Decline continues | Rose stem girdler is killing wild roses in Alberta and Saskatchewan
Wild Rose Country without wild roses is just country. And the Wildrose Party without wild roses is just a party.
Neither Alberta’s licence plates nor its political opposition party is likely to change the motto or name, but they will have to make do with fewer of the iconic wild roses in the province.
So will the various mammals, birds, insects and other species that depend on the prairie flower for food, forage and habitat.
The villain: the rose stem girdler. The wood-boring beetle is slowly killing wild roses in Alberta, as well as a large part of Saskatchewan.
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Entomologist David Larson of Maple Creek, Sask., has been observing the roses’ decline. As a retired biology professor who taught for many years at Newfoundland’s Memorial University, he knows his beetles.
“I’ve been talking about the rose decline in southern Saskatchewan for 10 years. It’s been one of my pet interests here. I haven’t generated much interest,” said Larson.
“I thought I should tell Albertans about it. They’re losing their logo.”
Larson has seen evidence of the girdler’s damage to prairie roses as far west as Lethbridge and as far east as Regina, south to the U.S. border and in Saskatchewan’s Great Sand Hills, but that’s as far as he has looked.
“I suspect the distribution of this dieback is much more extensive than that.”
Greg Pohl, forest biodiversity researcher with the Canadian Forest Service, said in an email that the rose stem girdler has been tracked in the exotic pest database.
It has been documented in Ontario, Quebec, New Brunswick and Nova Scotia. There has also been one unconfirmed report from the Cypress Hills area of Alberta.
“But I trust Dave Larson’s report. He knows his beetles,” said Pohl.
Larson has written two articles in Nature Saskatchewan’s Blue Jay magazine about the girdler and its effects on prairie roses.
“I think it’s something that we should be more concerned about than we have been,” he said last week.
“The big effect is, we’re losing our three-dimensional structure in the prairie and things like jackrabbits or sharp-tailed grouse that need a bit of shelter … I think we are losing valuable habitat.
“I think there is some fundamental change coming about in parts of our prairie and it has ramifications other than just pretty roses. I think the wildlife out there is going to be adversely affected, if it hasn’t already been affected.”
The rose stem girdler is native to Europe and was found in Canada in the 1920s. It has a taste for both the prickly rose (Rosa acicularis) of the open prairies and the wood’s rose (Rosa woodsii) common to more shaded areas, aspen bluffs and riparian areas.
The beetle kills the rose stems by laying eggs on the plants, from which hatch larva that burrow under the bark in a characteristic spiral pattern. Their activity cuts off the stem’s supply of water and nutrients.
Prairie roses are hardy and not easily killed. As older stems are killed by the beetle larva, new ones spring up.
“You just get a constant pruning of the larger stems every year and you’re going from big, thick, impenetrable patches of roses to rather sparse stands of small, slender stems, which have fewer spines on them too, so they’re less protected,” Larson said.
Smaller, finer stems allow more sunlight to penetrate, which encourages grasses. Grazing animals, notably cattle, are attracted by the grasses.
The cattle open up the rose thickets and the area becomes open grassland.
Larson said he has anecdotal evidence and personal observation of this development in the Great Sand Hills, where once impenetrable rose thickets are now open and grazed.
Larson thinks the reduction in roses is worth studying, although no work exists or is ongoing, as far he knows.
“It’s one of these things that snuck in under the radar. I’m sure if roses were as big as the American elms that went through a similar die back in Ontario and Quebec back in the ‘70s, we would all be concerned.
“But these things being less than knee high, their demise and die off has just slipped in under our observation.”
As it’s not native to North America, the rose stem girdler has no natural enemies, but it’s possible that parasites might find them worthy hosts.
Infestation can be determined by removing a strip of bark from the lower half of the cane to expose a spiral, larval tunnel. During the growing season, infected roses will turn red prematurely and may retain their leaves throughout the winter.
Wild rose facts
- The wild rose or prickly rose, Rosa acicularis, became Alberta’s official floral emblem in 1930.
- It is common across the North American plains and as far north as Alaska.
- Acicularis means “prickly.”
- The prairie rose, Rosa woodsii, also grows across the plains and in alpine habitats from southern Yukon to Utah.
- Bloom typically starts in late May and lasts until early August.
- It is classed as a deciduous shrub. Larger stems are covered in small prickles with the occasional thick thorn.
- Its fragrant blooms are attractive to bees and other insects.
- Rose hips, considered the fruit of the plant, are eaten by birds, rabbits, squirrels, deer, moose and coyotes. They remain on the plant throughout winter.
- The inner seeds of rose hips are not palatable and if eaten, their fine hairs can cause a condition known as “itchy bum.”
- Rose hips are high in vitamin C and can contain as much as an orange. They can be used to make syrup, jelly, jam and marmalade. Along with leaves and flowers, they can also be used in tea.
- North American native people used roses to treat bee stings, colds, blindness and diarrhea.
- Arrows can be made from rose wood.
