MEDICINE HAT, Alta. – A number of planets need to align for new plant diseases to make their way onto the Prairies: a susceptible plant; an aggressive or virulent pathogen and favourable environmental conditions.
Ron Howard, a plant pathologist with Alberta Agriculture, recently told a Reduced Tillage conference in Medicine Hat that this can occur either through natural spread or through artificial introductions, such as diseased seed and infested machinery.
“The single most important factor influencing disease development in field crops is the weather. That has a profound effect, not only creating favourable conditions for the pathogens to grow and reproduce, but whether or not the crops are stressed in the process,” Howard said.
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“There’s two categories of diseases: those we term as infectious or biotic diseases caused by bacteria, fungi, viruses and other pathogens or parasites. Then there’s the abiotic diseases or noninfectious diseases due to environmental stresses, like excess or deficiencies of moisture, nutrients, low or high temperatures. With a flooded crop, it’s more prone to root rot caused by soil borne fungi.”
Howard said climate warming may increase the incidence, severity and variety of warm weather diseases that are able to infect prairie crops.
“Some of the diseases we may never see here,” he said.
“Some are pretty nasty, but there’s indications that with some of the changing weather patterns, we’re seeing diseases we haven’t seen before and that’s causing us some concern.”
Western Canadian researchers are conducting a number of crop disease surveillance projects, such as local and regional crop surveys that occur every year.
As well, Alberta has the Alberta Pest Monitoring Network, a consortium of university, provincial and federal scientists that target new and existing diseases, insects and weeds.
The network selects a few each year for in-depth surveys.
Howard describes internal threats as diseases that are already known to occur on the Prairies and that could spread into new areas or develop new strains that could increase their impact and economic importance.
“They’re out there now, maybe in localized areas in low levels, but given the right conditions they could really take off.”
External threats are diseases not known to be established on the Prairies, which if introduced could gain a hold and significantly impact not only crop yield and quality but also the biodiversity of native plants.
“These are things we don’t want to see introduced. Sometimes customers will raise questions (about disease incidence) whether they want to import our commodities,” Howard said.
“An example is with alfalfa seed. The Chinese are concerned about a disease called bacterial wilt. There were reports years ago of this disease on the Prairies. Before they would import Canadian alfalfa seed they wanted to makes sure there had been no reports of that disease within the past 10 years.”
