Mitchell said.

Officials hope to nip this invader in the bud, long before it infests the Santa Margarita watershed on the scale that it has in the Santa Ana River in northern Riverside County and southern San Bernardino County. There, the exotics have crowded out cottonwoods and willows on the way to colonizing 10,000 acres.

Arundo was introduced in this country from the Mediterranean region.

Contact Dave Downey at (909) 676-4315, Ext. 2621, or downey@nctimes.com.

9/20/00

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