Abstract:

This paper reported the symptoms, pathogen and pathogenic mechanism of the leaf brown spot and its control methods and their effects for the improved varieties Kerman and Peters of Pistacia vera introduced in 1997—2006 in contrast with Xinjiang Pistacia vera. The result showed that during disease occurrence, macroscopic, brown, circular or irregular lesion on both surface of the leaf occurred, and in severe cases leaves became massive scorch and yellow. According to the isolates from infected leaves, its pathogen has been verified to be fungi of Alternaria sp. And Cerospora sp. Monthly average temperature above 30℃ and air relative humidity 64%～70% accelerated occurrence and development of this disease. Disease severity was relevant to tree vigor and growth conditions. The cultivars Kerman and Peters showed higher resistance. Usually, trees which grow stronger and in soils rich in P (1.750 3 g·kg^-1), and containing relatively high level of Cu and B didn't suffer from the disease. But planting in high-density with leaf area index (LAI) over 7, tree were prone to be infected. Based on studies on the disease, the authors summarize that control measures should be taken as major considerations for its effective; controlling irrigation strictly in accordance with soil natural water content(15%～20%) and air relative humidity (60%) at growth stages. Moreover, planting improved varieties with strong seedlings in reasonable density, and spraying once a week fungicides (0.2% carbendazim or 0.2% thiram in turn),and fertilizers(0.5%(NH₄)₂HPO₄ or 0.5% K₂HPO₄), with dosage of 0.5 kg·m^-2 can keep disease index below 6%.

Key words: Beijing area, Pistacia vera, leaf brown spot, control