Peach perforation

Peach perforation is the most common leaf disease in peach trees. It occurs in all peach producing areas in the world. Including bacterial perforation, mildew spot perforation and brown spot perforation. Among them, bacterial perforation is the most common and widely distributed in peach producing areas all over the country. Peach trees infected with this disease can cause a large number of perforated leaves and withered branches, seriously weaken the tree potential, affect flower bud differentiation, and cause huge losses. Three kinds of perforation diseases harm not only peach trees, but also plum, apricot, cherry and other drupe fruit trees.

[symptoms]

Bacterial perforation: harms leaves, branches and fruits. When the leaf is damaged, water-stained spots are produced on both sides of the leaf vein at the initial stage, which gradually expands into brown or purple-brown near-round disease spots, and when the yellow-green halo is wet, the back overflows yellow-white gelatinous mucus, and the disease spots dry and fall off in the later stage, forming perforations. the edge of the perforation is broken and irregular. After the disease spot falls off, it forms a perforation or part of it is connected with the leaf, and the disease spot is about 2 mm. The fruit is damaged, the disease spot is dark brown, slightly sunken, the edge is water-stained, when it is wet, the disease spot appears bacterial pus, and cracks occur when dry. The branches were damaged, forming two different disease spots: spring ulcer and summer ulcer. The spring ulcer occurred on the branches extracted last summer, the initial stage produced water-immersed brown herpes, the disease spot expanded in the later stage, the epidermis of the disease part ruptured at the end of spring, and yellow mucus flowed out, which was the source of the initial infection of the year; the summer ulcer occurred on the tender branches of the same year, with lenticels as the center, forming watery round or oval dark purple spots, and then browned, slightly sunken, dry-cracked in the later stage, and overflowed yellowish-white mucus when wet.

Mildew spot perforation: harms leaves, branches, flower buds and fruits. The disease spot on the leaf was yellowish green at first, then turned to reddish brown or brown spot, round or irregular, 2~6mm in diameter, with red halo, and finally the central part of the necrotic part fell off and perforated, and then the diseased leaf fell off. The edge of the perforation was neat and there was no necrotic tissue left. The young leaves are damaged, most of them are scorched and do not form perforation. When the humidity is high, gray mildew grows on the back of the disease spot, that is, the pathogen conidiophores and conidia, and some delay to produce after shedding. When the shoot is damaged, a long ellipse disease spot is formed with the bud as the center, the edge is purple-brown, and cracks and glue flow occur. The damage to the fruit formed a disease spot with purple, gradual brown, red edge and central depression.

Brown spot perforation: harms leaves, shoots and fruits. There are round or nearly round disease spots on both sides of the leaf, with purple or reddish brown slightly ringed on the edge, with a size of 1mm to 4mm; in the later stage, grayish brown mildew appears on the disease spot, and the middle part dries off, forming a perforation, the edge of the perforation is neat, and there is often a circle of necrotic tissue outside the perforation. Brown, sunken, marginal, reddish-brown disease spots are formed on the new shoots and fruits, and the gray mildew in the shoot is dried.

[pathogen]

Bacterial perforation: the pathogen is pathogenic type Xanthomonaspruni (Smith) Dowson. The cell is short rod-shaped. Size 1.4~1.8um*0.40.8um. Solitary or connected into a short chain. There are 1-6 flagella at one end, with capsule and no spores. Gram staining is negative and aggressive. On the meat juice Agar medium, the colony is yellow, round, smooth and neatly edged; liquefied gelatin, condensed milk. The suitable temperature for development is 25 degrees.

Mildew spot perforation: the pathogen is Clasterosporiumcarpophilum (L é v.) Aderh.,. Conidiophores tufted, septate. Conidia clavate or fusiform, 3-6 segments, slightly curved, colorless or light brown, 30~56um × 6~7um in size.

Brown spot perforation: the pathogen is Pseudocercospora Pseudocercosporacircumscissa (Sacc) Liu&Guo, belonging to the genus Pseudocercospora. The common synonym is CercosporacircumscissaSacc. Conidiophores tufted, unbranched, straight or slightly curved, olive. There are 2 diaphragms, the size of 6.5~35.0um × 2.5~4.0um. Conidia slender, whip-shaped or obclavate, straight or slightly curved, light bluish yellow, 3 × 9 septum, size 25.0 ~ 80.0 × 2.0 ~ 4.0um.

