Control of powdery mildew on glasshouse-grown roses and tomatoes in the Netherlands using anhydrous milk fat and soybean oil emulsions

Abstract

Powdery mildew (PM) is a very serious disease affecting glasshouse-grown roses and tomatoes in the Netherlands. Control is limited because of resistance to existing fungicides. Anhydrous milk fat (AMF) and soybean oil (SBO) emulsions were evaluated for control of PM in roses and tomatoes. Both AMF (14 g/litre) and SBO (14 g/litre) provided powdery mildew control on rose leaves and blooms that was significantly better (P<0.001) than that achieved using formulated dodemorph acetate (2.5 ml/litre), a systemic fungicide commonly used by Dutch rose growers. Powdery mildew control with SBO was as good as that provided by dodemorph acetate on tomato fruit and flowers, while AMF was slightly less effective. Combination of SBO (3.5 g/litre) and AMF (3.5 g/litre) mostly provided PM control rivalling that of SBO (14 g/litre). Spraying roses with whole milk (20% v/v) left white residues. No evidence of phytotoxicity with the use of natural product emulsions was found on floral and fruit tissues.