Sweet Potatoes & Dutch Elm

Another request for sweet potato information; and a new preventative vaccine for Dutch Elm Disease
by Art Drysdale
by Art Drysdale


Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at

January 10, 2010


Above, a typical elm-lined city street, that very closely resembles Memorial Avenue here in downtown Parksville, B.C.; along with a winter shot of a typical American elm (Ulmus americana) ice-covered that I took in Toronto in order to show the typical branching habit of the American elm. Below, the Dutch Trigr® applicator being used on an elm tree, and finally the one gallon container of the chemical alternative, known as Arbortect 20-S.

Just last week Julie Olson from nearby Gabriola Island wrote about sweet potatoes. As it happened just back on September 13th last year I responded to a question on this subject from Northwestern B.C., a much colder hardiness zone than Gabriola Island here. Here was Julie’s question: “I was looking around the internet to try and find some sweet potato slips to buy. I have never grown them but thought I would like to try. It was quite surprising to find that you are so close to where I live, Gabriola Island. I do hope you are still growing them yourself and can supply me with some plants when the time is right. I look forward to hearing from you. Spring is coming.”

Well Julie, I regret to tell you that not only do I not grow sweet potatoes, I grow hardly any vegetables (two potted tomato plants only, last year). However, if you read my response to Lila at Triple Creek Ranch on September 13th, you’ll see my reference to Gregg Wingate of Mapple Farm in Weldon, New Brunswick. He is a grower/supplier of certified organic (OCIA & NOP) seed and plant stock. His specialties include: short-season sweetpotatoes, distinctive tomatoes, Jerusalem and Chinese artichokes, French shallots, Horseradish, Egyptian onions, garden soybeans and more. He has a brochure available: a) by request via e-mail , please let him know, though, where you're based (in serving residents from outside Canada they need to pass on some added info); or b) via standard snail mail free within Canada with a self-addressed stamped envelope (S.A.S.E.)--please make it at least a 4 by 9 inch envelope with a 54 cent stamp. From outside Canada, send $1 U.S.; Canada Post won't accept U.S. stamps.

From that list mentioned above, you may find some additional lesser-known items you wish to try as well.

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If you are a homeowner with American Elms on your property, you will no doubt be interested in a piece of news that was added to the ICanGarden site just last week. Since it was not a large item and had little ballyhoo I thought I would tell you more about it here, as well as repeating the salient points from Janet Feddes-Calpas of the Edmonton-based organization STOPDED (Society to Prevent Dutch Elm Disease).

For years there have been ‘new’ treatments for Dutch Elm Disease (DED). I well remember touring a group of over two dozen professional parks people all across Canada in August 1975. During a stop in Sault Ste. Marie Ontario then parks superintendent Harold Brain took us to a major park where one of his staff was injecting mature elms with one of the then new chemical products. The touring parks people came from well over a dozen countries ranging from Europe, Australia, New Zealand, and South Africa. Most were fascinated with the demonstration.

The problem has been that there is the ongoing ‘push’ to use a lesser number of ‘chemicals’ rather than introduce new ones. Presently, a product known as Arbortect 20-S (manufactured by Syngenta) is available from Rainbow Scientific Advancements of Minneapolis. It actually protects elms for at least two years but is a chemical that requires mixing and pressure on site, and the chemical is considered toxic.

The news announced here last week involves a water-based biological treatment that is actually a vaccine that must be applied to each tree annually. Here is a summary of the new treatment.

“A bio-vaccine that is 99 per cent effective in the prevention of Dutch elm disease is now approved for use in Canada for the first time. Health Canada's Pest Management Regulatory Agency (PMRA) has completed an extensive review and approved full registration for the bio-vaccine Dutch Trigr® as of October 19, 2009. Dutch Trigr® is unique be-cause it is a biological solution that is chemical free. It is a pure suspension of conidiospores of Verticillium isolate WCS850 in distilled water. Once injected, the vaccine induces a response from the immune system of the tree and stimulates its natural defence mechanisms.

“‘It's like getting a flu shot for your elm,’ says Philip van Wassenaer, president and chief consulting arborist of Urban Forest Innovative Solutions, a Mississauga, Ontario company that is distributing the product. ‘With these defence mechanisms up and running, the elm is able to successfully defend itself from Dutch elm disease throughout the growing season. Canadians can now protect their elm trees from Dutch elm disease with an effective, low cost and completely safe biological treatment.’

“While significantly reduced by Dutch elm disease for the past 60 years, elm trees are still found in many of Canada's urban forests. Across the prairies, provincial and municipal governments spend millions of dollars annually to protect their precious elm populations.

“Dutch Trigr® was originally created at the University of Amsterdam. It has been used effectively in Europe since 1992 and the United States since 1995. Urban Forest Innovative Solutions is the only distributor of Dutch Trigr® in Canada. Dutch Trigr® is available for use by municipalities and tree care companies to protect both private and pub-licly owned elm trees.”

So there you have it--interesting news that could have a major effect on the few stately American Elms that remain in our Canadian landscapes. For more information check the Website: .

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