The pear flesh is delicious, the meat is crisp and juicy, sweet and sour, the flavor is aromatic, the nutrition is rich, and it can greatly promote human health. In addition, pears have the effect of clearing the lungs and nourishing the lungs. People who eat more pears rarely catch colds, so some scientists and doctors refer to pears as "all-round healthy fruits" or "general practitioners".
China is the hometown of pears, the planting area is very large, many fruit farmers rely on this for a living, and in ancient times, the planting area of pears in China is actually not small, many literati rioters left a lot of beautiful poems to praise pear trees, the famous poet Cen Shan wrote such a famous poem to describe the delicacy and beauty of pear blossoms: suddenly like a spring breeze in the night, thousands of trees and pear blossoms.
Pear trees can occur many pests and diseases during the planting process, and black star disease is one of the most harmful diseases in the growth process of pear trees. The factors affecting the occurrence of the disease are very complex, but if there is more rain during the growth process, it is the outbreak epidemic period of pear black star disease, and this disease does not only occur in a certain area, but occurs in various pear producing areas in China.
The occurrence of pear black star disease is widespread, the degree of harm is deep, and the prevention and control is difficult. At the slightest, it causes the pear fruit to deform and crack, cannot expand normally, loses its edible value with bitter taste, and seriously weakens the tree, resulting in a substantial reduction in production the following year. So what is hawthorn flower rot in the end, and how should it be scientifically and effectively prevented and controlled, so as to reduce the harm?
Today we will analyze the symptoms of pear black star disease, the incidence law, the onset time and the prevention and treatment methods of the four aspects for your reference and reference.
Pear black star disease can harm a variety of green and young tissues of pear trees, from the fall of flowers to the fruit before ripening.
1. Symptoms of leaf damage
It generally forms small circular or irregular spots between the main vein and the branch veins on the dorsal part of the leaf, which are pale yellow and blurred at the junction of disease and health. Black to black-brown mold is produced on the later plaques, which are the conidia and conidia of the pathogen, and then yellow-brown spots appear on the front of the leaf corresponding to the mold. When the disease is severe, multiple spots spread and spread into one piece, so that the leaves are covered by a layer of black mold and fall off early.
2. Petiole injury symptoms
After the petiole is damaged, a black oval spot will be formed, slightly concave, and a black mold layer will quickly be generated on it, which inhibits the water and nutrient transport of the leaf, resulting in early leaf shedding.
3. Symptoms of fruit damage
Fruits that occur in the early and middle stages of growth will form small yellowish-brown round spots on the surface of the fruit, and when the environment is suitable, the spots are covered with black mold. When the environmental conditions are not suitable, the green spots become "blue boils", and the disease department stops developing and spreading. With the enlargement of the fruit, the diseased part gradually sinks inward, the wood bolt cracks, and there is pink polyterus spore saprophysis on it, which will cause fruit deformity when severe, the fruit surface is uneven, the flesh of the diseased part is hardened and bitter, and the fruit is easy to fall off early.
The diseased fruit grows to the middle and late stages, in case of rainfall, the black mold layer on the fruit surface spots is easily washed away by the rain, and other bacteria are bred, resulting in pink or gray-white mold, resulting in the pear fruit being easily decayed when stored.
Onset of disease in the late growth period, the surface of the fruit produces round or nearly circular yellow-green or light brown spots, varying in size, uneven edges, generally slightly sunken in the shape of a mango, and a black mold layer below, which is relatively sparse.
If it encounters high temperature and high humidity in a short period of time after harvesting, it will accelerate the development and spread of disease spots.
4. Bud victim symptoms
The buds have more scales and hairs, and a mold layer will be produced on the surface in the later stages of the disease, and when the damage is serious, the bud scales crack and the buds die. The next spring, the new shoots grow from the base of the diseased buds form pale yellow spots with irregular shapes. Soon the surface of the diseased part will be covered with a black mold layer, which the grower calls "fog shoots" or "fog bud shoots", and later the disease part will be inwardly concave and cracked, forming ulcer spots.
5. Symptoms of neonatal victimization
In the spring, the new shoots that sprout from the sick buds are the sick shoots, and the diseased shoots are covered with black mold, called "black code". In the later stage, the cortex of the diseased part cracks and scabs, the spots gradually develop upwards, and the petiole becomes black. The diseased leaves turn from red to yellow, and finally lose water and dry up, not easy to fall off, or fall off and appear dry.
6. Inflorescence victimization symptoms
The inflorescence is damaged, forming spots at the base of the inflorescence or on the peduncle, covered with a layer of black mold, causing the inflorescence to wither and shed.
