Pear scab is a common fungal disease in the growth and development of pear trees, which can pose a serious threat to the yield and quality of pear trees.
It is of great significance to grasp the pathogenesis, identification and diagnosis methods, pathogenesis and efficient prevention and control strategies of pear scab in the field, which is of great significance for the healthy growth and yield improvement of pear trees.
Picture 01~02): Scab disease is on the petiole of the fruit peduncle
In this issue, Qingjiang Crane will continue to pay attention to and chat with all the teachers about the related topics of pear scab, aiming to focus on the field symptom identification of pear scab, explore the incidence law, and elaborate on the prevention and control knowledge of pear scab. I hope you like and actively participate in the interactive comments, forward and share the pictures and texts of this issue.
Identification and diagnosis of pear scab disease in the field:
The onset of pear scab in the field is not unfamiliar to most fruit farmers, and they will basically identify and diagnose it. I am afraid that only a small number of people (growers or beginners who do not like to focus on various pear diseases) will not recognize or identify the symptoms of pear scab in the field or do not recognize it accurately. For the sake of "thoroughness", here is a brief overview of the symptoms of pear scab in the field.
Picture 03~04): Pear scab disease is applied to young fruits
The onset time of pear scab disease in the field is relatively long, so to speak, from the pear tree after the flowers and leaves to the pear fruit is close to maturity, as long as the disease conditions are "ripe", the disease can basically be immediately affected in the field. The onset conditions are "high temperature and high humidity". The center of the disease starts from the "diseased shoots" of the pear sprouts.
Pear scab can damage the growth and development of pear scales, buds, leaf petioles, new shoots, flowers, and fruits. The initial symptoms of pear scab are mainly small spots on the leaves that appear pale yellow (faded macula), and as the disease progresses, these spots gradually expand and turn black, and form stellate radiation lesions, which are covered with a layer of "black mold" when the air humidity is high. When the damage is serious, the leaves are scorched and fall off early.
After the fruit is damaged, black lesions appear on the surface (sometimes covered by black mold), the flesh around the lesions hardens to form scab-like depression spots, often forming "cracked fruits", radial black dots are common on the lesions, and the cracked fruit wounds become various pathogenic bacteria, infecting the "channel" of the plant, which can cause partial or total decay of the affected fruit, seriously affecting the quality and yield of the fruit.
Picture 05~06): Healthy and developed pear fruit
Leaf and young fruit disease is the most intuitive growth and development site for us to check the incidence of pear scab in the field on a daily basis. The second is the susceptibility of pear shoots, which can make the branches "crack" into a coarse skin-like scab. Therefore, pear scab is also known as "pear scab" disease.
"Precise" identification and diagnosis methods for pear scab:
The identification and diagnosis of pear scab disease is mainly based on its typical symptoms. During field inspection, fruit farmers should pay attention to the characteristics of disease spots on leaves and fruits, especially the stallate spots and black mold layer on leaves and young fruits.
At the same time, combined with the onset time of pear trees in the field (in the area of 900m~1100m above sea level, the onset time is from mid to late May to early June, and the "incubation period" of pear scab is in mid to early May, and the present symptom period on pear trees is later than that of pear rust. and environmental conditions. If in doubt, laboratory testing can be used to confirm the pathogen.
Picture 07~08): Symptoms of pear scab
Exploration of the pathogenesis of pear scab disease in the field:
The incidence of pear scab in the field is closely related to the influence of climate, cultivation management and other factors.
Generally speaking, the environment of high temperature and humidity is conducive to the reproduction and spread of pear scab pathogens, so spring and summer are the high incidence periods of pear scab.
After the pathogenic bacteria (fungi) of pear scab are safely protected on pear trees and pear orchard residues (warm winter is not conducive to the inhibition of scab pathogens in pear trees), the following spring rises with the temperature and spreads on pear trees with natural rainwater and watering.
"Diseased shoots" and "spring shoots" are the first places where overwintering pathogens are infected, and then the pathogenic bacteria that invade the plant will enter the "incubation period" (the incubation period is about 20~25 days), until the pear rust is "present" on the tree, and the symptoms of pear scab disease will "follow".
Picture 09~10): Symptoms of pear scab disease on leaves
Spring rain is the basis of the disease, and temperature is the key to the disease. As long as there is enough "rain", the spores of the germ can spread and "epidemic" when they encounter a temperature of about 22°C. The larger the pathogen base of the orchard, the more "capricious" the weather, and the more serious the disease of pear varieties with poor resistance to scab. Early or delayed medication, insufficient concentration or rain after the use of medicine, the tree type is closed and opaque, the faster and more serious the onset of pear scab.
In addition, orchards with weakened trees, poor management, and low-lying terrain that are not easily drained are also more susceptible to pear scab.
Therefore, strengthening orchard management and improving the comprehensive resistance of pear trees are important measures to prevent pear scab.
