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QoI resistant apple scab confirmed in Ontario


February 24, 2010
By Fruit & Vegetable

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NEWS HIGHLIGHT

QoI resistant apple scab confirmed in Ontario
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.

Feb. 24, 2010, Guelph, Ont. – 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.

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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 and Sovran® from BASF.

“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.”


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