The latest course on Prevention and Control of Apple Tree Rot

Apple tree rot is one of the more serious diseases in apple producing areas in China, commonly known as smelly skin disease, skin rot disease, skin rotting disease and so on. Apple tree rot is very serious in northern China, with numerous scars and incomplete branches. often cause dead trees and destroy the garden, there is a trend of aggravation in recent years, let's take a look at the prevention and control techniques of apple tree rot.

Symptoms caused by apple tree rot

The branches of diseased trees are damaged, and the disease spots can be divided into two types: ulcer and branch withering. The ulcerative part of the disease is reddish brown, watery, slightly raised, the diseased tissue is soft and rotten, often exudes yellowish-brown juice, has the smell of wine lees, shrinks and sinks in the later stage, and the disease has obvious small black spots (that is, conidia). An orange tendril emerges from the small black spot when it is wet. Branch withering type mostly occurs in branchlets, fruit platforms, dry piles and other parts, the diseased part does not show waterlogging, rapid water loss and drying up, resulting in the death of the whole branch, upper black small grain spots. The fruit is damaged, the spot is dark reddish brown, round or irregular, with wheel lines, soft rot, slightly alcoholic smell, and there are often obvious small black spots in the middle of the spot.

Transmission route of apple tree rot

Apple tree rot is mainly overwintered by mycelium, conidium and ascomycete in diseased tree tissue and remnant, and the pathogen can survive in the diseased part for about 4 years. In the following year, conidia were excreted from the conidia, which were spread by Rain Water spatter and invaded from the wound. The pathogen has the characteristic of latent infection, and it will spread when the tree or its local tissue is weak. In general, the infection began from March to May, and the disease began from July to August. The disease peaked in early spring, and the disease resistance increased and the incidence decreased sharply after late spring. The occurrence of apple tree rot is closely related to tree potential, number of wounds and callus ability. Extensive management and periodic freezing injury are the main epidemic factors.

Disease conditions of apple tree rot

The optimum temperature for the germination of conidia and ascospores of rot pathogen was 25 ~ 30 ℃, and it could germinate for a long time under the condition of 5 ℃. Extensive cultivation and management and freezing injury are the main causes of the epidemic of rot. The orchards with low soil organic matter, soil consolidation or poor water and fertility conservation, poor root growth, insufficient compound fertilizer, partial application of nitrogen fertilizer, too many results, serious years, early defoliation and so on, the disease is more serious, and vice versa. In the late low-lying orchard, the time of stagnant water in orchard is too long, the dormancy period is delayed, and the orchard is vulnerable to frost damage, and the disease is also serious. Periodic frostbite in northern China, resulting in a large area of bark frostbite, is an important reason for the widespread epidemic of rot.

Control techniques of apple tree rot

1. Strengthen cultivation and management: disease resistance of strong trees, reasonable pruning, adjustment of tree potential, adjustment of tree load, overcoming the phenomenon of big and small years, increasing application of organic fertilizer, reasonable collocation of nitrogen, phosphorus, potassium fertilizer and medium and trace elements, preventing cold of fruit trees, reducing freezing wounds, whitening fruit trees, commonly used whitening agent, lime: salt: water: animal oil (10, 1, 15, 30, 30, 35, 0.2), generally after fruit trees are defoliated. The drying height is 2 meters.

2. Timely cleaning of orchards: timely cleaning of orchards can reduce germs, scrape off diseased spots in time, remove diseased branches, stumps and diseased fruit tables when pruning, remove and burn diseased branches and dead trees in time, and seal saws and other wounds with chemicals or paints to reduce pathogens infection.

3. Medicament prevention: fungicides are sprayed before tree germination in early spring, including 500 times solution of Gerun or Schenanin water agent, 3% 5 degree stone sulfur mixture, 500 times liquid of 5% bacteriological dehydrated water agent, etc., and the above chemicals can be used to brush the big branches of the tree from June to July. Control has obvious effect for several consecutive years.

4. Treat with scar.

① curettage: extend 0.5cm around the scar and cut a protective ring deep into the xylem with a knife, then scrape off the diseased skin and healthy skin thoroughly, scrape off the diseased tissue on the plastic sheet and burn it. The exposed xylem was cut 1-1.5 cm deep with a knife and then treated with medicine. It can be smeared with Grun 5 times solution, 5% bacteriological detergent 5 times solution, and apply again 20 days after treatment.

② mud application method: make a mud cake with water and mud, apply to the scar and its periphery 5-8 cm, 3-4 cm thick, and then fasten it with plastic sheet or Kraft paper. This method should be carried out in spring, remove the bandage in the following spring, and apply disinfection protection after removing the diseased and disabled tissue.

③ foot connection: the use of foot connection (or bridge) can improve the transport capacity of the tree to nutrition and water, which is beneficial to the restoration of tree potential, and can prolong the fruiting life. This method is widely used in old fruit areas, and new fruit areas can be actively popularized.