[disease cycle]

Bacterial perforation disease: the pathogenic bacteria overwintering in the diseased branch tissue and begin to move the following spring. Before and after flowering, the pathogen overflowed from the diseased tissue, spread by wind, rain or insects, and invaded through stomata of leaves, bud scars of branches and lenticels of fruits. The bacteria in the ulcer spot in spring died after 10 to 13 days under dry conditions. The temperature is 1928 degrees and the relative humidity is 70% and 90%. The disease generally appeared in May and was severe from July to August. The disease of strong tree was lighter and later than that of weak tree, and the latent incubation period of strong disease was up to 40 days. The orchard is seriously affected by low-lying orchard, poor drainage, poor ventilation and poor light transmission, partial application of nitrogen fertilizer and so on. The disease of early-maturing varieties was slighter than that of late-maturing varieties.

Mildew spot perforation: the pathogen overwinters with mycelium or conidia in the damaged leaves, shoots or buds. The branches or buds of peach trees are covered with a gelatinous layer, which is beneficial to the bacteria to resist low temperature. In the following year, the overwintering pathogen produced conidia, which was spread by wind and rain, first invaded from the young leaves, produced new conidia, and then invaded the shoots or fruits. The incubation period of the disease varies greatly due to different temperatures. the incubation period of leaves is generally 5-14 days, and that of branches is 11 days. Low temperature and heavy rain is conducive to the incidence of the disease, the peak of disease in a year generally occurs in the period of Rain Water.

Brown spot perforation: the pathogen overwinters as mycelia in diseased leaves or shoots, the temperature rises in the next spring, and conidia are produced after rainfall, which are transmitted by wind and rain and infect leaves, branches and fruits. Later, the conidia produced by the disease department were re-infected. The developmental temperature of the disease was 7 ℃ 37 ℃, and the optimum temperature was 5 mi 28 min. Low temperature and heavy rain are beneficial to the occurrence and epidemic of the disease.

[disease control]

1. Strengthen the cultivation and management of orchards, enhance the rational fertilization of trees, increase the application of organic fertilizer, and avoid partial application of N fertilizer; for peach orchards with high groundwater level or heavy soil viscosity, it is necessary to improve soil and drain in time; reasonable shaping and pruning, thinning dense branches, drooping branches, dragging branches, improving ventilation and light transmission conditions, reducing orchard temperature and humidity; increasing the application of organic fertilizer to avoid partial application of nitrogen fertilizer to promote tree growth and improve disease resistance. Reduce the source of bacteria during the dormant period. Combined with winter shearing, timely cutting of diseased branches, thorough removal of diseased leaves, concentrated burning or deep burial, reducing the source of overwintering bacteria.

two。 Chemical control of early spring peach trees before sprouting, spraying 4-5 degree stone sulfur mixture or 45% crystal stone sulfur mixture, 1purl 100 Bordeaux solution, 30% green Debao glue suspension, 80% pentachlorophenol sodium (spraying time is best when the weather is sunny and windless) After leaf spreading, the effective agents are 65% zinc, 50% carbendazim, 70% thiophanate, 40% chlorothalonil, zinc sulfate lime solution, 72% agricultural streptomycin and streptomycin sulfate. during the rainy season, carbendazim or mancozeb are sprayed. From May to June, 75% Chlorothalonil wettable powder was sprayed 1-2 times, or 3% Kejukang wettable powder 1000 times, which had a good effect on perforation. For bacterial perforation, agricultural streptomycin 50-100mg / L is used for prevention and treatment; for fungal mildew spot perforation, 1000-fold solution of carbendazim wettable powder or 50% carbendazim wettable powder can be used for prevention and treatment of fungal mildew spot perforation. At the initial stage of the disease, spraying 65% Dysen zinc wettable powder for 2 times can treat many kinds of perforation diseases, or spraying 45% Teketol emulsion 2000 times, the effect is also good.