symptom
Pear dry rot has become an important disease in pear planting areas in northern China. It mainly harms branches and fruits. After infection, the cortex turns brown and slightly depressed, and then the diseased branches die, with dark brown particles, that is, conidia of pathogenic bacteria. The trunk was infected with the disease, and the primary annular ulcer spot, after a week of annular drying, led to the death of the above-ground part. When the fruit is infected, ring spots appear on the diseased fruit, and their symptoms are similar to those of pear ring spots, so it is necessary to identify the pathogen to distinguish them. Infected seedlings and young trees, the bark is dark brown, long and slightly wet, causing leaves to wither and branches to die. In the later stage, the affected part is dehydrated and sunken, with cracks around it and dense black spots on the surface.
cause of a disease
Botryosphaeria berengeriana de not.f.sp. piricola (nose) koganezawa et Sakuma is called dry rot fungus and belongs to Ascomycetes subfamily. Ascomycetes are medium to large. Ascomycetes are embedded in subgenus under bark, including ascomycetes and conidia. Ascomycetes have septa, oval or ovoid, large and colorless, occasionally brown, and the size is 15-28×6- 12 micron. Pseudocapsules are solitary, laterally fused or buried in the fruits of subgenus cushion. Conidia are unicellular, colorless and oval, with the size of 12-30×4-8 microns. Causing pears to dry and rot. The optimum temperature for the development of pathogenic bacteria is 25-30℃, the highest is 37℃, and the lowest is 8℃.
Transmission route and onset conditions
Pathogenic bacteria overwinter in diseased tissues as conidia, conidia or hyphae, and the spores of pathogenic bacteria spread through rain in the following year. This disease was not taken seriously in China before, but it has occurred frequently in recent years. In the past, fruits caused by dry rot were often mistaken for ring rot fruits. Poor cultivation management, insufficient fertilizer and water, weak trees and serious diseases in production. In addition, the disease is easily induced by insufficient light in the middle and lower branches of densely planted pear orchards. The branches or fruits of Yali pear, Guangli pear, Jing Pak Lei pear and Zimu pear are all infected with this disease.
Prevention and cure method
(1) Select disease-resistant varieties according to local conditions. The western pear system was seriously affected, as were Dangshan crisp pear, yellow pear and apple pear. Yali pear and Pak Lei are generally mild.
(2) Strengthening cultivation management, doing everything possible to enhance tree vigor, preventing freezing injury and improving disease resistance are the fundamental ways to prevent rot. Pear orchards should be intercropped reasonably, applied with base fertilizer, properly topdressing, carefully pruned, properly thinned flowers and fruits, adjusted load, balanced year after year, prevented early defoliation, improved the nutritional level of trees, controlled excessive growth in the later period, and enhanced the ability of trees to resist diseases and cold. In the growing season, the dead branches, diseased branches, diseased branches, diseased fruits and sawed tissues with poor healing after pruning should be cut off in time to reduce the infection and harm of rot germs.
(3) scrape the skin again. Scrape the skin on the surface of the diseased trunk with a sharp scraper from June to August. Generally, the surface gradient of 1mm should be scraped until the white and green healthy skin is exposed. Pay attention to scrape off the diseased tissue. Carefully scrape branches and other parts with thin bark to prevent the bark from being scraped through.
(4) On the basis of scraping the diseased tissues and rough epidermis on the trunk and main branches, spray fungicides with strong permeability and long residual period to eradicate the rotting germs lurking on the bark, prevent the infection of germs and prevent the occurrence of diseases. Spraying 50-fold solution of 40% thiram wettable powder or 200-fold solution of 5% Du Baijun water solution on the trunk and the base of big branches should pay attention to prevent the leaves from being damaged by the liquid medicine, and spraying the medicine again after the fruits are picked in late autumn and early winter.
