New Delta invader threatens to clog waterways, pumps

December 22, 2011 By Mike Taugher

WALNUT CREEK, Calif.-An invasive weed just now taking hold in the Delta could clog water delivery pumps and marinas on a scale never seen here before, but state officials say they are nearly hamstrung in trying to deal with it.

Few have even heard of the new threat, South American spongeplant, because it has been found only recently and in just a few places, all in California.

But what they have seen so far has alarmed experts.

"Your jaw drops at what's going to happen," said Lars Anderson, a weed scientist at the U.S. Department of Agriculture's agricultural research service. "The weeds don't stop."

Anderson and other experts say that if it is not controlled or eradicated, spongeplant could become a bigger problem than water hyacinth, one of the world's most troublesome water weeds. The state spends more than $2 million a year to control the hyacinths, established in the Delta for several decades, so water delivery pumps can work and boats can move about.

The spongeplant, like water hyacinth, floats on the surface and threatens to clog channels with impenetrable masses of weeds.

But because it is smaller, spongeplant could spread more easily and get deeper into pumps and water works. It is a prolific seed-bearer, unlike water hyacinth, meaning it could be even harder to eradicate, experts say.

"I think we're going to see a large expansion of spongeplant in the next three to five years if nothing is done," said Anderson. "It's very serious."

Although the invasion was detected early, weed control agencies say they lack the legal authority to spend state money to attack it.

Drifting in a small boat toward a stand of tules at Decker Island, between Antioch and Rio Vista, state Department of Food and Agriculture weed biologists David Kratville and Jonathan Heintz spotted some spongeplant among the tules, hyacinth and several other kinds of weeds.

"You can see how densely packed it is," Heintz said.

Kratville separated a small floating seedling from a larger mat of weeds and explained how easily it could float away and spread.

For now, large mats of spongeplant can be removed fairly easily by scooping it out of the water with heavy equipment. But as it becomes established, herbicides may be needed.

If it does become established, how bad will it get?

"We don't want to find out the hard way," Kratville said.

Named for the spongy leaves that keep them afloat, spongeplants likely made their way into the Delta from backyard ponds containing the ornamental plant. Although they are the newest intruder in the West Coast's largest estuary, they carry a practical threat - the Delta is a water source for two-thirds of California and serious weed infestations can clog pumps and canals, making it more difficult and expensive to keep water flowing to farms and cities.

Spongeplant was first detected in California in 2003 when a dense mat choked a pond in Redding. In 2007, it turned up in the Delta near Antioch but disappeared after a rainstorm.

It reappeared in 2009 in the western Delta, where it appears to be taking hold.

Weed experts say that because the infestation was detected early, there is a good chance it can be eradicated or controlled relatively easily. But money to do that is tied up. By law, state agencies can spend money only to attack a handful of specified water weeds, including water hyacinth, Brazilian water weed and hydrilla.

State officials are sensitive to the possibility that lawmakers might yank on their purse-strings if they divert funds intended for one problem to attack another, especially in tight budget times, said Duane Schnabel, who heads the state food and agriculture department's integrated pest control branch.

That has prevented the state Department of Food and Agriculture from more aggressively looking for and removing spongeplant, even though the rule of thumb is that every dollar spent on the problem in the early stages of infestation might save $100 worth of work that could be needed later, he said.

Such an attack on spongeplants now could "avoid that catastrophic infestation" like water hyacinth, Schnabel said.

Democratic Assemblywoman Joan Buchanan is looking into introducing legislation next year to help them, according to her chief of staff Susanna Schlendorf.

"We are doing some investigation on it because there's growing evidence that it's spreading more quickly than some of these other species," Schlendorf said.

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