Canadian conservation authorities on Tuesday celebrated a succesful test using liquid fertilizer to kill invasive Zebra mussels in a lakefront harbor in the western province of Manitoba.

"The treatment process came to a successful end at Winnipeg Beach Harbour on Monday with all... mussels pulled from the harbor confirmed dead after day nine of the estimated 10 day treatment process," Manitoba conservation authorities said a statement.

The fight against the mussels will now move to three other nearby harbors, they added.

The small freshwater mussels are native to Eastern Europe and Western Asia. They were discovered in the four Lake Winnipeg harbors last year.

"We need to take immediate action to combat the threat of a zebra mussel infestation in Lake Winnipeg... before they spread further and cause permanent damage to the ecosystem or to Manitoba waterways," Conservation Minister Gord Mackintosh said at the time.

Conservation officers killed them off by applying liquid potash to waters for 10 days and closing off the harbor with a gated silt curtain to keep the potash in.

Liquid potash is a plant nutrient mined in vast quantities in neighboring Saskatchewan province and sold to farmers worldwide.

Dumping it in a lake does not impact fish, nor water quality, its concentration eventually dissipating.

Zebra mussels (Dreissena polymorpha) reproduce at an alarming rate, damaging harbors and waterways, ships, water treatment plants and power plants, as well as disrupting the aquatic food chain.

They were first detected in North America in 1988 in the Great Lakes, after catching a ride in the ballasts of transport ships, before spreading across the continent.

Millions of dollars are spent annually to fight the scourge, with mixed results.