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June 6, 2012

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Fight against floating pest started early

SHANGHAI may have more problems this year with azolla, a free-floating aquatic fern, the city's waterway sanitation authorities said yesterday.

The plant is a long-time headache for the city during summers.

Officials said they started early this year to remove the water plant since more rainfall than last year is expected this summer, the drought last year partly held off the growth of the fern, officials said.

"They came earlier compared with last year, so we responded earlier," said Guo Hua, an engineer with city sanitation.

Workers began the cleanup on May 5, about a month earlier than last year. The fern, which comes from upstream, spreads into the city's Huangpu River and Suzhou Creek and smaller tributaries.

The plum rain season may arrive early, forecasters say, making cleanup more difficult since that's when the plants grow faster and water channels are more easily clogged.

More than 11,800 tons of azolla have been removed citywide so far, officials said. Vessels used to remove azolla are to be added. The plants can reproduce quickly and cover a large area in a short time.

Most of the floating plants need to be stopped upstream in suburban areas such as Songjiang and Minhang District.

Guo said the city has been fighting the fern, as well as water hyacinth, another nuisance water plant, for more than 10 years.

Besides being unsightly, the plant can cause problems for vessels.

Because of its nitrogen-fixing abilities, local azolla is used as a fertilizer. Sometimes villagers also use it to feed livestock.


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