Weevils could be the answer to Lake Scugog weed woes

Invasive Plant Council of BC: (Published an Ontario letter to editor below:

Durham News, March 30, 2009 (ONTARIO)

There is a workable, environmental answer to the problem of out-of-control growth of the lake weed called Eurasian milfoil. The solution is to buy and install sufficient numbers of a native predator, the Milfoil weevil, to reduce significantly the thick infestations of this lake weed that we all find so obnoxious.This is a bio-control that has been used elsewhere with great success, that actually gives native plants a chance and yet has no negative effect on other species including humans.These weevils have historically been present in Lake Scugog because they ate the native milfoil, which is present but never in big supply. However, when the Eurasian variety of milfoil was introduced into our lake in the late 1960s, it took many years for the tiny, sesame seed-sized weevils to propagate to sufficient numbers to destroy the huge milfoil weed-beds that were as much of a problem in the 1980s as they are now.However, as their food weed-beds disappeared, their numbers once again crashed to low levels, allowing the milfoil once again to proliferate -- starting basically in 2006.Because non-native Eurasian milfoil is not just a Lake Scugog problem, but a North American problem, a company has sprung up that supplies quantities of weevils for 'salting' in milfoil-dominated lakes to speed up the natural predator/prey cycle -- with great success.The Scugog Lake Stewards witnessed evidence of a lake transformation using additional weevils from this company and were excited to hear that the Ministry of the Environment and the Ministry of Natural Resources have agreed with their use. There appears to be no downside to introducing additional weevils other than organization of the venture, finding funds and public education.

Introduced in tight plots within the weed-beds, weevils produce three to four generations each summer and each female will lay over 400 eggs in her lifetime. It is not an instant solution, but within two to three years, we could be able to use the bay recreationaly once again.

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Population boom for Lake Scugog weevils

Weevils Make Dramatic Progress in an Ontario Lake

Southern Ontario’s Puslinch Lake had been waging a losing battle against Eurasian watermilfoil for a number of years before deciding to become Ontario’s first Milfoil Weevil project. Located in Cambridge, ON, approximately 30 minutes southwest of Toronto, Puslinch Lake is approximately 400 acres (163 Hectares) with maximum and average depths of approximately 18 and 4.5 feet, respectively (5.5m and 1.4m). Owing to the very shallow depth and rich organic sediments in the lake, topped-out milfoil covered more than 50% of the lake surface when the MiddFoil project began in 2006. This coupled with very high stem density made Puslinch one of the most difficult project lakes we’ve worked with to date.

Fifteen thousand weevils were stocked in three locations during 2006; 24,000 were stocked in three additional locations in 2007; and 12,000 were stocked in two locations in 2008. Although follow-up surveys revealed limited progress during the first two years of the project, dramatic changes were noted by mid-summer 2008. As the aerial photos below illustrate, large areas that were topped out and very difficult to get a boat through are now clear of milfoil.