Milfoil infestation continues to plague Okanagan watershed

Maintenance program effective but still absence of eradication solution

Harvesting Eurasian milfoil in Okanagan Lake. (File photo)

It has been more than 50 years since the invasive Eurasian milfoil emerged in the Okanagan Water Basin.

The weed growth has no maintenance cure, as the plants were introduced and have since spread throughout the Okanagan Valley watershed from Osoyoos to the north end of Okanagan Lake.

Some 4,100 metric tonnes of milfoil have been harvested since 1981, as the Okanagan Basin Water Board continues to fund a milfoil control program which entails derooting or rototilling in the winter and harvesting in the summer at a cost of $780,000 annually.

“The healthy, clean water we see through much of the valley now is partly due to the removal of milfoil,” says the milfoil control aspect of the OBWB’s annual report released at the organization’s annual general meeting in Kelowna earlier this month.

“Most visitors, residents, and even decision-makers are unaware of the past harms caused by widespread and uncontrolled milfoil in the Okanagan, as well as its continued harmful ecological and economic effects.”

James Littley, OBWB operations and grants manager, spoke about the milfoil control program at the annual general meeting, talking about the history behind it and how research efforts, some led by UBC Okanagan, on maintenance techniques.

Littley said removing the milfoil is arduous and never-ending work at this point, but remains the most cost-effective and neutralizing control option.

Chemical treatments have not worked, with one effort in the ’70s to use the controversial herbicide 2,4-D leading to public protests banning its use.

“Ultrasonic treatment methods held some promise for a time…technology offers some hope for new methods to be developed but so far there has been no dedicated solution,” Littley said.

Milfoil’s characteristics of impacting water quality and negatively impacting the ecosystem are a foreshadowing of why the threat of invasive mussels is a high priority for the water board, another invasive element to the watershed with no treatment solution that could pose an economic disaster for the region.

“The challenge with chemical eradication of milfoil or the mussels is the sheer size of Okanagan Lake. There is no way it can work like it might on smaller lakes or reservoirs,” Littley said.

While the milfoil harvesting has been effective, Littley said the federal government declaring a particular mussel native to Okanagan Lake as an endangered species has curtailed milfoil harvesting in those areas, allowing the weed to proliferate.

Looking forward, infra-red camera initiatives have provided a more detailed way to monitor and decipher milfoil growth from other aquatic plant life native to the lake.

The UBCO School of Engineering has also designed a new way to reduce the volume of harvested weeds to store them on a barge or boat without requiring nearby transfer sites on shore.

As well, the harvested milfoil has found a recycling purpose for use by local farmers.

“Our reality is we have to learn how to live with the milfoil problem. Our taxpayers are on the hook for this without provincial government funding support which ended in the 1990s, chemicals are not a solution and research holds out hope to control the ecosystem balance,” Littley said.

READ MORE: Milfoil control cuts hurt Okanagan lakes

READ MORE: Swimmer gets entangled in milfoil

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