Maximising the effective life of fungicides for the control of foliar diseases in oilseed rape

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Maximising the effective life of fungicides for the control of foliar diseases in oilseed rape

Economic losses attributable to light leaf spot (Pyrenopeziza brassica) and phoma leaf spot/stem canker (Leptosphaeria maculans/Leptosphaeria biglobosa) were estimated to be over £220 million nationally in 2014, with light leaf spot overtaking stem canker as the major disease affecting oilseed rape in England and Wales. Control depends on a combination of chemical and non-chemical practices, with a significant contribution from foliar fungicides; predominately a single chemical group, the triazole. Two mutations (G460S and S508T) conferring insensitivity to triazole have been identified recently in isolates taken from the UK P. brassicas population, both affecting the binding of azoles at the CYP51 target site. The positions of these mutations are similar to those conferring triazole resistance in other plant pathogens including Zymoseptoria tritici in cereals. There is currently no evidence available to the industry to demonstrate the effect of current treatment regimes on selection for such fungicide resistant strains. There is a strong rationale that the current widespread use of solo active substances in spray programmes represents a very poor anti-resistance strategy. This project will aim to address this gap in knowledge by evaluating alternative fungicide resistance management strategies which will be cost effective to growers and maximise the effective life of fungicides to protect oilseed rape yields long term. This AHBD-funded project will address two objectives: Objective 1. Determine the risk of fungicide resistance occurrence for oilseed rape fungicides against the key diseases affecting oilseed rape in the UK; Objective 2. Test selection for fungicide insensitivity mutations in UK the P. brassica population through application of solo products or mixtures.

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