What to Do About Yellow Leaf Disease in Apple Trees? A Detailed Guide to Prevention and Control Methods
Yellow leaf disease in apple trees 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 mesophyll turns yellow first, while the veins remain green, forming a green net-like pattern; later the entire leaf turns yellow-white, the leaf margins scorch, and finally the whole leaf withers and drops early. Let us take a look below at what to do about yellow leaf disease in apple trees!
Causes of yellow leaf disease
Apple trees grown in saline-alkali soil or soil with excessive lime are prone to yellow leaf disease, especially when alkaline soil has too much water, in which case the disease is severe. When fruit trees grow vigorously and encounter prolonged drought, and the soil salt content is too high, the disease is severe; after the rainy season arrives, yellow leaf disease lessens or disappears. Orchards with a high groundwater table, in low-lying land, and with heavy clay soil are prone to the disease. When Malus baccata (Siberian crabapple, known in China as Shandingzi) is used 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; 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: spray the compound iron fertilizer solution preferably before 10 a.m. or after 4 p.m. The mist droplets should be fine, and spraying should be even and thorough.
Injecting fruit tree regreening agent
Injecting fruit tree regreening agent is suitable for large apple trees 5 years old or older. First drill holes in the apple tree, with a hole diameter of 7 mm and a depth of 5-6 cm; generally one hole per 120-degree angle around the trunk, with 3 holes per tree. Use a wire hook to clean out the wood shavings, hammer the water outlet connector of the sprayer into the drilled hole, then fill a treadle sprayer with the diluted fruit tree regreening 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 water outlet connector, and injection can begin. Inject 1 liter per mature tree; for trees in the initial fruiting stage, it may 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 strongly inject fruit tree regreening agent into the trunk. These have relatively good effects in preventing and controlling apple yellow leaf disease. Mix ferrous sulfate with high-quality 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 uniform. 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 prepared organic iron fertilizer into the trench, cover with soil, and water immediately. Generally, for large trees over 10 years old, apply 80-100 kg per tree; for young trees under 10 years old, apply 30-50 kg per tree. Organic iron fertilizer is best applied when applying base fertilizer in autumn, and may also be applied before fruit trees sprout, but it must not be applied during the growth period, so as to avoid phytotoxicity.