What are the symptoms of early deciduous disease of apple? What is the scientific method of prevention and control?

Apples are grown in many places in our country, and there are many varieties. People are familiar with Red Fuji, ugly apples, green apples and so on. In the process of apple planting, defoliation disease is easy to occur if it is not managed properly in the early stage. What are the main symptoms of the disease? What is the scientific method of prevention and control?

What are the symptoms of early apple defoliation disease?

First, if the fallen leaves of apples suffering from brown spot disease, the early leaves have brown dots, and then expand into large spots, the periphery green, irregular. There are black spots in the diseased part, and the disease spot is dark brown, accompanied by dry rot and tissue necrosis on the fruit.

Second, apple spot leaf disease is mainly harmful to leaves, petioles, twigs and fruits. After the onset of the disease, there are brown round spots at first, then gradually enlarged into large disease spots, the disease spots are brown, the edges are purple-brown, and there is often a dark dot or concentric pattern in the center. When the weather is wet, dark green mildew can be seen on both sides of the disease. In the middle and later stage of the disease, the disease spot became grayish brown to gray, some irregular, and some formed perforation. Sometimes secondary infection occurs in the later stage, resulting in small black spots on the gray-and-white spot.

Third, apple rust leaves, mainly damage young leaves, petioles, shoots and young fruits and other young green tissue. The leaves first appear orange and bright dots. After expansion, the central color is dark, and many small black spots grow, overflowing transparent droplets. After that, the droplets dried, the sexual spores blackened, and the tissue of the disease thickened and swelled. Leaves abaxially grow yellowish brown from hairs, containing a large amount of brown powder. The petiole is infected and the diseased part is slightly raised in fusiform orange. The disease of the new shoot is similar to that of the petiole at the beginning, but the disease part is sunken, cracked and easy to break in the later stage.

Second, what are the scientific prevention and control methods of apple deciduous disease?

1. Fully understand the seriousness of early deciduous disease of apple

Apple brown spot mainly harms apple leaves and causes defoliation before ripening, which can cause a large number of fallen leaves from late August to early September, seriously affecting the tree potential, resulting in abnormal ripening, decreased sweetness, flavor and poor coloring of the fruit. It is estimated that the prerequisite for fruit ripening is deciduous leaves 7-10 days earlier, which can reduce the fruit grade and seriously affect the sales price of apples. A large number of fallen leaves lead to the decrease of photosynthate and nutrition accumulation, which seriously affect the morphological and physiological differentiation of flower buds, thus affecting the quality and quantity of flower buds in the coming year. In addition to harming leaves, brown spot pathogen can also harm apple fruit, producing dark brown spots around the pedicel depression. The serious occurrence of brown spot in 2018 led to the significant aggravation of fruit brown spot during storage, and the rate of diseased fruit in some cold storage was more than 30%.

two。 Appropriate prevention is the key to successful prevention and control of early defoliation disease of apple.

High temperature and rainfall are important meteorological conditions for the occurrence of early apple defoliation disease. In most years in Weibei region of Shaanxi Province, brown spot began to occur sporadically from late June to early July, which is the key period to prevent the occurrence of brown spot. In many years of Rain Water, the first onset of brown spot can be advanced to mid-June or even early June, so the time of the first medication to prevent and cure brown spot after bagging should be advanced appropriately. According to the recent meteorological conditions and the occurrence of field diseases, it is suggested that the drug control should be started from the first ten days to the middle of June.

3. Grasp the correct interval of drug application and achieve scientific and rational drug use

The incubation period of apple brown spot pathogen is 12-30 days, and the pathogen generally takes a long time from infection to disease. It is recommended to take the medicine for the first time 2 weeks after bagging, then once every 20 days, to the end of late August, 4 times. The application period can be appropriately adjusted according to the medium-term weather forecast. In the case of continuous rain, the pesticide can be sprayed before rain. If there is little rainfall, the interval of application can be extended to 25 days.

4. Select effective medicament varieties and ensure spray quality

It is suggested that tebuconazole, pyrazole, propiconazole, oxime, tebuconazole and thiamidone tebuconazole have good inhibitory effect on brown spot pathogen. Repeated use of a single agent can increase the resistance of brown spot pathogen, and it is recommended that each fungicide should be used at most twice in one growing season. Pay attention to the medication technique. Spray equipment with good atomization should be selected and sprayed evenly to avoid omission.