Chlorine, potash tested as possible mussel control methods

Alberta wants to be ready for a fight if zebra and quagga mussels invade the province’s water bodies.

The small, invasive species multiply rapidly and cling to boats, water infrastructure and almost anything else. They clog pipes and machinery and consume water-borne nutrients essential to fish, plants and other aquatic species.

The mussels’ size and habitat make them difficult to kill.

Andrea Kalischuk, director of Alberta Agriculture’s water quality branch, heads a team that is testing potash and chlorine as weapons against zebra mussels.

“Why chemical control? Well, the other options that they’re using in closed systems, pipeline systems, are not going to work in our irrigation districts,” Kalischuk told the Alberta Irrigation Projects Association water conference Nov. 24.

“The other thing is that … we have about 4,000 kilometres of pipelines. There’s also about 4,000 km of farmer-owned lines. If we take the chemical approach and apply it through something like a fertigation approach, it should protect those farmer main lines as well as the pipelines.”

No chemicals are registered in Canada for controlling zebra mussels. Some chemicals suitable for closed water systems are approved in the United States but are unlikely to be useful in Alberta.

A biopesticide called Zequanox is expensive and scarce, and copper sulfate algaecides are toxic and can accumulate with lethal effects on other species and the ecosystem.

Magnacide, which is used to control weeds in water systems, causes zebra mussels to “clam up,” escaping any effect.

As a result, Kalischuk’s team is focusing on potash and chlorine as the likeliest options.

Potash (potassium chloride) kills mussels at 50 to 100 parts per million if they are exposed for two days. It is safe to work with and friendly to fish, plants and crops, said Kalischuk.

A much lower concentration of chlorine can kill mussels, but they would have to be exposed for 21 days to achieve 95 percent kill. Chlorine is toxic to humans, fish and plants.

Kalischuk has calculated cost of treatment at $3.47 per acre in a pipeline that, for example, serviced 23 pivots and 5,000 acres.

The cost for chlorine in the same system would be 46 cents per acre.

However, the chemical cost for potash would be nine cents per acre if a pivot system could be shut down and held static for two days. More than one treatment might be needed in the growing season because the mussels multiply and attach quickly.

“Potash has been used successfully in both lakes and rivers. We are not aware of it being used in pipeline systems,” said Kalischuk.

It was used to kill invasive mussels in Lake Winnipeg, but in a small treatment area near docks.

“The issue is if the whole lake isn’t treated, then the mussels are still viable in others parts of the lake and will re-establish.”

Kalischuk said the province has started the registration process for potash as a mussel control product, supported by Agrium, one of three potential suppliers.

Her team has also submitted a funding request to do more research this summer, primarily in the Eastern Irrigation District, to test potash preparation methods and pipeline injection equipment.

Researchers will also monitor the impact of potash treatment on water, soil and crop health and analyze the costs.

The southern Alberta river system is home to native species of mussels, which would be at risk if measures have to be taken against invasive types.

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