Apple dry rot is also called dry rot. It mainly harms the main branches and lateral branches, but also the trunk, branchlets and fruits. Fragile old trees and young trees that are poorly managed after planting are more vulnerable. Young trees are infected with diseases, which mostly occur shortly after planting in early spring, that is, the slow seedling stage. At first, reddish-brown or dark-brown spots are produced at the joint and spread upward along the trunk. In severe cases, young trees wither and die, and many slightly prominent black spots, namely pathogen conidia, are produced at the wound. Lesions in the upper trunk initially produce dark brown, oval or plastic lesions. Contraceptive pills swell up and down in the trunk, forming strip spots and cracks at the junction of disease and health. When the branches are surrounded by diseased spots, young trees die and many small black spots are produced in the diseased parts, which is an important feature of the disease. When the tree is sick, irregular reddish-brown spots are formed on the trunk at the beginning, the surface is wet, and brown mucus overflows from the diseased part; After the lesion expands, the water in the affected area gradually loses, forming dark brown dry spots with obvious depressions. There are many prominent small black spots on the affected area. When mature, it breaks through the epidermis and is exposed. The particles are small and dense, with a small opening at the top. This is the obvious difference from rot. In severe cases, the diseased spots are linked together, all bark tissues die, and finally rot to xylem, and the whole branch shrinks and dies. Sometimes it only happens on one side of the branch, forming concave strip spots, and the trunk dies quickly. Aging apple trees often get sick on the upper branches. At first, purple-brown or dark-brown spots are produced on the diseased branches, and the diseased parts rapidly expand to the xylem, eventually making the whole branches dry and die, and the diseased parts densely produce black particles in the later stage. The fruit was infected, and it was yellow-brown at first. Gradually expand into concentric wheel patterns, which are difficult to distinguish from wheel pattern spots. Under suitable conditions, the disease spots spread rapidly, causing the whole fruit to rot in a few days.

Transmission route and pathogenic conditions: The pathogens mainly overwinter in the diseased bark with mycelium, conidia and ascomycetes, and the pathogens spread directly along the diseased part in the next spring, or conidia or ascospores were infected, mostly from wounds or dead buds or lenticels. The parasitic effect of the strain is weak, and it can only invade seedlings or weak trees at the slow seedling stage, which has the characteristics of latent infection. Generally speaking, fungi will grow on the wound tissue of branches for a period of time, and then spread to living tissues. After the planted saplings turn to normal growth, the disease stops spreading. Spores are spread by wind and rain. Dry rot pathogen is also the weakest parasite. When the disease is serious in dry year or dry season and the bark moisture is lower than normal, the bacteria spread rapidly, and the low-lying land accumulates water and the rainfall is uneven. Poor management of soil fertilizer and water, heavy salinity, many wounds and many fruits are all conducive to the occurrence of dry rot. Diseases often occur when there are many droughts or heavy rains that seriously affect the tree potential. Among all apple varieties, Jinguan, Guoguang and Fuji suffered the most, while Redjade, Marshal, Jiguan and Zhuguang suffered less. Dwarf anvil M9 is seriously ill. The disease can occur in the growing period of apple, and it is the most serious in June-August and June 5438+00.

Control methods: (1) Select and plant disease-resistant varieties. (2) Strengthen cultivation management and enhance tree vigor. Improve soil, improve soil water retention capacity, irrigate in dry season and prevent waterlogging in rainy season. At the same time, it is necessary to protect the tree from freezing injury and insect pests, and apply drugs to the existing branch wounds to promote wound healing and prevent the invasion of germs. Seedling planting should avoid deep planting, make the joints flush with the ground, and fully irrigate to shorten the delay of seedling emergence.