Bacterial perforation of peach

[distribution] all over the country, especially in coastal areas, lakeside areas, orchards with poor drainage and rainy years, often occur seriously. If the prevention and control is not timely, it is easy to cause a large number of fallen leaves, reduce the accumulation of nutrients, and affect the formation of flower buds. It not only weakens the tree potential and reduces production in the same year, but also affects the results of the second year, resulting in a poor harvest.

[symptoms]

Small watery, yellowish spots appear on the leaves, then expand into red spots, then turn brown, the edge is darker than the center, there is a translucent yellowish halo around the edge, and the edge is easy to separate layers, forming round perforation spots, and several disease spots are linked together. the perforation shape is irregular; in severe cases, there are dozens of disease spots in a leaf, and the diseased leaf falls off early.

After the fruit is damaged, it produces oily brown dots, then the disease spot expands, the color deepens, and finally it is sunken and cracked, resulting in decay. The branches appeared watery at first, with purplish brown spots, and then sunken and cracked. When damp, white pus appears on the lesion. Cracks often occur when they are dry.

After the branches are damaged, there are two different disease spots, one is called spring ulcer, the other is summer ulcer. Spring ulcers occurred on branches that grew in the summer of the previous year (the germs had invaded the previous year). When the first batch of new leaves appear in spring, dark brown herpes are formed on the branches, about 2 mm in diameter, and then expand as long as 1 to 10 cm, with a width of no more than half of the branch diameter, sometimes causing branch blight. At the end of spring (before and after flowering), the epidermis of the disease spot ruptured, the bacteria exudated and began to spread. Ulcers occurred more frequently in summer than at the end of summer, and lenticels were the center of the shoots in the same year, forming water-stained dark purple spots. After that, the lesion turned brown to dark brown, round or oval, slightly sunken, and the edge was waterlogged. The disease spot of summer ulcer is not easy to expand, and will soon dry up, so the spread effect is not big.

[pathogen] the pathogen is bacteria, Xanthomonas campestris peach pathogenic variety (Xanthomonascampestrispv.pruni). It belongs to Xanthomonas aeruginosa, which is short rod-shaped, round at both ends, polar single flagellum, capsular, no spores. The low temperature for the growth and development of the pathogen was 3 ℃, the optimum temperature was 24 ℃ to 28 ℃, and the highest temperature was 37 ℃. If you are exposed to the sun for 30 to 45 minutes, you will lose your vitality and survive for 10 to 13 days in dry conditions. The pathogenic bacteria overwintered mainly in the diseased tissues of branches, and were spread by wind, rain and insects. With the rise of air temperature, the overwintering bacteria began to move, multiply in large numbers, overflow pus and invade from leaf stomata and lenticels of branches.

[condition of onset]

The occurrence of the disease is related to climate, tree potential, management and variety.

1. Climate: warm, Rain Water frequent or foggy, heavy foggy season, which is conducive to bacterial infection and reproduction, the disease is serious.

2. Tree potential: the disease is light and late when the tree is strong, and early and severe when the tree is weak.

3. Management: the orchard is low-lying, poor drainage, light transmission, poor ventilation, partial application of nitrogen fertilizer.

4. Varieties: the lightly susceptible varieties are Lincheng peach, Okubo, Dahe white peach, Zhongshan golden peach, Cangfang Zaosheng and canned peach 2; the moderately susceptible varieties are star, canned peach 12, Qingjian, Zhongjin white peach and golden peach; the seriously susceptible varieties are Feicheng peach, Baifeng, Baitao, Gaoyang white peach and Xiye white peach. In general, the disease of early-maturing varieties is mild, while that of late-maturing varieties is serious.

[incidence regularity] the pathogen overwintered mainly on the diseased branches, mainly in the canker spot in spring. The bacteria latent in the tissue began to move with the rise of temperature in the next spring. The bacteria exudated from the diseased tissue before and after flowering, spread by wind, rain or insects, invaded through the stomata of leaves and lenticels of branches, and the incubation period was 7-14 days. The bacteria in the ulcer spot of the branch can survive for more than one year. Ulcer spot in spring is the main source of primary infection of the disease. The summer temperature is high, the humidity is small, the ulcer spot is easy to dry, and the peripheral healthy tissue is easy to heal, so the bacteria in the ulcer spot die after 10-13 days under dry conditions. The temperature is 19 Mel 28 ℃ and the relative humidity is 70%-90%. Bacteria like warm and humid environment, Shanghai began to get sick in May, perforation can be seen in June, drought and high temperature in summer, the disease develops slowly, and late infection occurs during autumn rain. The incubation period varies with the temperature and the strength of the tree. For example, the incubation period is 4 to 5 days at 25 ℃ to 26 ℃, 9 days at 20 ℃, and 16 days at 19 ℃. If the tree is strong, the incubation period can reach 40 days, warm, rainy, foggy, and prone to serious disease when the climate is humid; there are many sprouting branches in the lower part, and the disease is serious; the disease of old trees is serious; poor management, desolation of peach orchards, poor ventilation and light transmission, weak and serious disease In addition, if there are leafhoppers, aphids, as well as poor drainage, poor ventilation, partial application of nitrogen fertilizer, will aggravate the disease. With different varieties, the degree of disease is the same. It is still harmful to plums, apricots, cherries and other plants.

[prevention and control methods]

Advocate the policy of "giving priority to prevention and comprehensive prevention", according to the principle of "early treatment, small treatment and cure".

(1) Horticultural control: emphasis should be placed on sanitary measures, such as removal of fallen leaves and withered branches in winter, and proper pruning to remove diseased branches and leaves in time. The branches and leaves should be buried deeply in time, strengthen the management of fertilizer and water, increase the application of organic fertilizer, not partial application of nitrogen fertilizer, pay attention to drainage, ventilation and light, reduce humidity, so as to enhance the tree potential.

(2) Chemical control: peach trees were sprayed with Baume 3-5 degree stone sulfur mixture before germination. Before germination, it can also be sprayed with 1RV 120 Bordeaux solution, 77% WP 300x, or 30% Lvdebao suspension 300x, spray 800x or 80x carbendazim, 70% topiramine or 70% mancozeb, 500x mancozeb, 1000 times 50x mancozeb, 1000 times 50% carbendazim once a month from May to August. Spray 65% wettable Dyson zinc 300 to 500 times from the end of May to the end of June once or twice. After flowering, spray 1V 4V 240 zinc sulfate lime solution, or 1500 times of methyl topiramate, or other fungicides. Spraying 20% Yeqing double wettable powder 600 times, or 10% Yekujing wettable powder 400 times, has a good control effect. Focus on prevention and control of plum rain and typhoon season.

(3) avoid mixed planting with stone fruit trees: in the construction of peach orchards, not only pure tree species and disease-resistant varieties should be selected, but also other stone fruit trees such as plums, apricots and cherries should not be planted nearby.