The invasive aquatic weed Eurasian Watermilfoil has decided to make an early appearance in valley lakes.

The invasive aquatic weed Eurasian Watermilfoil has decided to make an early appearance in valley lakes.

Early start for milfoil in Okanagan causing trouble

The invasive aquatic weed Eurasian Watermilfoil is making an early appearance in the Okanagan this year.

  • Jun. 20, 2015 9:00 a.m.

Just as tourists start to flood into the Okanagan for the start of beach season, the invasive aquatic weed, Eurasian Watermilfoil has decided to make an early appearance in valley lakes.  As a result, calls to the Okanagan Basin Water Board (OBWB) have already started.

“Usually we are just starting to survey the lakes to see where the milfoil is growing under the water and where we need to start working,” says James Littley, Operations and Grants Manager for the OBWB. “But I received our first call last week about the weeds and then today I had a couple calls saying the weed had broken the surface of the lake and is starting to form mats. It is looking like a good year for milfoil, and that’s bad for the rest of us.”

In summer 1972, the provincial government partnered with the Water Board and started an intensive program to remove the newly introduced, invasive milfoil from Okanagan lakes.  Early efforts focused on harvesting the weed, using everything from floating barges to hand-scythes and pitch forks.  The early goal was eradication by any means necessary – trying chemicals, bottom-barriers, dredging, and hand-pulling.  The program was handed over to the Water Board in 1998 and more recent control efforts have included research into breeding special weevils to eat the weed.  Today, the Water Board employs three operators who spend 1000s of hours on the water every year to control the volume of the invader at our beaches, boat launches and marinas, at over 200 sites in the valley.

Some wave off milfoil as just a nuisance that tickles your toes when you swim, but milfoil is bad for just about everything in our lakes.  Economically, uncontrolled milfoil has negative effects on tourism, and studies have shown that thick milfoil mats can lower lakefront property values by as much as 19%, noted Littley.  Environmentally, milfoil robs oxygen from the water, increases water temperature, slows the flow at the mouths of rivers, and increases polluting nutrients in the water.  It has also been linked to fish kills and loss of biodiversity.  Just last year, a provincial study found the primary factor reducing the flow of Okanagan River out of Vaseaux Lake was milfoil growth.

“Just think about that,” added Littley.  “The Okanagan River there runs at about 10,000 L per second in the summer – enough to fill an Olympic swimming pool in around four minutes – and milfoil is slowing it down.”

Luckily, most milfoil in Okanagan lakes is controlled.  Wood, Kalamalka, Okanagan, Skaha and Osoyoos all receive regular milfoil treatment through the OBWB program.  In the winter, milfoil operators rototill (uproot) the weed while it’s dormant. The roots are then left to freeze and die.  In the summer, the weed is harvested (or mowed) 6 feet below the surface and collected, then trucked to local gardens and orchards for fertilizer.  The program takes into account fish and other species habitats, spawning seasons, sensitive plants, at-risk animals, and special events like triathlons. Today the OBWB’s work is guided by electronic maps and tracked with GPS.  Staff use non-toxic lubricants, and have up-to-date safety equipment and protocols.

“We’ve come a long way from pitch forks and scythes,” said Littley.  “Still, the program faces challenges, and in some ways, we’re victims of our own success. If we do a good job, no one thinks milfoil is a problem.  But, as recently as last summer our equipment was robbed and vandalized.  We compete on the water and at boat launches for space with other boaters, sometimes leading to abusive comments to our operators.  Increasing development along the waterfronts can make some of our equipment loading sites inaccessible, restricting operations and lessening efficiency.  And of course, we still deal with breakdowns, frozen lakes, sick days, and the sheer volume and area of milfoil growth that we try to control.

“This year, the combination of the early snow melt and the record warm temperatures seem to have created perfect conditions for the milfoil to grow early,” says Littley. “We spent extra time on the water over the winter trying to get ahead of the summer growing season, but we just can’t compete with the changing climate.”

As bad as the milfoil problem is, the real threat now is if Zebra and Quagga mussels get into the Okanagan.  The invasive mussels are voracious water filters, allowing light to penetrate much deeper and increasing the habitat for milfoil. We can prevent the spread of both species by remembering to clean, drain, and dry our boats and other water equipment.

As we continue our regular business with milfoil, we ask residents of the Okanagan to be aware of the problems this nuisance invasive species has caused.  Now in our 41st year, the program has cost a total of over $18 million. “This is a drop in the bucket of what the next invasive could cost,” said Littley.

For more on the OBWB’s Milfoil Control Program, visit Also  For more on invasive mussels and the risks to the Okanagan, visit



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