An inaugural survey of cereal, oilseed and vegetable crop diseases in the Yukon Territory in 2020

ABSTRACT

Various kinds of field crops growing on two commercial farms in the Whitehorse area of the southern Yukon Territory were surveyed for diseases in summer 2020 by staff of the Agriculture Branch of the Government of Yukon. They included barley, wheat, canola, beets, broccoli, cabbage, carrots, potatoes and turnips. Fields were visited one or more times during July and August. The incidence and severity of diseases were visually assessed on a crop-by-crop basis and samples were collected for laboratory analysis of the pathogens present, if any. Both infectious and non-infectious diseases were present on most crops. The infectious diseases were caused by various species of plant pathogenic bacteria and fungi that were common on these crops growing in other areas of Canada. INTRODUCTION AND METHODS: The 2020 field crop disease survey is believed to be the first organized study of its kind on agricultural crops in the Territory. In his book, "An Annotated Index of Plant Diseases in Canada . . . ", I.L. Conners lists over 300 records of plant diseases on trees, shrubs, herbs and grasses in the Yukon that were published by individuals who were surveying forests and native vegetation mainly for federal government departments, universities and other agencies (Conners 1967). The objectives of the 2020 survey were (1) to determine the kinds and levels of diseases on selected Yukon crops, (2) to identify the major pathogen species attacking Yukon crops, and (3) to use the results to plan future surveillance activities aimed at helping producers to improve their current disease management programs. All of the fields included in the 2020 survey were situated on two commercial farms, which were designated as Farm #1 and #2, in the Whitehorse area in the southern Yukon (Fig. 1). The crops surveyed included cereals (barley and wheat), oilseeds (canola) and vegetables (beets, broccoli, cabbage, carrots, potatoes and turnips). Fields were visited one or more times in the mid- to late growing season (July/August) at a time when damage from diseases was most noticeable. Symptoms were visually assessed on a crop-by-crop basis by determining their incidence and severity. Incidence was represented by the percentage of plants, leaves, heads, kernels, etc., damaged in the target crop, while severity was estimated to be the proportion of the leaf, fruit, head, root/canopy area, etc., affected by a specific disease as follows Proportion of the canopy affected based on a 0-4 rating scale, where 0 = no disease symptoms, 1 = 1-10% of the crop canopy showing symptoms;2 = 11-25% showing symptoms, 3 = 26- 50% showing symptoms, and 4 = > 50% showing symptoms. Photographs of affected plants were taken and sent to plant pathologists across Western Canada for their opinions on causation. Where possible, representative samples of plants with disease symptoms were packaged and sent to the Alberta Plant Health Lab (APHL) in Edmonton, AB for diagnostic analyses. Background information, such as the general cultural practices and cropping history, was obtained from the producers wherever possible. GPS coordinates were obtained for each field to enable future mapping Cereals Individual fields of barley (11 ha) and wheat (30 ha) located at Farm #1 were surveyed. The barley was a two-row forage cultivar 'CDC Maverick', while the wheat was an unspecified cultivar of Canada Prairie Spring (CPS) Wheat. Plant samples were taken along a W-shaped transect for a total of five sampling points for the barley field (< 20 ha) and ten sampling points for the wheat field (> 20 ha). The first visit, which occurred on July 30, involved visual inspection and destructive sampling wherein plants were collected and removed from the field for a detailed disease assessment at a lab space in Whitehorse. There, the roots were rinsed off and the plants were examined for disease symptoms. The second visit to these fields, which occurred on August 27, only involved visual examination of the standing crop. Oilseeds A single 40 ha field of Polish canola (cv. 'Synergy') was examined o