Many trees in Nova Scotia aren’t waiting for fall to start dropping their leaves. One of the reasons behind it is a fungal blight referred to as tar spot. The fungal infection is widely affecting the Norway maple tree. James Steenberg, assistant professor at Saint Mary’s University in Halifax, says it’s one of the most planted tree species in North American cities. “They’re definitely the most common in Halifax,” he says. “Every several years when the conditions are right – usually wet springs and things like this – a collection of species of fungi cause this tar spot.” He says the effects are quite noticeable. “You’ll see an early leaf drop, early senescence, but it’s more of a cosmetic issue, it’s not going to kill these trees,” Steenberg explains. “Because so many of our street trees are this species, we do see it everywhere.” Residents can pick up the foliage once it’s on the ground before snowfall, removing habitat but also reducing the likelihood of more tar spot returning the next year. Steenberg says a big question he and researchers are tackling is how climate change impacts the issue. “We’re seeing more erratic weather conditions, warmer temperatures but also more sporadic, less predictable events like droughts like we saw last year, which we’re probably still experiencing the impacts from,” says Steenberg. He adds climate change brings conditions that stress the forests, but also a more tolerant environment for introduced invasive species. “And we have a lot of those in Nova Scotia and in Atlantic Canada, for sure,” he says. Many communities have been hit by the Japanese beetle, emerald ash borer, and hemlock woolly adelgid. “These introduced invasive insects essentially cause 95 to 99 per cent mortality of these tree species that are so important ecologically and to people in their community,” says Steenberg. Aside from insects, he notes there’s also a resurgence of Dutch elm disease, another fungal infection that emerged half a century ago. “But I’m seeing Halifax’s elm trees now that were largely spared from Dutch elm be affected by this condition again,” he says. Steenberg advises people involved in tree planting to build in diversity. “That helps build ecosystem resilience, so the more species and more different structures you have, the less likely you are to be impacted by one given impact,” he says. For more Nova Scotia news, visit our dedicated provincial page
