近年来,南丰蜜桔普遍出现黄叶枯梢症状,产量下降到只有正常年景的三分之一,个别园甚至连续数年绝收,且树势逐年衰弱,濒于死亡。经调查确诊为缺素症,其表现症状:春叶轻绿时,叶面出现水渍状黄色透明斑点,以后逐渐扩大增多,沿叶尖叶缘向内发黄,斑点部出现黑褐色胶状物,最后叶脉黄化,病叶自枝梢顶部逐渐向基部脱落,枝梢亦枯死至落叶处。残存未落病叶,老熟后叶脉肿大破裂,并溢出黑色胶状物,叶身变厚,脆而较硬,叶面不平。病果果皮增厚,果面粗糙,呈瘤状,有流胶现象,果小而硬,内瓤干缩,渣多汁少。病株落花落果严重,根系 In recent years, the phenomenon of yellow-green leaves often appears in Nanfengmilk, the yield drops to only one-third of the normal years, and individual gardens are even inaccessible for several years, and the tree vigor weakens each year and is nearing death. The survey confirmed the lack of symptoms, the performance of symptoms: light green leaves, the water-like leaves appear yellow transparent spots, and then gradually expanded to increase along the tip of the leaf edge yellowing, spot dark brown gum The last leaf veins yellow, diseased leaves gradually from the top of the shoots to the base off, shoots are also dead to the leaves. Remnants of diseased diseased leaves, ruptured old veins enlargement, and spilled black jelly, thicker leaves, brittle and harder, uneven leaves. Fruit peel thickened, fruit surface roughness, tumorous, the phenomenon of plastic flow, fruit small and hard, dry nephew shrinkage, juicy slag less. Diseased plants fall severely, roots