Strategies for effective prevention and control of pear scab:
According to the pathogenesis and regularity of pear scab, we can adopt the following efficient and comprehensive prevention and control strategies:
Picture 11~12): Symptoms of pear scab on petioles
First of all, it is fundamental to strengthen the management of soil, fertilizer and water in orchards, reasonable fertilization and pruning, reasonable loading, and maintain the vigorous growth and development of trees.
It is recommended to apply nitrogen, phosphorus and potassium fertilizers reasonably according to the fertilizer and water conditions of the orchard soil, and supplement medium and trace elements (some plots lack zinc or iron, and general plots do not lack phosphorus and calcium).
Secondly, varieties with strong disease resistance are selected for cultivation. For example, the new high pear is more resistant to disease than the golden pear in the second high mountain. The newly cultivated Qiuyue pear and Cuiguan pear, in the Ergao Mountain, the Cuiguan pear is more resistant to disease than the Qiuyue pear. Among the old varieties of pear trees, Shonan Chojuro is more resistant to disease than Huanghua pear. Thirdly, spray fungicides in time at the early stage of the disease for prevention and control, and pay attention to the rotation of pesticides to avoid the development of antimicrobial resistance.
Picture 13~14): pyraclostrobin is used for pear scab
The commonly used agents and concentrations of pear scab are: 20% syringoxystrobin suspension 2000 times, 50% pyroxystrobin water dispersible granules 3000 times, 22.5% pyroxystrobin suspension 1500~2000 times, 15% pyraclostrobin microemulsion 1000~1500 times liquid spray, or 25% pyraclostrobin aqueous emulsion 2000 times, 35% azoxystrobin suspension 1200~1500 times liquid spray, or 30% pyrimecothrobin suspension 800~1000 times liquid, 50% pyriconazole aqueous dispersible granules 800~1000 times liquid, 25% fluconazole suspension 2000~2500 times liquid, 50% fluconazole suspension 4000 times liquid, 30% fluconazole wettable powder 3000 times liquid, 40% fluorosilicone emulsifiable concentrate 8000~10000 times liquid spray stem and leaf treatment.
Finally, diseased leaves, fruits and other diseased residues in the field should be removed in time to reduce the source of transmission of pathogens.
Picture 15~16): Mycloconazole is used for scab in pear trees
Precautions for the prevention and control of pear scab:
In the process of prevention and control of pear scab, the following points need to be noted: First, the selection and use of pesticides should be scientific and reasonable. It is necessary not only to reduce the amount effectively, but also to avoid environmental pollution and pesticide residues caused by excessive use.
The second is to regularly inspect the orchard to find and deal with the diseased plants in the center in a timely manner. After the pear leaves are developed, different pests and diseases will occur in different growth periods of the pear tree. According to the growth and development law of pear trees in the field, we should choose the "right way" and "right symptomatic" agents in time to carry out comprehensive prevention and control of diseases and pests.
The third is to do a good job in the pruning of pear trees in the growing season, strengthen the ventilation and light transmission of the orchard, build a good high-quality, high-yield and stable yield of the tree-type inter-frame structure, reduce the humidity of the orchard, enhance the ventilation and light transmission conditions between the plants, and "create" an environment that is not conducive to the growth and reproduction of various pathogenic bacteria, and reduce the probability of disease.
Picture 17~18): Different pear tree varieties have different resistance to pear scab
Fourth, do a good job of cleaning the orchard to reduce the transmission of germs. In particular, all kinds of "sick and disabled bodies" should be taken out of the park and dealt with in a centralized manner. Work reasonably in accordance with the agricultural operation procedures, as far as possible not to "create" artificial wounds for trees in the field, and provide "convenience" for various pathogenic bacteria to invade plants.
Words written at the end of the prevention and control of "pear scab disease":
Pear scab is a major problem in pear tree production, but we can effectively prevent and control the occurrence of this fungal disease by understanding its symptoms, identification and diagnosis methods, pathogenesis and efficient prevention and control strategies.
At the same time, pay attention to the details and precautions in the prevention and control process to ensure the smooth progress of the prevention and control work. Only in this way can we ensure the healthy growth and development of pear trees, as well as high yield and high quality, and bring better economic benefits to fruit farmers.
In addition, there is an article about pear scab disease in the early pictures and texts of Qingjiang Crane, and interested friends can climb the stairs to read:
Picture 19~20): Young pear fruit without pear scab
01) How to use the "incubation period" of "pear scab disease"? These special agents can be accurately prevented and controlled once
02) After the pear blossoms, what kind of medicine can be used for the first time to comprehensively prevent and control various diseases?
03) Many pear orchards have been "hit", and the worrying pear scab is finally coming, try these special agents
04) How to prevent and control pear scabs that "can't be stopped"? There are 4 "key information" to master
05) Pear scab disease is very harmful, and it is difficult to curb the spread and expansion of seasonal prevention, so it is fundamental to do comprehensive prevention and control
06) Who is the "nemesis" of pear scab? fluconazole fluconazole or flusilazole
Picture 21~22): The pear is of high quality and high yield