Fungicides are a valuable tool in the fight against fungal diseases, however, their extensive use has led to the development of fungicide-resistant strains of fungi. This means that the fungicides that once worked effectively against these fungi are now ineffective. This is becoming a large concern in the world of agriculture as some common fungicides that farmers have relied on for years are losing their effectiveness. In fact, diseases of the crops we all know and love like grapes, apples and strawberries are showing resistance. Powdery mildew of grape, apple scab and strawberry anthracnose diseases are known to be becoming resistant to FRAC 11 fungicides and can cause considerable crop losses for growers.

A project funded by the Ontario Agri-Food Research Initiative allowed us to combine fungicide resistance testing with the Spornado early alert system for crop disease, which detects disease before it can be scouted. Over two seasons we tested Spornado’s ability to detect Powdery mildew, Downy mildew and Anthracnose and the G143A mutation that causes FRAC 11 QoI resistance. This new test allows the Spornado to assist in the selection of fungicides that may be more effective if resistance is detected.

This project collected samples from five vineyards in the Niagara region, three apple orchards and three strawberry fields both from the Southwestern Ontario. Disposable sample cassettes from the Spornado air sampler were changed twice a week.  The cassettes were then couriered overnight to Sporometrics testing laboratory. Samples were first tested for presence of the disease, if positive, further tested for the presence of the resistance mutation.  The results are shown in the table below:

Year                       Samples               QoI Resistant     QoI Sensitive

2021                       67                           59                           8

2022                       191                         171                         20

This data shows QoI resistance is widespread in the some of the most common diseases of Grape, Apple and Strawberry in Southern Ontario. When fungicides no longer work as they should, farmers and growers lose yield and quality. Additionally, fungicide-resistant strains of fungi can spread to other farms and fields, making it even harder to control the diseases they cause.

Fungicide resistance is a complex issue, and there is no one-size-fits-all solution. However, there are steps that farmers and growers can take to slow the development of fungicide resistance, such as rotating the types of fungicides they use, using them at the proper rates and timing, using disease-resistant varieties and other IPM practice, and monitoring for the development of resistance.

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