梨是陕西省渭南市的主要水果栽培树种,种植面积已超过1.67万hm2,总产量超过50万t。连续几年出现的连阴雨气候,加之梨种植管理普遍粗放,导致果园密闭,通风透光差,使梨黑星病病原菌基数增大,发病严重。1997年病园率达70%～80%,病叶率达30%～40%,使667hm2梨失去了经济价值;1998、1 Pear is a major fruit-growing tree species in Weinan City of Shaanxi Province, with an area of ​​more than 16,700 hm2 and a total output of more than 500,000 t. Continuous rainy days in successive years, coupled with widespread perennial planting and management of pear, resulting in closed orchard, ventilation and poor light, so that pear scab pathogens base increased, the incidence of serious. In 1997, the rate of diseased garden reached 70% -80%, and the diseased leaf rate reached 30% -40%, which made the 667hm2 pear lose its economic value. In 1998,1