Symptoms and Treatment of Yellow Leaf Disease in Apple Trees
Apple leaves turning yellow is not only a normal phenomenon of growth and metabolism, but may also be caused by yellow leaf disease. There are many reasons for leaves turning yellow, and they must be correctly distinguished to treat the disease with the right remedy. Once affected, it will impact the yield and quality of apples, which is a very serious problem for fruit growers. So what symptoms appear when apple trees suffer from yellow leaf disease? How can it be cured?
1. What symptoms appear when apple trees suffer from yellow leaf disease?
Once yellow leaf disease occurs in apple trees, it starts from the young leaves at the new shoot tips. At first, the leaf tissue turns yellow while the veins remain green. As the yellow leaf disease develops more severely, the entire leaf blade becomes yellow-white. In severely affected apple trees, the entire leaf edge is scorched and withered, and even the tips die off directly, affecting the normal growth of the fruit tree.
The severity of yellow leaf disease in apples is related to soil texture. Generally speaking, most cases of apple yellow leaf disease are caused by a lack of iron in the soil, resulting in iron deficiency in the apple tree. In sandy soil, the disease incidence is lower, while saline-alkaline soil or soil with too high a lime content prevents apple trees from absorbing iron.
The severity of yellow leaf disease in apple trees is also related to the type of rootstock. Those that are alkali-resistant are relatively sensitive to iron deficiency. Apple trees using Shan Ding Zi as rootstock have more severe yellow leaf disease, while apple trees using crabapple as rootstock have milder yellow leaf disease.
2. How can yellow leaf disease in apples be cured?
1. Improve the nature of the soil
Plant leguminous forage grass in the apple orchard, then increase the use of organic fertilizer. This can improve soil aeration and the soil's physical and chemical properties, thereby enhancing the activity of root microorganisms.
2. Increase the use of organic iron fertilizer
Before apple trees bud or when applying base fertilizer in autumn, ferrous sulfate can be added. Remember, it must not be used over the long term. The specific method is to mix ferrous sulfate and decomposed organic fertilizer at a ratio of 1 to 15, stir evenly, then dig a ring-shaped trench 50 cm deep and 70 cm wide along the outer edge of the apple tree canopy, place the already mixed organic iron fertilizer into the trench, and water thoroughly immediately after covering it with soil. The specific amount to use depends on the age of the plant. A young apple tree needs about 30 kg each, and a 10-year-old large tree needs about 80 kg of organic fertilizer each.
3. Apply foliar fertilizer
Foliar fertilizer should be determined according to the leaf growth stage of the apple tree. During the young leaf stage, amino acid iron, compound iron fertilizer liquid, etc. can be applied. During the vigorous growth stage, foliar fertilizer must be used reasonably to avoid excessive fertilization causing leaves to wither and turn yellow.
4. Comprehensive management
Do a good job of soil improvement in the orchard, select disease-resistant rootstocks, and pay attention to drainage in low-lying orchards to prevent excessive water accumulation and root rot.