State uses bugs to fight invasive Delta weed

August 2, 2011 12:53:18 PM PDT
A South American insect has been released in the Sacramento-San Joaquin River Delta in hopes that it will feast on an invasive aquatic weed choking the waterway.

Water hyacinth, a South American plant first introduced to the United States more than 100 years ago, is preventing boat access and clogging irrigation water intake systems in the much of the state.

The state Department of Food and Agriculture released the water hyacinth plant hopper in parts of San Joaquin and Sacramento counties early last month.

In a statement, department Secretary Karen Ross called water hyacinth, which is sometimes used to decorate landscaping pools, "a serious problem not just for agriculture and our state's water supply, but for anyone who appreciates the natural beauty and recreational value of our waterways."

Before a biological control agent like the plant hopper can be released in a state, it must be cleared by both federal and state regulatory officials, who weigh the risks of releasing the non-native species into the area.

"Megamelus scutellaris," commonly known as the water hopper, was chosen to act as a control agent because it is from the same part of South America as the weed. State food and agriculture officials say their research indicates that it feeds only on water hyacinth, calling it "an ideal candidate for release as a biological control agent."

Water hyacinth does more than clog waterways. By growing in dense layers that can completely cover a waterway's surface, the plant chokes off the sunlight that other plants need to grow.

A 2010 environmental assessment [PDF] of the water hopper by the U.S. Department of Agriculture found that water hyacinth growing in small ponds has caused declining phytoplankton populations.

By killing plankton, water hyacinth decreases the oxygen levels of its habitat. One of the reasons the hyacinth is so problematic is that even a small amount of the plant can have serious effects on its environment.

The USDA study found reduced plankton and oxygen levels under even modest water hyacinth growth, ranging from 10 to 25 percent cover. Modest hyacinth coverage also has caused declines in fish productivity, the study found.

The hope is that by removing this non-native plant species, native fauna will be able to flourish.

Steve Lyle, spokesman for the state Food and Agriculture Department, says the department is moving forward with the water hopper on a trial basis and is considering releasing more of them in other parts of the delta.

"We'll be watching them closely over the next couple of months to see what happens," Lyle said. "We need to allow science to play out and see if the bug has an impact. Science doesn't happen on a clock."

Story courtesy of our media partners at California Watch (A Project of the Center for Investigative Reporting)

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