Apple Alternaria deciduous disease is another serious disease in early defoliation after the occurrence of brown spot disease in recent years.
1, the incidence characteristics. Compared with brown leaf spot, gray spot disease, round spot disease and other early defoliation diseases, it has the following characteristics: 1 early onset and rapid spread. 2 strong drug resistance. After many years of production experience, it has been proved that the Bordeaux mixture has particularly obvious control effects on early defoliation diseases represented by brown spot, but it has almost no bactericidal effect on apple deciduous disease. 3 There are many lesions and there is a phenomenon of expansion joint. In late May, the onset and spread of new shoots, a number of lesions up to a few leaves, weighing more than 10, after the rapid formation of lesions, resulting in a short time leaves dry, fall off. There is a large difference in disease resistance among the 4 varieties. The Marshal is onset and the Fuji Department is light.
2, symptoms. The disease mainly damages the leaves and also harms the shoots and fruits. Leaves are vulnerable to damage within 20 days. Brown spots appear on the leaves at the onset of the disease. There are purple brown halos around. When conditions are right, several lesions are connected, and finally the leaves dry off. When the weather is wet. Black mold layer grows behind the lesion. After the young leaves are infested, the leaves are shrinking and deformed. After the petiole and the tender shoots are damaged, an oval-shaped brown sunken lesion is generated, resulting in easy detachment of the leaves and easy breakage of the twigs and easy drying. When the fruit is damaged in the near mature stage, brown spots appear on the fruit surface, and the fruit suffers. The dark brown mold layer can be expanded to the flesh.
3, the incidence of law. In the middle and early June, the initial infection period of the pathogenic bacteria occurred. The peak period of onset was from July to August, and it was always endangered until mid-October. The occurrence and prevalence of the disease are closely related to climate and species. It is prone to hot and rainy conditions, the drought year in spring, and the delay in the initial period; summer rainfall is heavy and the incidence is heavy. In the apple cultivar, the onset was heavy with the Marshal and the Fuji disease was light. In addition, the tree vigor is weak, air and light transmission is poor, the terrain is low, the groundwater level is high, and the branches and leaves are tender and susceptible.
4. Control methods
1 The prevention and control of agriculture is the basis for the prevention and treatment of pressure bases in winter and spring. Thoroughly clearing the garden, burning the fallen leaves, and reducing pathogens that cause overwintering are an effective measure to prevent and treat spotted leaf disease. Many farmers tend to ignore this link, which is an important cause of the serious disease in recent years.
2 Open branch angles, pruning and trimming, improve ventilation and light transmission conditions, strengthen fertilizer and water management, and increase tree disease resistance. Pay attention to summer drainage and reduce the incidence of conditions.
3 Pharmacy prevention and control implement a comprehensive prevention, focus on governance, governance point protection. On the basis of general defense, the “reconstruction and treatment†shall be implemented in the re-emerging areas to prevent the disease from spreading, spreading, and slowing down the disease so that the disease will be eliminated early in the spotting stage. In the middle and early spring of June, the growth period of spring shoots will be 3-4 times. If there is more rain, the month should be sprayed one time; in the middle and late July, the shoot growth period should be sprayed 3-4 times before harvesting. To prevent the recurrence of disease in the late period. The use of 4% agricultural anti-120 fruit tree special 600-800 times liquid, the drug is a bio-pharmaceutical, fruit tree fungal disease treatment effect. After testing, the control effect on apple leaf spot defoliation is significant, and concurrently cures other diseases.
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