Reduction of powdery mildew caused by Podosphaera xanthii on greenhouse cucumber plants by foliar sprays of various biological and chemical agents.

摘要

Powdery mildew on cucumber plants caused by Podosphaera xanthii is a serious foliar disease for greenhouse growers worldwide. The disease is difficult to control under greenhouse conditions. Five experiments were conducted to determine the efficacy of a single post-infection foliar spray of two chemicals or seven biological treatments against powdery mildew on cucumber under near-commercial greenhouse conditions. Calcium nitrate at 15 g l-1 (44 colonies), Quadra 137 at 10 g l-1 (65 colonies), or undiluted homogenised milk (71 colonies) applied as post-infection sprays significantly (P=0.05) reduced the number of powdery mildew (P. xanthii) colonies on cucumber leaves compared with the water control (125 colonies) in five, four, and four experiments, respectively. Treatments with PlantShieldReg. at 10 g l-1 (85 colonies), or OrganoSanReg. at 100 ml l-1 (91 colonies) also significantly (P=0.05) reduced the number of powdery mildew colonies compared with the control (125 colonies) in three out of five experiments. Yeast S33, applied at 1x1012 CFU, and PreStopReg. at 10 g l-1 reduced the number of powdery mildew colonies in only two out of five experiments. These results suggest that calcium nitrate, milk, 'Quadra 137', OrganoSanReg. and PlantShieldReg. have the potential to control powdery mildew caused by P. xanthii on cucumber plants under greenhouse conditions..