Managing carrot powdery mildew

Abstract

A new disease to Australia, carrot powdery mildew (Erysiphe heraclei) damages carrot leaves making mechanical harvesting difficult. Field and greenhouse trials indicated that powdery mildew can be managed, but not eliminated, by fungicide application. Amistar®, Amistar Top®, Folicur®, Cabrio®, Fontelis® and sulphur were able to control the disease. Disease, as measured by leaf area affected, was reduced by up to 33 % (fungicide treated) but increased by up to 36 % (no fungicide) when comparing pre and post treatment assessments. Cultivar trials have been useful in identifying more tolerant cultivars, ‘Stefano’ (24 %) consistently had less powdery mildew as measured by leaf area affected than ‘Ricardo’ (51 %). The information collected identifies a suitable integrated management approach for carrot powdery mildew based on cultivar selection, careful monitoring, and tactical fungicide sprays. Disease expression over the study period was variable on time of appearance and level of severity.