Distribution of Pistachio Die-Back in Khorasan-Razavi Province and Application of Some Fungicides for the Disease Control

The die-back of pistachio is one of the most important diseases affecting pistachio trees reducing yield production. In commercial fields, sampling was done from nine different pistachio production areas in Mahvelat, Khorasan Razavi province during 2008-2010. In each orchard, samples were taken from tree branches with canker during spring and summer seasons. Fungal species were identified based on the micro and macromorphological features, reverse and surface characters of colonies. The ability of the isolates to produce disease was assessed on two year-old pistachio branches. The effect of Mancozeb, Benomyl, Metalaxyl, Rovral TS, Bordeaux mixture and Propiconazole was evaluated on radial mycelia growth of P. variotii, N. mangiferae and Stemphylium spp.. In most orchards, the samples were positive for fungal species and in only a few orchards no fungal isolates could be detected. Based on micro and macro- morphological features; P. variotii, N. mangiferae, and Stemphylium spp. were identified in most sampling areas with different frequencies. In pathogenicity tests, most isolates of N. mangiferae and Stemphylium spp. were able to establish disease, while about 43 % of P. variotii isolates produced die-back on inoculated branches. The results of fungicides produce different levels of control on mycelia growth of fungal species which was varied according to the kind of fungicide and fungal species. Overall, the differences between fungal isolates, biotic and a biotic factors to produce disease as well as contradictory results were obtained by different researchers as described in literature.