Giant reed prompts major concern

| Saturday, February 5, 2000 10:00 PM PST ∞

HARRY BROOKS
Staff Writer

BONSALL ---- It's a jungle out there, or so it appears with the bamboo-like Arundo donax plant taking over large stretches of the San Luis Rey River's winding 50-mile path that begins above Lake Henshaw and ends at Oceanside Harbor.

And the proliferation of the voracious plant is a big concern among environmental scientists who monitor the river, said Valerie Mellano, a water-quality adviser in San Diego County for the University of California Cooperative Extension Service.

"Arundo poses a real threat," said Mellano, who earned a doctoral degree in plant pathology from UC Riverside in 1988. "It provides no food or nesting habitat for animals and spreads aggressively, crowding out beneficial plant species. It can grow up to 4 inches a day and gets over 14 feet high."

Mellano, who lives in Fallbrook, said numerous efforts are under way to eradicate the persistent plant throughout Southern California, but little has been done to battle the advance of arundo in the 558-square-mile San Luis Rey watershed.

That could change this month when the UC Extension Service begins an arundo education program for landowners along the watershed, she said.

The program will include field trips to increase participants' awareness of various non-native plant species that are detrimental to riparian areas in the watershed. Information on safely eradicating them also will be provided, Mellano said.

Those plants also include salt cedar (a species of tamarisk) and pampas grass, but arundo will be the program's primary focus.

"Salt cedar and pampas grass are a concern, but by far the arundo is a bigger problem there," said Andrea Souther of the Mission Resource Conservation District in Fallbrook.

Mellano, coordinator of the San Luis Rey Watershed Council, said the basic method of safely ridding arundo from infested areas involves cutting the plant as low to the ground as possible and applying a herbicide to kill its roots. She said the most commonly used herbicides contain the same basic ingredients as Roundup, a commercial brand commonly used on residential yards to eliminate weeds and unwanted vines.

"Right now, the arundo is winning," she said, referring to the invasive species' spread along rivers and creeks in Southern California. "It would cost millions (of dollars) to get rid of it.

"It comes to about $7,000 an acre. The process is very manual and that makes it very expensive."

Mellano said there is no current estimate on the amount of arundo that exists along the San Luis Rey River but noted the plant has caused heavy damage.

The most obvious, she said, occurred during major storms in 1993 and 1995 when flows of arundo, which had been uprooted by strong currents, choked the San Luis Rey River's flow under bridges at Camp Pendleton. The increasing pressure of the rising water caused some of those bridges to break apart.

Arundo donax, the scientific name for the plant that is commonly called "giant reed," was imported from Asia to Southern California in the 1820s to help stem erosion along waterways and provide thatch for structures, Mellano said.

While generally viewed as an invasive pest, the plant now is the source of almost all reeds for musical instruments and is also used in making baskets, wood bird cages and similar items. Mellano said arundo possibly could be harvested for use in fiberboard manufacturing.

However, the plant's adverse qualities far outweigh its benefits, environmental scientists say.

Ironically, arundo now is considered a prime culprit in causing erosion, the state Department of Fish and Game states in a pamphlet titled "Arundo ---- Streamside Invader."

The plant's shallow roots are undercut easily by stream flow, causing them to break away from the bank and take soil with them, the pamphlet notes.

Clumps of arundo then float downstream, causing clogs. The remainder often comes to rest along on the bank downstream to re-root and start another growth of the aggressive plant.

"What we need to establish is an overall plan that moves downstream in getting rid of it," Mellano said. "That way you don't get the plant reintroducing itself by coming in from upstream after you clear areas further downstream."

When arundo growth begins expanding along rivers and in shallow streams, the highly flammable plant not only displaces native vegetation, but also transforms the area from a fire break to a fire hazard, the Fish and Game pamphlet states.

Making matters worse, the stalk of the plant is sturdy, allowing arundo to commonly survive fires that consume other vegetation. That makes it easier for the plant to spread after a fire, Fish and Game says.

The plant also "has a huge appetite for water," extracting quantities that often are needed to support a variety of plant and animal life along waterways, scientists say.

For more information on the UC Extension Service's arundo education program, call Diane DeJong at (858) 694-2849 or (760) 723-5316 or Valerie Mellano at (858) 694-2845 or (760) 728-1332.

2/6/00

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