一、为害特点:北方梨区广泛发生,其中以东部沿海地区和内陆低洼盐碱区发生较重,往往是成片发生,在中性沙质壤土上也有不同程度的发生。症状都是从新梢叶片开始,叶色由淡绿变成黄色,仅叶脉保持绿色,严重发生的整个叶片是黄白色,在叶缘形成焦枯坏死斑。发病新梢枝条细弱,节间延长,腋芽 First, the damage characteristics: North pear widely occurred, of which the eastern coastal areas and inland low-lying saline-alkali area occurred heavier, often into a film occurred in the neutral sandy loam have varying degrees of occurrence. Symptoms are from the shoot tip leaves, the leaf color from light green to yellow, only the veins to maintain the green, the serious occurrence of the entire leaf is yellowish white, the formation of focal necrosis in the leaf margin dead spots. The shoot tip thin, internode extension, axillary buds