(5) In the early stage of the disease, the uterus should be cleared in time when the lesion is small. The inspection interval should be arranged according to the situation of trees and the incidence, and the focus should be on the prevention before the onset of summer and autumn and winter and spring. Be sure to scrape it clean when scraping. There is nothing rotten under the bark, only the skin can be scraped. If the lesion is deep, the xylem with diseased skin should be scraped clean. After scraping, apply the medicine, using Bomei 5- 10 stone sulfur mixture or 45% crystal stone sulfur mixture with 20 times solution, 1% copper sulfate solution, 1-2 times Pingfuling water solution, 1-5 times Yubiqing solution,1. S-92 1 antibiotic 25-30 times, 843 rehabilitation agent 60-200 times, 2% agricultural antibiotic 120 water agent, 40% metalaxyl copper wettable powder 100 times, 5 times of Kelexin, and 65440% copper succinate (DT) wettable. First, the washing powder is heated in water, then the diesel emulsion is poured in, cooled, and then thiram is added.
(6) Collect the scraped sick and disabled bodies, bury or burn them in a centralized way, and remove the source of the disease.
(7) In areas with strong sunshine in winter, the rotten skin scraped clean before winter should be painted with white paint. Its preparation method: 6 kg of quicklime, 65438+ 0-3 kg of salt and 20 kg of water. First, dissolve quicklime in lime milk, then add salt and enough water.
(8) Bridges or pins can be used to help restore the tree potential in the parts with large scars on the trunk and main branches.
(9) When necessary, spraying oil emulsion (acaricide): thiophanate-methyl: water = 16: 1: 800 or spraying 5% mycotoxin aqueous solution 500 times can effectively prevent pear rot.
poultry rearing
1. Ulcer symptoms: The initial lesion on the bark is oval or irregular, slightly raised, and the cortical tissue becomes loose, wet and rotten, reddish brown to dark brown. When pressed by hand, the affected part sinks slightly and overflows with reddish-brown juice. At this time, the tissue disintegrated, easily torn and smelled of distiller's grains. Subsequently, verrucous processes appeared on the surface of the lesion, gradually breaking through the epidermis, exposing small black spots with a size of about1mm. When the air was humid, pale yellow tendrils emerged from them. After that, the lesion gradually atrophied, sank and deepened, showing dark brown to black. Cracks appear at the junction of the diseased and healthy parts. Due to the formation of callus, the lesion gradually inclines around, and the lesion expands year by year, generally slowly, and rarely surrounds the whole branch. On weak trees, weak branches or frozen pears, the diseased spots can reach the xylem directly, destroy the cambium, and quickly spread around the branches, causing the branches to die. On the strong tree with strong healing ability, the diseased skin gradually tilts up or even falls off, and a new cortex is formed under the diseased skin, which naturally heals.
2. Symptoms of branch blight: It mostly occurs on the tender branches of extremely weak pear trees. The diseased parts are not waterlogged, the shape is irregular, the edge is not obvious, and it expands rapidly, quickly surrounding the whole branch, causing it to die and densely producing small black spots. The diseased trees are weakening year by year, and their growth is not good. If it is not stopped in time, the whole tree will die.
3. Fruit symptoms: Rotting bacteria occasionally invade fruits through wounds. In the early stage, the lesion was round, brown to reddish brown soft rot, and in the later stage, small black spots were scattered in the middle, which made the whole fruit rot.
cause of a disease
Environmental wine. )Fr。 , called pear black rot shell, belongs to the class Ascomycetes. The stroma is scattered and densely distributed, initially buried, and then breaks through the epidermis. The substrate has a diameter of 0.25-3 mm, and there are 4-20 endophytic ascomycetes with a diameter of 400 microns. Ascomycetes contain 4 or 8 ascospores with a size of 40-80×8- 16 micron. The spore size of ascomycetes with 4 spores is 24-36×5-8 microns, and that of ascomycetes with 8 spores is 65438 microns. The conidia are produced in the substation, and the substation 1 contains only 1 secondary conidia. The spore cavity is multilocular with 1 hole, and conidiophore is born on the wall of conidia. Conidia cells are colorless and unbranched. Sausage-like conidia are attached to it, with blunt end and colorless single cell, and the size is 4.5-4.9× 1.0- 1.2 micron. According to the report of Japanese Saito Ryo, it is considered that pear rot fungus and apple rot fungus are the same species, and their scientific name is Valsa cerato sperma (Tode ex Fries) Maire.
