果树黄化病也叫黄叶病、失绿症等,症状是:初期只有叶肉发黄而叶脉仍保持绿色,只是在新梢生长初期不太明显,到后期则幼叶叶片黄化,而老叶仍为绿色。严重时,从上到下枯死,树冠逐渐缩小,最后死亡。因而直接影响到果树的寿命和产量。引起果树黄化病的原因,从外因来讲,是土壤中含铁量小于果树的利用量。但一般土壤中含铁不少,由于其它元素的影响,变为不可利用状态。如碱性土壤中铁易和氢氧根离子结合成不溶性氢氧化铁;土壤中 pH Yellowing disease of fruit tree is also called yellow leaf disease, chlorosis and so on. Symptoms are as follows: the only yellow leaves in the beginning and the veins still remain green, but not obvious in the early growth of new shoots, The leaves are still green. Serious, dead from top to bottom, crown gradually narrowed, and finally died. Which directly affects the life span and yield of fruit trees. The cause of yellowing of fruit trees, from the external terms, is the amount of iron in the soil is less than the amount of fruit trees. However, a lot of iron in the soil generally, due to the impact of other elements, become unavailable. Such as alkaline soil easily iron and hydroxyl ions into insoluble iron hydroxide; soil pH