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Recent changes in fungicide use and the fungicide insensitivity of plant pathogens in Canada.

Gossen, B.D., Carisse, O., Kawchuk, L.M., Van der Heyden, H., and McDonald, M.R. (2014). "Recent changes in fungicide use and the fungicide insensitivity of plant pathogens in Canada.", Canadian Journal of Plant Pathology, 36(3), pp. 327-340. doi : 10.1080/07060661.2014.925506  Access to full text


This review examines how changing fungicide usage in Canada is increasing the risk of fungicide insensitivity in pathogen populations, using examples from field, vegetable and horticultural crops. The current generation of systemic fungicide is selective, effective, and has a reduced impact on the environment compared to older contact fungicides. However, many of these new fungicides also have an increased risk of fungicide insensitivity. On the Canadian prairies, a trend towards specialization of production within regions has resulted in limited cropping rotations, or even no rotation, in many fields, and yield targets are increasing. As a result, the frequency and extent of fungicide usage is increasing rapidly and insensitivity to certain fungicides has been identified in several crop pathogens. Case studies of fungicide insensitivity on Ascochyta rabiei on chickpea, Mycosphaerella pinodes on field pea, Fusarium sambucinum and Phytophthora infestans on potato, Pythium violae, P. sulcatum and other species on carrot, and Botrytis cinerea on grapes and berry crops are examined. Fungicide manufacturers have taken action to protect the efficacy of high-risk fungicides by formulating them with active compounds with a different mode of action. Also, producers have been advised to rotate fungicides with different modes of action to minimize the risk of insensitivity. Monitoring for fungicide insensitivity is central to early warning of an impending issue with insensitivity, for disease risk prediction, and for avoiding disease control failures. In addition, information on insensitivity at the population level could be used to develop and implement insensitivity management programs.

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