Control of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape (Brassica napus) with resistance elicitors

Abstract Field trials were conducted over two years (2008/2009 and 2009/2010) to examine the effect of a combination of resistance elicitors on light leaf spot ( Pyrenopeziza brassicae ) on oilseed rape ( Brassica napus ). The elicitor combination comprised acibenzolar-S-methyl (ASM), β-aminobutyric acid (BABA) and cis- jasmone (CJ), and its effects were compared to those of the following fungicide treatments: [1] prothioconazole (used in 2009), and [2] prothioconazole/tebuconazole, and metconazole (used in 2010). In both years, the elicitor combination applied on its own, provided significant control of light leaf spot. In 2009, the elicitor combination was more effective than the fungicide in reducing light leaf spot severity at GS1.9, while levels of disease control at GS3.1 and 4.5 were similar for both elicitor and fungicide treatments. In 2010, the elicitor combination was less effective than the fungicide programmes in reducing light leaf spot severity at GS1.9, but produced similar levels of disease control at GS3.1 and was more effective than the fungicide at GS4.5. Probably because of the relatively low light leaf spot severity observed in the 2009 and 2010 field experiments, none of the treatments produced a significant effect on yield. Based on these data, and in view of the poor performance of fungicides in regions at high risk from light leaf spot, resistance elicitors might offer the potential for a new approach to controlling light leaf spot on oilseed rape.