The winter phase of the milfoil control program on Osoyoos Lake in British Columbia, Canada, got underway last week as water temperatures continued to cool.
Unlike during the summer, when a machine cuts and harvests the tops of the invasive weed, between October and April a rototiller is used to pull the plant up by its roots.
There are two main reasons why the roots are only pulled up during the winter season and not in the summer, explained James Littley, office and projects manager with the Okanagan Basin Water Board.
One is environmental. Because pulling up milfoil roots actually disturbs the lake bottom, there are only certain times of the year when it can be done. In some areas, it is not permitted at all.
The second reason is that the plant is only dormant in cooler water temperatures. When it’s cold, the roots float ashore and die.