Prevention and control of apple deciduous apple brown spot caused by brown spot after rain

Apple brown spot

First, the occurrence characteristics of brown spot:

Apple brown spot is a fungal disease. Disporium of apple is the pathogen. High temperature and high humidity are the conditions for occurrence. It can occur at 5-30 ℃, and 20-25 ℃ is the most suitable. When the temperature is different, the incubation period of bacteria is also different, at low temperature, the incubation period is longer; at high temperature, the incubation period is shorter, and the relative humidity is more than 80%, which is more likely to occur. Apple brown spot mainly harms the leaves and leads to early defoliation of apples. It will soon be the season for the occurrence of brown spot again. I hope the majority of fruit farmers will do a good job in the prevention and control of brown spot.

Second, the problem of fallen leaves

1. Affecting flower bud differentiation: leaves are the main source of nutrients, and summer leaves mainly supply apple expansion and flower bud differentiation. Once the leaves are infected, a large number of leaves fall off, the nutrient supply is reduced, the flower bud differentiation is not full, and the flower momentum is not prosperous in the second year, which directly affects flowering and fruit setting.

2. The effect on apple: the leaves fell off a lot, and the production of nutrients could not keep up, which also had a great impact on the growth of apple in the same year. The apple decreased in size, dry matter, light weight, rough peel and dim color, which affected the commodity rate.

3. The influence on the tree potential: the apple tree in June and July is the key period for apple expansion and flower bud differentiation, such as a large number of fallen leaves, the leaves can not produce sufficient nutrients, then in the process of apple expansion and flower bud differentiation, it is necessary to consume the nutrients of the fruit tree itself, which is very disadvantageous to the recovery of tree potential and is easy to lead to rot.

Third, the cause of brown spot disease:

1. Medicine is not used in time: Brown spot generally begins to infect from the end of May to the beginning of June, so it should be prevented and treated in time before and after apple bagging.

2, the quality of the medicine is not up to the standard: many products for the prevention and control of brown spot, such as tebuconazole, fail in quality, lack of content or other reasons, so that the utilization rate is low, resulting in insufficient dosage and can not achieve the control effect; on the other hand, when spraying, the water consumption is insufficient and the spraying is not in place, especially in the inner hall of fruit trees, which leads to brown spot disease.

3. Improper fertilization: partial application of nitrogen fertilizer leads to the lack and deficiency of phosphorus and potassium fertilizer and trace element fertilizer, resulting in the excessive growth of fruit trees, the formation of "virtual fat people" and the decrease of disease resistance of apple trees.

4. Orchard management is not in place: unreasonable orchard pruning, too many branches, closed orchards, poor ventilation and light transmission; low-lying orchards, poor drainage, but also easy to lead to brown spot.

Fourth, prevention and control of brown spot:

The first is to strengthen the management of the orchard to improve the ventilation and light of the apple orchard; the second is to drain the low-lying land in time after rain to avoid stagnant water in the orchard for too long; the third is to increase the application of phosphorus and potassium fertilizer and organic fertilizer, balanced fertilization, not partial application of nitrogen fertilizer; fourth, timely chemical control. Chemical control: 430g/L tebuconazole 3000 Mel 4000 times + 70% methyl thiophanate 600 Mol 800 times. Spray should be thoughtful and meticulous, and should be evenly applied inside and outside the crown, up and down, and on both sides of the leaves. While spraying fungicides, appropriate insecticides are mixed to control Spodoptera litura, red spiders, peach heart borer and so on.