What are the latest control methods for apple tree yellow leaf disease?
Apple tree yellow leaf disease is a common disease of apple trees, also known as chlorosis, iron deficiency chlorosis, etc. It is a physiological disease caused by a lack of iron. It starts from the young tender leaves of new shoots, the leaf mesophyll turns yellow first, the veins remain green forming a green net-like pattern, and later the whole leaf turns yellow-white, the leaf margins scorch, and finally the whole leaf dies and falls early. Now let us take a look at what to do about apple tree yellow leaf disease!
Causes of yellow leaf disease
Apple trees cultivated in saline-alkali soil or soil with excessive lime are prone to yellow leaf disease, especially when alkaline soil has too much moisture, the disease is severe. When fruit trees grow vigorously and encounter sustained drought, and the soil salt content is too high, the disease is severe. After entering the rainy season, yellow leaf disease lessens or disappears. Orchards with a high groundwater table, low-lying land and heavy clay soil are prone to the disease. Using Northeast crabapple (Malus baccata) as rootstock, chlorosis is severe in saline-alkali areas.
Spraying compound iron fertilizer solution
Preparation of compound iron fertilizer solution: first add 50 g of citric acid to 50 kg of water, and after the citric acid dissolves, add 150 g of ferrous sulfate and stir thoroughly. After the ferrous sulfate dissolves, add 100 g of urea. Spraying method: spraying the compound iron fertilizer solution is best done before 10 a.m. or after 4 p.m. The mist droplets should be fine, and the spraying should be even and thorough.
Injecting fruit tree re-greening agent
Injecting fruit tree re-greening agent is suitable for large apple trees over 5 years old. First drill holes in the apple tree, with a hole diameter of 7 mm and a depth of 5-6 cm. Generally, one hole is drilled every 120 degrees around the trunk, with 3 holes per tree. Use a wire hook to clean out the wood chips, hammer the sprayer outlet fitting into the drilled hole, then fill a treadle sprayer with the diluted fruit tree re-greening agent, a 20-fold solution prepared with distilled water or soft water (or a 0.05-0.08% ferrous sulfate aqueous solution), connect it to the outlet fitting, and injection can begin. Inject 1 liter per mature tree; young trees in the initial fruiting stage can be appropriately reduced.
Applying more organic fertilizer to fruit trees
During the dormant period of fruit trees, mix ferrous sulfate with organic fertilizer in proportion to make organic iron fertilizer and apply it to the soil, or spray compound iron fertilizer solution on the leaves in the early growth stage, or forcefully inject fruit tree re-greening agent into the trunk; the effect of preventing and controlling apple yellow leaf disease is relatively good. Mix ferrous sulfate with high-quality thoroughly decomposed organic fertilizer at a ratio of 1:15. When preparing, first dissolve the ferrous sulfate in 10 times its amount of water, then spray the ferrous sulfate solution onto the organic fertilizer while turning and mixing it with a shovel so that it is fully and evenly mixed. First dig a ring-shaped trench along the outer edge of the tree canopy, with a trench depth of 50 cm and a width of 60 cm, then evenly apply the mixed organic iron fertilizer into the trench, cover with soil, and water immediately. Generally, large trees over 10 years old are given 80-100 kg per tree, and young trees under 10 years old are given 30-50 kg per tree. Organic iron fertilizer is best applied in autumn when applying base fertilizer, and can also be applied before fruit trees sprout, but it must not be applied during the growing season to avoid phytotoxicity.