Zombie plant a threat to fish and even swimmers

·1 min read
The zombie plant forms thick mats that even fish have trouble getting through, and can entangle human swimmers. (Organisme des bassins versants de la Haute-Côte-Nord - image credit)
The zombie plant forms thick mats that even fish have trouble getting through, and can entangle human swimmers. (Organisme des bassins versants de la Haute-Côte-Nord - image credit)

Prince Edward Islanders are being asked to take extra care when moving their boats around this fall.

The Nature Conservancy of Canada is concerned about the spread of Eurasian water milfoil, also known as zombie plant. The invasive species has been reported at a few sites on P.E.I.

"It's a challenging one to manage," said Andrew Holland, national media relations director with NCC.

"It takes up a lot of space. It grows in ditches and marshes, streams, lakes, shorelines and it spreads quite rapidly, and it replaces and outcompetes native plants."

It's like a hitchhiker. It hitches a ride on your boat or your trailer. — Andrew Holland

Milfoil can establish itself in water as deep as 10 metres, and forms thick mats that grow up to the surface, blocking out light for other vegetation. It can become so thick that even fish have trouble getting through it, and it can be a hazard for swimmers who might get caught up in it.

It also creates pools of stagnant water that are ideal for mosquitoes.

Spread by people

Milfoil can spread from one body of water to another by fragments that get stuck to boats or boat trailers.

"It's like a hitchhiker. It hitches a ride on your boat or your trailer," said Holland.

It can be very difficult to control the zombie plant once it is established.

In the Saint John River divers pull it up by hand, while in B.C. an underwater rototiller tears up the plant, and in Ontario herbicides are used.

The best way to control it, he said, is to keep it from establishing in the first place.

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