Screening of fungicides for the control of ergot (Claviceps purpurea)

Abstract

This project investigated the activity of a range of fungicides on the fungus Claviceps purpurea which causes ergot in cereals and grasses. In vitro testing showed certain triazole and morpholine fungicides to be superior in their activity against Claviceps purpurea to the benzimidazoles which, until now, have been the only materials to be used (albeit without a manufacturer's recommendation) for the control of ergot. However, bio-assay of ovules dissected from ears four days after fungicides application (at anthesis), failed to detect the presence of the fungicides. This suggests very limited take-up of the active ingredients into the vulnerable organs of the inflorescence.

Of the fungicides tested, the morpholine fenpropimorph and the triazole difenoconazole were particularly effective against isolates of C. purpurea from both wheat and barley. Propiconazole was very effective against the barley isolate but not against that from wheat.

No ergot developed, even in the untreated control plots, in the spring wheat field-trial from which the ears were taken for dissection. None of the fungicides applied significantly affected the yield of grain.

The work demonstrated that there are now more effective fungicides than the benzimidazoles for the control of ergot. It did not, however, offer the hope that they are sufficiently systemic to penetrate to ovaries not exposed by the gaping of the glumes. Moreover, the absence of ergots in the inoculated trial clearly demonstrated that the routine application of fungicides against the disease will not always be cost effective even in areas where the risk of infection would normally be considered to be high. If fungicides are to be used against the disease, it will be necessary to develop effective risk assessment and forecasting systems.