Over the last several years, a plant-killing pathogen has crept into a handful of Nova Scotia Christmas tree farms.
Phytophthora, otherwise known as root rot, is a species of microorganism that can affect plants ranging from oak trees to rose bushes. It was even one of the major causes behind the 19th century Irish potato famine. The microorganism is most closely related to brown algae, but exists on land, thriving in damp conditions. The microorganism’s spores move through the soil infecting plants’ roots, leading to discolouration, stem cankers, and eventually, death.
“We never faced phytophthora until the last few years,” says Matthew Wright, a Nova Scotia director of the Canadian Christmas Tree Association. “It’s come from the introduction of imported seedlings, people trying to see if they could grow the Fraser fir, which is very popular in many markets. In importing it, they didn’t realize that they were importing phytophthora until it started to kill seedlings.”
There are several types of phytophthora, but the pathogen affecting Nova Scotia Christmas trees is phytophthora abietivora. In North America, experts first identified this species of root rot in diseased Christmas trees in Connecticut in 2010. It then spread to natural environments in both Pennsylvania and Virginia. The pathogen has since made its way to Canada, identified in forest nurseries and Christmas tree plantations in Quebec, and some forested areas in Ontario.
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In Nova Scotia, Wright says the root rot has yet to jump to the natural environment. It’s remained isolated in Christmas tree fields, which only make up a small percentage of Christmas tree growers’ sites. “A good solid 98 per cent or more of our production is from natural stands,” he says. “Planting into natural stands is a little bit different than planting into fields.”
Natural stands are forested areas where balsam firs, native to the area, grow naturally. Christmas tree growers clear out the hardwood to give the balsam firs more space to grow. They harvest a certain number of trees each year, allowing natural seed sources to regenerate the population.
So far, Wright hasn’t seen any root rot in the natural stands. “There does seem to be a more natural resistance to phytophthora in the balsam than the Fraser species,” he says.
Nova Scotia growers are monitoring their trees closely for any signs of root rot, trying to catch it early. Wright says there’s been some research out of Quebec and Oregon that suggests planting saplings on raised mounds, especially in wet conditions, gives them a better chance against root rot.
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Global warming is also playing a factor, allowing root rot to survive for longer. “We didn’t deal with phytophthora for a long time because in the north, our frosts would go eight to 18 inches deep, meaning that we would often freeze out the life stages of the disease,” says Wright. “But all of a sudden, we’re not getting those kind of deep frosts anymore. So, we are seeing the spread of phytophthora northwards.”
Despite this, Wright is confident that the root rot shouldn’t impact the availability of Nova Scotia Christmas trees this year. It’s an industry that by his estimate contributes between $20 to $30 million annually to the economy. In fact, it could make the industry stronger.
“As we learn to manage it, we may spend a little bit more money to prepare the fields, but when your survival rate is approaching 95 per cent instead of 40 or 50 per cent, your return just comes in the trees that you have available to sell,” he says. “So, in fact, doing this upfront work to avoid phytophthora may actually improve the bottom line for our Christmas tree growers.”
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