Control of powdery mildew (Sphaerotheca pannosa var. rosae) on rose (Rosa L. sp.) using anhydrous milk fat and soybean oil emulsions

Abstract

Powdery mildew (PM) is a serious fungal disease of a wide range of horticultural crops and can adversely affect crop yield and quality. Anhydrous milk fat (AMF) and soybean oil (SBO) emulsions were evaluated for control of PM (Sphaerotheca pannosa var. rosae) on potted rose plants (Rosa L. sp. 'Splendid Surprise' and 'Sahara') maintained in a controlled environment. Foliage was sprayed weekly with AMF (0.7% w/v), SBO (2% w/v), fungicide (Supershield™, 1% v/v), water, or left unsprayed. PM infection increased to 100% leaf area in water and unsprayed control plants over 6 weeks. The fungicide reduced infection to a severity rating of 5 (>40% leaf area infection). The AMF and SBO treatments gave significantly better disease control (P <0.0001) with a severity rating of 2 (2-5% infection). Some yellowing and necrosis of leaves was observed on plants in the SBO treatment, but overall leaf health was superior to that of control plants.