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Unconsciously, March is approaching, although the temperature is still cold in recent days, but I believe that at the beginning of spring, everything is about to recover. Spring is a critical period for fruit tree management, and apple trees enter the germination period. The prevention and control of two diseases during this period is very important, and if properly controlled, the next year will be a lot of worry. That's rot and rust.
1. Rot disease
1. Symptoms of morbidity
Apple rot disease has two more typical symptoms, namely ulcer type and branch wilt type. In the southern region, due to the higher rain and higher air humidity, ulcerated types are more common, but not absolute. The ulcerative type is mainly manifested by the appearance of sunken, wet and soft reddish-brown spots on the surface of the branches, usually round or oval; in the later stages, many small black particles are distributed on the spots, and white heads appear; when wet, the spots will overflow with yellow-brown juice from the lees. The shoot-type disease spots are not water-stained, and after losing water, they dry up, and they are also densely packed with small black grain spots.
2. Incidence
Rotting bacteria lurk, move and spread between November and February in the bark and xylem surface of apple trees. When spring begins in March of the following year, when the temperature is right, it will be damaged by skin holes, fruit stalk marks, leaf marks and various wounds invading the fruit tree, resulting in ulcer spots. Apple rot has two peaks in spring and autumn, March-April and July-September. When the disease is mild, the bark rots, the tree declines, and the yield and quality of apples decrease. When the disease is severe, it causes the trunk and the whole tree to die, and even causes the destruction of the garden; apple rot disease is also known as "apple cancer".
3. Prevention and control methods
Rot is more common on fruit trees with more wounds, for example, we found that the incidence of frost-damaged apple trees is higher, and it is precisely because frost damage has caused many cracks in the surface of fruit trees. Therefore, if the fruit tree is damaged by frost, or has undergone pruning, it is necessary to pay attention to the protection of the wound. Use 75% Bacillus Clear Wettable Powder 500-600 times liquid, stone sulfur compound crystal dilution 20-30 times, etc. to spray or apply sterilization to disinfect the wound. Larger wounds should be wrapped in plastic film or covered with turpentine.
In addition, the main trunk and large branches can be applied with bactericidal pesticides such as 38% evil cream anchovylate 600-800 times liquid between March and April, which can play a good preventive effect. If the spots are found, be sure to scrape and scrape in time to avoid the expansion of the spots, apply 45% of the 100 times liquid of shi na ning or 50 times of the 843 rehabilitation agent for disinfection protection after scraping, and apply the entire scar with tight seams.
Second, rust
1. Symptoms and hazards
Rust mainly harms the leaves, the surface of the affected leaves appear orange-yellow small spots, with the development of the disease, the spots gradually expand, becoming a nearly circular pale yellow spots, the outer ring surrounds a layer of yellow-green halo ring. Orange-yellow particles the size of pinholes accumulate on the front of the plaque, which turn black later in the disease. The dorsal surface of the plaque is slightly raised, and later the center of the plaque becomes black, and the outer ring is yellowish-green. The disease spots often cause the leaves to scorch, curl, and fall early. If the control is not done properly, the young shoots and fruits will also feel sick in the later stages. The branches are manifested as orange-red spots, which are concave, cracked and easily broken in the later stages, and after the fruit is diseased, the spots become brown and small black spots appear in the center, resulting in fruit deformity and hair growth in the later stage.
The germs of rust come from the surrounding cypress plants such as juniper trees and cypress trees; apple orchards without cypress trees within 5 kilometers are almost rusty. In winter, the pathogen overwinters in the branches of juniper and cypress trees ("gum flowers"), and in the spring, it spreads with the wind to the apple trees and invades. The occurrence of rust is greatly affected by spring temperature and humidity, high temperatures in February and March, rain is conducive to the survival and spread of germs, and when apple trees germinate, dry weather is often mild. Therefore, the temperature from February to March, the amount of rain after the young apple leaves are unfolded, and the presence or absence of cypress trees nearby are important factors affecting the occurrence of diseases in that year.
After the beginning of spring in March, from the beginning of the apple leaf spread period, spray the fungicide every 10-15 days, 2-3 times in a row, which can protect the leaves from rust bacteria. The fungicide can use pentazole, flusilazole, pyrazoprazole, nitricomazole, ethermethoxazole, triazolone, and other triazole pesticides. If there are cypress trees within 5 kilometers of the surrounding area, it is best to spray them for sterilization if conditions permit, and spray 2-3 baumedo stone sulfur compounds. It is also possible to cut off the orange-red "gum flower" (gall) of the cypress tree in the form of agar and cockscomb in time, and carry out centralized destruction to reduce the base of rust on the cypress.