Effectiveness of antifungal compounds against rose powdery mildew (Sphaerotheca pannosa var. rosae) in glasshouses

The efficacy of several antifungal compounds, chosen among salts, oils, plant extracts, and of the hyperparasitic fungus Ampelomyces quisqualis , were tested in seven glasshouse trials against powdery mildew on roses ( Sphaerotheca pannosa var. rosae ) in Sanremo (N. Italy). In the presence of a high disease incidence (55% of untreated leaves infected in six out of seven trials), all the antifungal compounds and the biocontrol agent A. quisqualis , applied individually, provided satisfactory control of powdery mildew. Most treatments were as efficient as the fungicide dodemorph, which, sprayed at weekly intervals, provided a 75% average efficacy throughout the trials. Among the test compounds, KH 2 PO 2 , at 0.5 and 1%, offered good and consistent disease control, NaHCO 3 , at 0.5%, showed a satisfactory level of activity, while at 1% it was phytotoxic. Wine vinegar, applied at 5 and 10%, gave good control, but acetic acid was phytotoxic. JMS Stylet oil, the canola oil, Synertrol and neem extract provided satisfactory disease control. Fatty acids formulated as potassium salts significantly and consistently reduced powdery mildew severity, but caused some phytotoxicity. Milsana, a concentrated extract from leaves of Reynoutria sachalinensis , only partially controlled powdery mildew. Several strategies based on the rotation of different antifungal compounds, with or without the application of dodemorph, provided very good, consistent disease control. The potential of some of the antifungal compounds and of the biocontrol fungus A. quisqualis against rose powdery mildew is discussed.