症状：施用化肥过量，须根和细根变红褐色，逐渐腐烂；主根皮层变褐色坏死。坏死皮层 多沿根颈部向上扩展到主干、主枝、侧枝以至梢部，与健皮交界处明显，常呈带状。严重的 可使果树整株枯死。发生规律：将过量化肥埋于树根附近或施肥沟离根颈太近，把大量化肥倒放沟内，或施? Symptoms: excessive use of fertilizers, fibrous roots and reddish brown roots, gradually decay; the main cortex brown necrosis. Necrosis of the cortex along the root of the neck up to extend to the trunk, main branch, collateral and even the tip, and the junction of healthy skin obvious, often strip. Serious can make whole fruit tree dead. The law occurs: the excessive fertilizer buried in the roots near the roots or fertilization ditch too close to the root of the neck, put a large amount of fertilizer down the ditch, or Shi?