WINNIPEG -- Manitoba plans to start sealing off four lake harbours after the long weekend in a bid to quash an invasion of zebra mussels.

The province has announced it will close off the harbours with a curtain before pumping them full of liquid potash.

It's believed to be the first time the method has been tried in open water and scientists are calling it a "golden opportunity" to kill the zebra mussels before they take hold.

The province says the curtain will be opened to allow commercial fishing boats in and out of the harbours.

The treatment is expected to be completed by early June.

Zebra mussels are an invasive species that can disrupt the food chain, clog water pipes and create algae.