Control of Silver Leaf Disease of growing Apple

Apple silver leaf disease is distributed in all apple producing areas in China. It mainly occurs in apple producing areas along the old route of the Yellow River in Jiangsu, Anhui and Henan provinces, while other apple producing areas are rare. It is a destructive disease, which can cause the whole apple tree to die when the conditions are right.

[identification characteristics] the typical symptom of apple silver leaf disease is that the leaves are silver gray and metallic luster. The symptoms can be divided into two types: typical silver leaf and concealed silver leaf.

(1) typical silver leaf: the leaf surface is like coated with a silver gray film, the leaf is small, thick and brittle, and the epidermis is easy to separate from the mesophyll. In the later stage, the edge of the diseased leaves was scorched, rust spots appeared along the main vein, and the diseased leaves were broken and easy to fall off.

(2) concealed silver leaves: mainly occur in newly diseased trees or trees with reduced disease after treatment. The leaves faded, resulting in uneven fish-scale gray, green and yellow markings. Do not blossom or blossom less, set fruit very little, the fruit is small and light.

Apple silver leaf disease generally developed from the branchlet to the main branch, and gradually spread to the whole plant. It usually occurs on weakening trees, where severe trunk and root xylem turn brown, resulting in root rot and death and the death of the whole tree.

[occurrence characteristics] Apple silver leaf disease is a disease caused by fungi. The pathogen overwinters with hyphae in the xylem of diseased branches, or the fruiting body outside the bark. In the apple producing areas in the old route of the Yellow River, diseased branches produce fruiting bodies twice in May-June and September-October every year. Basidiospores are produced after maturity, which spread with wind and rain and invade from sawing or other wounds, as well as from leaf scars and lenticels. When the weather is wet, the spores germinate and infect the xylem, producing a toxin that browns the xylem and gradually spreads to all parts of the tree. The number of diseased trees was the most from April to May, and the diseased trees appeared symptoms one after another after June. Its occurrence is closely related to orchard topography, variety and tree age. In general, the soil on the flat land is heavy, the drainage is poor, and the disease is serious in the orchard with weak tree potential.

[integrated prevention and control]

(1) to eliminate the source of bacteria: it is necessary to clean the countryside in time, eradicate seriously sick and dead trees, remove dead branches and burn them centrally. After precipitation, the inspection should be strengthened to scrape off the fruiting bodies from diseased trees and other trees near the orchard and burn them centrally. And smear the disease department with 40% formaarsine 100 times solution or 1% copper sulfate solution to reduce the spread of germs.

(2) reduce wounds: when shaping fruit trees, we should pay attention to cultivate solid backbone branches, control the load, prevent branches from breaking due to too many results, and reduce mechanical wounds as much as possible. the cut and wound should be protected by smearing 5 Bomedo stone sulfur mixture or 40% formearsine 100 times solution.

(3) strengthen the cultivation management: increase the application of organic fertilizer, improve the soil, timely drainage, prevent the orchard from stagnant water, in order to enhance the tree potential and improve the tree disease resistance.

(4) Chemical control: the lightly diseased trees found in the early stage can be buried in the diseased branches with sulfuric acid-octahydroxyquinoline pills. The specific method is to use a punch to punch a hole 1.5 cm in diameter and 3 cm deep at the base of the diseased branch, bury the pill, and seal it with a cork or wax. When the branches are thicker, they can be spirally staggered and punched according to the distance of about lO centimeters, and 1 gram of medicine is buried in each hole.