Control Methods and Technical Key Points for Apple Little Leaf Disease

Apple little leaf disease occurs mostly in orchards with poor soil and good permeability. Because of low zinc content, soluble zinc salts leach away and the disease becomes severe; frequent watering and rainfall cause large losses of soluble zinc; excessive nitrogen fertilizer use increases the tree's zinc requirement; in saline-alkali soil the pH is relatively high, zinc is easily fixed and cannot be absorbed by the root system. In addition, heavy clay soil, a shallow living soil layer and poor root development lead to severe little leaf disease. Therefore, increasing the supply of zinc salts or releasing fixed zinc elements is an effective way to control this disease. The specific methods are as follows:

Apply more organic fertilizer to improve the soil and increase the organic matter content in the soil; this can lower soil pH, increase the solubility of zinc salts and make it easier for fruit trees to absorb them. For orchards with poor conditions such as sandy land, clay land and saline-alkali land, the soil should be improved by applying more farmyard manure to increase zinc elements and release fixed zinc elements, which can promote well-developed roots and improve absorption capacity.

Combine soil zinc application and plant zinc spraying with the application of base fertilizer. Apply 0.1-0.15 kg of zinc sulfate per tree as a top dressing; after application it generally takes effect the following year and can last for 3 years. For fruit trees with little leaf disease, spray a 30-fold zinc sulfate liquid fertilizer on the tree before bud break, which has an obvious effect on preventing little leaf disease in the current year. 3 weeks after flowering, if diseased plants with little leaf disease are found, spray a mixed solution of 500-fold zinc sulfate plus 300-fold urea, which has an obvious effect on reducing the disease. Spraying for 2 consecutive years gives a recovery rate of diseased branches of more than 95%, and the yield also increases noticeably.