Efficacy of locally available fungicides in controlling powdery mildew of Butternut squash (Cucurbita moschata Duchesne ex Poiret) in greenhouse at Sebele, Botswana

Abstract

The powdery mildew of butternut squash (Cucurbita moschata Duchesne ex Poiret) caused by Podosphaera xanthii (Castagne) U. Braun and Shiskoff is the most severe disease in Botswana. The disease causes a significant reduction in quality and quantity of butternut fruits. Greenhouse experiments were conducted during 2007 and 2008 at the Department of Agricultural Research Station, Sebele, Botswana to evaluate the efficacy of locally available protectant and systemic fungicides on the control of the powdery mildew of butternut squash. In 2007 treatment trial included a protectant fungicide, chlorothalonil and two systemic fungicides, benomyl and bupirimate which were used separately, and tank mixes of each of the systemic fungicide with the protectant fungicide. Fungicidal treatment in 2008 included an additional protectant fungicide, mancozeb which was used alone and also tank mixed with systemic fungicides used in 2007. Chlorothalonil and mancozeb when used alone were not effective in controlling the disease with the disease severity (DS) of 23.52% and 9.43% respectively over 31.45 % disease severity in non-treated plants. Out of the two systemic fungicides, bupirimate (1.21% DS) was more effective over benomyl (2.89% DS). The data on systemic - protectant fungicide treatment were not significantly different (P<0.05). Bupirimate when combined with protectant fungicide either chlorothalonil (0.46% DS) or mancozeb (0.34% DS), and tank mixes of benomyl with chlorothalonil (0.91% DS), and with mancozeb (0.34% DS) proved to be very effective in the control of powdery mildew of butternut squash as compared to all other fungicidal treatments.