I noticed last autumn that the Scots pines (Pinus sylvestris) near my cottage were dying off. Any idea what could have been killing them?—Melanie Foord, via email
“It is definitely hard to say without seeing the trees,” says Steve Smith, an arborist with Bartlett Tree Experts in Calgary. “There are a few fungal diseases that can attack pines. The only one I know that seems to favour Scots pine is Lophodermium needle cast.” The needles develop yellow spots, then can turn brown and eventually fall off. Unfortunately, “the fungus is hard to identify on trees because the symptoms are similar to a lot of other tree problems,” says Smith. “We often need to send samples to our lab to confirm.”
Another possible contender is Diplodia pinea, a.k.a. Sphaeropsis sapinea, says Tracy Logan of Logan Tree Experts in Lakefield, Ont. It causes tip blight: you’d see short, stunted brown needles with black specks at their bases. “All two- and three-needle pines are hosts to this disease.”
If a fungus was the culprit, it probably wasn’t entirely to blame. “The first thing I always go towards is environmental conditions,” says Matt Logan, also with Logan Tree Experts. “Too much water; not enough water; too much wind; too cold; poor soil composition…most tree stress is cumulative.” A strong tree may be able to survive an infestation. But not a tree that’s been weakened by multiple environmental factors.
It’s also possible that what you saw was normal seasonal needle drop, says Smith. “The needles on pine trees only last so long, and as the new growth begins to shade out the interior, the tree sheds some of the unproductive needles.” It can be more pronounced in years where the trees have experienced more stress, such as long periods of drought, which we had last year, says Smith.
Don’t cry too hard for these possibly fungus-filled and stressed-out Scots pines. This tree isn’t native to Canada. The Ontario government introduced it in the early 1900s to help deal with soil erosion problems after consulting with European forestry experts. (Because…Canada had no forestry experts in 1925? Seems weird, but okay, government.) As is so often the case with an introduced species, after doing its intended job, Scots pine went rogue, outcompeting native trees and disrupting sensitive ecosystems.
Are we sad when trees die? Goodness, yes. Are we sad when this tree dies? Meh.
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This article was originally published in the September/October 2022 issue of Cottage Life.