Powdery mildew (Leveillula taurica) on greenhouse and field peppers in Ontario – host range, cultivar response and disease management strategies

Abstract

Leveillula taurica was observed on field pepper at various sites in south-western Ontario in 2005–2007. The field isolates collected from these sites were similar to a greenhouse isolate based on morphological observations. Host range of greenhouse and field isolates was similar, with minor sporulation on potato, carrot and several weeds. The greenhouse pepper cultivar ‘Samanta’ was the most susceptible to L. taurica while ‘Triple 4’, ‘Duplo’ and ‘Bosanova’ were the least susceptible to infection. Best control of pepper powdery mildew in the greenhouse was obtained with applications of myclobutanil, triflumizole, pyraclostrobin + boscalid, quinoxyfen, strobilurin derivatives (azoxystrobin, trifloxystrobin, kresoxim-methyl), copper soap, JMS Stylet-Oil®, Valent-10118, acibenzolar-S-methyl and sulphur. Disease reduction was also obtained with applications of potassium bicarbonate, citrus oil + borax, Bacillus subtilis and a fermented milk byproduct + surfactant. K2HPO4 + surfactant was effective in reducing disease whereas CaCl2 + surfactant, fumed silica and Sporothrix flocculosa were not effective. In field plots, best disease control was achieved with applications of myclobutanil and the fermented milk byproduct + surfactant in 2006 whereas in 2007, citrus oil + borax and potassium bicarbonate were most effective. There were no significant differences in pepper yield among the treatments in field plots. In vitro survival studies showed that the fungus was able to survive in infected pepper leaves after exposure to temperatures of −10 °C for 2 months.