QoI resistant apple scab confirmed in Ontario orchards
February 16, 2010
A recent sampling program of scab-infected apple leaves from orchards across Ontario has revealed the presence of QoI-resistant apple scab. QoI (quinone outside inhibitors) is a group of fungicides that include strobilurins.
During the 2009 season, Bayer CropScience coordinated the collection of samples from nine apple orchards in Ontario. The samples were taken from Ontario orchards located in almost all major apple growing regions. Testing completed at Michigan State University confirmed that apple scab tissue from seven of nine locations was resistant to QoI fungicides.
This is the first recorded resistance in Canada to QoI fungicides, a group that includes Flint® from Bayer CropScience.
“As a result of this study, Bayer CropScience is advising apple growers in Ontario not to use Flint for control of apple scab during the 2010 growing season,” says David Kikkert, Portfolio Manager, Horticulture for Bayer CropScience. “Flint continues to be a great option for control of powdery mildew, fly speck, sooty blotch and cedar apple rust. In addition, Bayer CropScience is advising apple growers outside of Ontario, to tank mix Flint with a compatible registered contact fungicide (EBDC) to provide two modes of action working to control apple scab.”
Each of the nine samples consisted of up to 50 leaves (one leaf per tree) taken randomly from apple trees on an orchard. From these 50 leaves, one single-spore fungal isolate per leaf was selected. And from these, a maximum of 25 individual fungal isolates per orchard were tested to determine if isolates were susceptible or resistant to QoI fungicides for control of apple scab.
“The presence of QoI resistant apple scab is a concern for apple growers,” says Andrew Dornan, Senior Field Development Representative, Horticulture with Bayer CropScience. “Based on the results of this first study, and in the ongoing interest of sustainable pest management practices, Bayer CropScience will continue sampling and testing apple orchards in 2010.”
Information on apple scab
2009 was the worst scab year on record in Ontario. Apple scab is the most serious fungal disease of apple in Canada and is a significant economic threat in all apple-growing regions. Apple scab disease and infection is favoured by cold winters and wet growing conditions, and is of major economic importance in Eastern Canada. It occurs every year and often causes significant economic losses. Losses result directly from fruit infections which affect yield, fruit quality and storability or indirectly from defoliation which can affect tree vigour and winter survival. Left uncontrolled, apple scab can result in 100% crop loss in any given year. Losses are typically less serious in British Columbia, where the weather is usually dryer, although they can be significant in certain fruit growing areas of the interior of the province.
From the Pesticide Risk Reduction Program, Pest Management Centre, AAFC, November, 2009
About Bayer CropScience
Bayer is a global enterprise with core competencies in the fields of health care, nutrition and high-tech materials. Bayer CropScience AG, a subsidiary of Bayer AG with annual sales of about EUR 6.4 billion (2008), is one of the world’s leading innovative crop science companies in the areas of crop protection, non-agricultural pest control, seeds and plant biotechnology. The company offers an outstanding range of products and extensive service backup for modern, sustainable agriculture and for non-agricultural applications. Bayer CropScience has a global workforce of about 18,000 and is represented in more than 120 countries.
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