Controlling pondweed in Dillon Reservoir

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From the Summit Daily News (Dr. Joanne Stolen):

Pondweeds are the subject of my current peeve. These submerged water plants can be both good and bad. They provide food and hiding places for young fish but, when overly abundant, allow too many of them to escape the larger predatory fish. Worst of all, in shallow waters, they rot under the ice in winter and may completely use up the oxygen, causing most fish to suffocate. The species that seems to be overly abundant along the shores of Dillon Reservoir currently is curly leaf pondweed. The scientific name is “potamogeton crispus.”[…]

Habitat manipulation such as draw-downs and dredging can also be used to manage curly leaf pondweed. Fall drawdown can kill the plants, exposing them to freezing temperatures and drying out. Dredging can be used as a control by increasing the water depth. In deep water, the plants will not receive enough light to survive. There are some chemical controls. There are a small number of aquatic herbicides that can be used to control curly leaf pondweed. Formulations of diquat (Reward) and endothall (Aquathall K) can be used in small areas and will usually knock down curly leaf pondweed within two weeks. The time for treatment is in spring or early summer when natives are still dormant and temperatures are low enough. Fluridone usually has to be applied to an entire lake and requires 30 days to knock down curly leaf pondweed. I doubt whether chemical controls would be appropriate for a reservoir. In any case if you are out and about in your boat on the reservoir, grab a few handfuls. It pulls out easily.

More invasive species coverage here and here.

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