How to prevent and control dry rot in apple cultivation
Apple dry rot, also known as trunk rot, is one of the important diseases of apple trees.
1. Symptoms
When young trees are affected, dark brown to blackish-brown lesions initially form near the grafting site, spreading upward along the trunk and potentially causing death in severe cases, with many raised small black dots on the lesions. When large trees are affected, moist, irregular dark brown lesions are mostly scattered on the branches and trunk, and the diseased area exudes a dark tea-colored mucus. When the lesions develop longitudinally along the branches, they can affect the entire branch or trunk in severe cases; in the later stage, the lesions lose water and form distinctly sunken dark brown dry patches. The junction between diseased and healthy tissue often cracks, and the diseased bark curls up and peels off, with many small, dense, raised black dots appearing on the surface of the lesions. In severe cases, the bark tissue dies, eventually rotting down to the xylem, and the entire branch or trunk dies.
When fruit is affected, brown spots first appear on fruit on the sunny side in the upper part of the canopy; after enlarging, they become round or irregular light brown lesions, gradually expanding into concentric ring-shaped lesions. Under suitable conditions, the lesions spread rapidly and can cause the entire fruit to rot within a few days. In the later stage, black dots may appear on the surface of the lesions.
2. Prevention and control methods
① Strengthen cultivation management, deep plow and improve the soil, apply more organic fertilizer, drain and irrigate in a timely manner, enhance the disease resistance of the tree, and minimize wounds on the tree.
② Remove diseased and dead branches from the tree and burn them in a centralized manner.
③ Scrape off the diseased bark; after scraping, apply a 50-fold dilution of 40% asomate.
④ In late autumn and early winter or before bud break in early spring, spray the whole tree with a 100-fold dilution of 40% asomate to clean the orchard and eliminate the pathogen. During normal times, combine with the control of other diseases by spraying Bordeaux mixture, chlorothalonil, etc.
⑤ To prevent fruit infection, refer to the control methods for apple ring rot.