Management of White Rust (Caused by Albugo Occidentalis) Of Spinach and Its Impact on the NonTarget Invertebrate Community

Abstract

White rust, caused by the oomycete Albugo occidentalis, is a major foliar disease of spinach (Spinacia oleracea). Favorable environmental conditions are required for its initiation and development. A modified version of a weather-based spray advisory program was evaluated using chemicals with different modes of action. Entomopathogenic fungi may infect Myzus persicae, a major pest of spinach. The nontarget effects of chemicals used in the management of white rust on entomopathogenic fungi and on the invertebrate community were also investigated. Both acibenzolar-S-methyl initiated at the second true leaf stage and pyraclostrobin applied according to the advisory program and weekly, reduced disease incidence compared to untreated plots. Naiad sprayed weekly reduced the percentage of aphid infested leaves, however no entomopathogenic fungi were isolated. All three chemicals caused population increases in predatory mites and phytophageous thrips. Actigard and Naiad caused increases in oribatid mites and beetle larvae populations