Scab disease of peach and nectarine and its management

Scab caused by Cladosporium carpophilum Thum. is a serious disease of peach and nectarine in lower Kullu valley of Himachal Pradesh and known to occur in varying proportions since 2005. The primary infection of the expanding twigs and developing fruits in the spring results solely from conidia produced in 1-year old twigs. The studies have revealed that the conidial production on twig lesions commences around bloom, peaks at pea stage of fruit development and ceases at around fruit development stage (70–74 days after bloom). For the control of the disease nine different fungicides were evaluated for three successive seasons (2007–2009) to find out the best suitable ones. The fungicides, captan (0.3%), sulfex (0.2%) and chlorothalonil (0.2%) provided maximum disease control ranging from 83.4 to 90.6 per cent on peach and 85.3 to 87.4 per cent on nectarine fruits and were statistically at par. These treatments were also highly effective in reducing the development of twig lesions during the season there by had significant role in reducing the over wintering inoculums. The studies on the influence of fungicidal treatments on fruit quality have revealed that the skin colouration was better in fruits from captan and chlorothalonil treated plants as compared to sulfur treated plants both in peach and nectarine. At harvest, the sulfur treated fruits were firmer than fruits from trees sprayed with captan and chlorothalonil but had comparatively less total soluble solid concentrations.