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In Western Canada, Late blight does not create the overwintering spore type and requires living tissues to survive to the following season. In recent years, it has been found that Alberta typically has two different strains of Phytophthora, which has resulted in certain hosts being more seriously affected (for example, tomato crops). This can affect the types of outbreaks that occur. Some strains are more aggressive on tomatoes, while others prefer potatoes. Each strain differs in its virulence on either potato or tomato host plants. The monitoring and testing, it has been found that a number of different strains of the Late blight pathogen occur in any given area in a given year. Therefore, sexual spores are not known to be produced in Alberta and overwintering is only possible on living host tissues. Multiple zoospores can form within a single sporangium and are able to swim in films of water on the plant and in the soil to infect plant parts.Īn overwintering, sexual spore type called an oospore can also be produced by the pathogen if both mating types of the pathogen are present in an area however, only one mating type presently occurs in Western Canada. Sporangia (singular = sporangium) are formed mainly on infected foliage and are dispersed by wind and water. The Late blight organism produces two main spore types, referred to as sporangia and zoospores. The pathogen is highly aggressive and can potentially infect all plant parts, causing rapid die back and death. Scientists place this fungus in a group called 'Oomycetes', which are water moulds. The fungal pathogen, Phytophthora infestans, is the cause of Late blight.

While some varieties of these crops are less susceptible than others, NONE is immune. These include eggplants, peppers, petunias and Solanaceous weeds, such as nightshade species and wild tomato. The primary hosts of Late blight are potatoes and tomatoes however, other related plants can also be affected. Residential (rural and urban) plantings of potatoes and tomatoes are also impacted and at risk. Other industries that may also be affected include fresh market garden vegetables (potatoes and tomatoes), greenhouse vegetables (tomatoes, peppers, eggplants), as well as the greenhouse ornamental and garden centre industries (ornamental plants and vegetable transplants). Alberta's potato industry consists of approximately 50,000 acres, with the majority of the crop being grown for processing or seed.

The commercial seed, processing and table potato industries are at risk from Late blight. Which agricultural industries in Alberta might be affected by Late blight outbreaks? The commercial potato industry has expended a great deal of effort and cost in applying protective fungicides and maintaining quality seed, with some losses occurring. Since 2010, there have been reports of Late blight in potatoes and tomatoes in various regions across Alberta, with many urban or residential plantings and market garden crops damaged or destroyed and commercial potato crops also impacted. Major outbreaks occur occasionally in Alberta (the last one was in 1993). Late blight is found in most potato and vegetable growing regions of Canada and North America. Each year, Late blight reduces the yields of potatoes and tomatoes in the field and can cause major losses in potato tubers in storage. Late blight was responsible, in large part, for the Irish Potato Famine in the 1840's, which resulted in the death and mass emigration of millions of people. What is the historic and current/potential impact of Late blight In general, in Alberta, Late blight occurs infrequently, but can have devastating impacts in the years when it reaches epidemic levels. Late blight is one of the most serious diseases of potatoes and tomatoes worldwide, resulting in significant yield and quality losses annually.