Lance, join the crowd. I'm in SW Ontario a few miles north of you and willow is a real concern for me. It spreads by tap root and can spread around your pond. If a piece is broken off and floats across your pond it can reroot in that location. For me, I let it grow in specific locations and in the areas I didn't want it to grow I cleared up the area down to the waters edge and used landscape fabric and rip rap the shoreline in rock to help stop this willow from establishing itself. However, my lake is bigger so you may be able to spray and respray this willow over time to kill it. Many of the chemical guys can tell you the type to use to eradicate this fast spreading shrub/tree.

Rowly