Transmission route and onset conditions
The pathogen overwinters on the bark, moves in warm spring in the second year, produces spores, spreads through wind and rain, and invades from the wound. In the field, the pathogen first spreads on the exfoliated tissue of bark, and when the conditions are suitable, it invades healthy tissue. The disease has one or two peaks a year, which occurs in spring and stops spreading in summer. Autumn is active again, but the harm is lighter than that in spring. It can be regarded as a cycle of rot disease from the occurrence of deciduous layer in summer to the pathological change of deciduous layer tissue, until it enters the growth period in the spring of the following year and stops in winter.
Pathogenic conditions:
(1) Soil quality: Seven cases were seriously soaked in sand, with low organic matter content.
(2) Management: Fruit trees and old trees over 78 years old are seriously ill, poorly managed and lack water and fertilizer.
(3) Branches: Lesions mostly occur in the first and second branches, which are related to freezing injury and sunburn.
(4) Variety: Baiyang pear is seriously ill, and Jinfeng has the strongest resistance, followed by Jinhua and Su Qin, and Wujiuxiang is the worst.
Prevention and control methods:
1. Prevention of strong tree disease:
(1) Reasonable burden: According to the growth status and fertilization level of the tree, determine the appropriate fruit yield, and don't overload the tree, let alone take too many measures to increase the fruit yield for short-term benefits, such as pruning and girdling. Flowers and fruits should be properly diluted, so that the results will grow and the trees will grow.
(2) Increasing water for fertilization: For the vast pear areas in the north, the common phenomenon is lack of fertilizer and water. In fertilization, we should pay attention to increasing the application of organic fertilizer, phosphorus fertilizer, potassium fertilizer and trace element fertilizer; At the same time, do not apply too much nitrogen fertilizer.
(3) Protecting leaves and promoting roots: timely control diseases and insect pests that cause early defoliation, such as scab, gray spot, black spot, brown spot, red spider, pear net stinkbug, aphid, leaf roller moth, etc. At the same time, we should pay attention to the prevention and treatment of various root diseases.
2. Avoid and protect the wound:
(1) Thoroughly control branch pests such as Gibberella, Lepidoptera and Cerambycidae. It is not only the maker of wounds, but also the carrier of carrying and spreading bacteria. It is very important to control these pests thoroughly for the vast pear areas.
(2) Prevention of freezing injury and sunburn: the sunny side of pear branches is prone to freezing injury due to the large temperature difference between day and night; If the sunny side is not covered with leaves, it is easy to die in summer due to the sun. Effective measures to prevent freezing injury are as follows: first, paint the trunk white to reduce the temperature difference between day and night; The second is to tie grass on the trunk to cover the frost. The common formula of white coating agent is quicklime 12 ~ 13 kg. Adding 2kg of the original solution of the mixture of stone and sulfur (about 20 Baume degrees), 2kg of salt and 36kg of clear water; Or 0/0 kg of quicklime/kloc, 3-4 kg of soybean milk and 40-50 kg of water. Whitening can also prevent branches from burning day by day.
(3) Protect the wound: the larger incision should be flattened, and then coated with tung oil, varnish or Tobuzin ointment and S-92 1 antibacterial agent for protection. Large lesions should be bridged and protected in time after being cured.
3. Timely treatment of disease spots:
(1) Scraping: Scrape the upturned bark and necrotic tissue before the pear tree germinates, and then apply or spray the medicine after scraping. 300 times solution of 5O% thiram wettable powder or 1 ~ 3 degree stone sulfur mixture can be sprayed.
(2) Drug treatment of the diseased spot: After scraping the diseased spot tissue, evenly mix 70% thiophanate methyl 1 and 2.5 parts of vegetable oil, or 50% carbendazim wettable powder 1 and vegetable oil 1.5 parts to smear the diseased spot. You can also apply 5 ~ 10 degree sulfur mixed solution, 20 ~ 30 times solution of S-92 1 antibiotic, 50 times solution of 40% thiram or 30% decomposed 30 times solution, 843 recovery agent stock solution, 5 times solution of wuningmycin fermentation broth, etc. To prevent scar recurrence. Exposed xylem can be coated with coal tar or antirust paint; Heal the scar on the big trunk in time and restore the tree as soon as possible. Scraped bark and diseased branches are burned centrally.
(3) Mud smearing: In spring, smearing the mud under the canopy on the diseased spot with a thickness of more than 3 cm, and then tying it tightly with plastic sheets can also inactivate the pathogenic bacteria.