Cereal stem-base disease - a complex issue

PCR assays were used to evaluate the accuracy of visual assessment of stem-base diseases of winter wheat and identify the predominant stem-base pathogen species present in the UK. At early growth stages, pathogenic fungi were identified in the absence of symptoms. At later growth stages, there was generally good agreement between occurrence of symptoms and causal pathogens identified by PCR. Quantitative PCR was evaluated as a means of determining the efficacy of fungicides and cultivars against stem-base pathogens and for risk assessment. Cyprodinil controlled both eyespot pathogens, Tapesia acuformis and T. yallundae, but prochloraz gave consistent control only of T. yallundae. Despite significant control of eyespot, yield increases were moderate and were only achieved on the most susceptible cultivars. Azoxystrobin increased yields most consistently but there was no evidence that this occurred through control of stem-base diseases. It was active against sharp eyespot, which was present only at low levels. Brown fool rot was associated only with Microdochium nivale, which was affected little by fungicides.