(1) Pathogens
Pear scaboids are subphylum ascoticular, constellation, nigra, asexual generation belongs to the subphylum hemiknossis, from the order Sporangia, nigra. The black mold seen in the disease department is the conidia and conidia of the pathogen, and the conidia can germinate in the temperature range of 5 to 30 ° C, the most suitable temperature is 15 ~ 20 ° C, and when it exceeds 25 ° C, it will inhibit germination. The relative humidity required for conidia germination is above 70%, the germination rate is highest when it exceeds 80%, and it is almost non-germinated below 50%.
(2) Environmental factors
1. Variety factors
There are significant differences in disease resistance between different varieties, generally Chinese pears have the most serious disease, followed by Japanese pears, and Western pears have the least disease. Duck pear, autumn white pear, yellow pear, An pear, etc. are more susceptible to disease, Laiyang pear, red pear, Yanzhou sydney pear is next, while glass pear, perfume pear is more disease resistant.
2. Climatic factors
The occurrence of the disease is closely related to the climatic conditions of the year. Early rainfall, frequent rainfall and heavy rainfall between May and July have created favorable conditions for the occurrence and epidemic of diseases, especially in the spring, which is rainy and wet, and is very prone to the occurrence and epidemic of diseases.
3. Management factors
Low-lying, poorly drained, heavy soil, depressed canopy, poor ventilation and light transmission of pear orchards, as well as weak trees are particularly susceptible to black star disease. In addition, whether the garden can be cleared in a timely and thorough manner directly determines the number of disease sources in the second year, which has a direct impact on the incidence of the disease.
Pear black star disease is a fungal disease, the pathogen mainly in conidia and hyphae in the bud disease and deciduous overwintering, the following spring after the germination of fruit trees, young shoots first infected, and form the center of onset. The disease is covered with black mold layer is the conidia, which gradually spreads to the leaves and fruits in the later stage, and the disease can occur throughout the growth period of the pear tree (April to September), of which the rainy season is the most serious in April to May and July to August. In early to mid-April, the pathogen first infected the inflorescence, new shoots and leaf clusters, forming the first peak of the disease, and after the rains in late May and the beginning of June, the pathogen quickly and heavily infected the leaves and young fruits, forming the second peak of the disease. After the weather turns cool in August, the temperature and humidity at this time are extremely conducive to the development of the disease, and a third peak of disease will be formed, which mainly harms the immediate ripe fruit and the young tissue of the autumn shoots, resulting in a large number of new disease spots. The conidia of the disease are very active, and the spores of the disease are mainly transmitted by air flow and rain.
1. Select disease-resistant varieties
When building the garden, it is necessary to select disease-resistant varieties of seedlings, select robust, disease- and pest-free seedlings for planting, and thoroughly disinfect the seedlings.
2. Do a good job in the hygiene of the pear garden
During the growing season, the new shoots of the disease are cut off in time to reduce the source of infection and prevent the spread of pathogens. After the leaves of the pear trees fall in late autumn and early winter, the fallen leaves and fruits are immediately cleaned, and the diseased branches are removed in combination with pruning, and the concentrated burning is reduced to reduce the source of disease. Before freezing, turn the surface soil of the pear orchard over once to bury the source of the disease and moisturize and keep warm, which is conducive to the robustness of the tree.
3. Scientific pruning
Rational pruning of fruit trees, appropriate fruit retention, improvement of the canopy ventilation and light transmission conditions, improve the ability of fruit trees to resist black star disease. After the pear tree grows new shoots, the fruit tree is regularly inspected, usually at an interval of about 10 days, and once the disease is found, it is immediately removed and taken out of the garden to burn or buried deeply.
4. Fertilize properly
Apply as much decomposing organic fertilizer as possible, or plant green manure to promote the healthy growth of the tree, enhance the tree potential, and improve the disease resistance of fruit trees. Avoid partial nitrogen fertilizer and increase phosphorus and potassium fertilizers. Extra-root topdressing can also be combined with spraying, such as leaf spraying of 0.3% urea or 0.3% potassium dihydrogen phosphate solution, thereby enhancing leaf disease resistance.
5. Fill with water as appropriate
Pear orchard irrigation should be appropriate, avoid flood irrigation, conditional areas can use drip irrigation to reduce the humidity of the orchard, reduce the occurrence of diseases.
6. Pharmaceutical control
The type and frequency of agents should be determined according to different growth periods and incidence.
(1) Pre-growth period (before wheat harvest, young fruit stage). This period is the key to the prevention and treatment of pear black star disease, and it is necessary to focus on inspections and strengthen prevention and control. In general, the drug needs to be sprayed 3 times in the year, that is, after the flowers fall (late April), mid-to-late May and early June; in the spring, it can be sprayed twice, that is, in mid-May and early June; in the spring, when the rain is frequent, it is necessary to spray once, that is, late April, early May, late May and early June. It is best to use a high-efficiency systemic fungicide for drug use in this period (the last 1 to 2 times can be used as a protective fungicide), of which the optional systemic fungicide has 40% Nova Emulsion 8000~10000 times liquid, 12.5% Quick-Poly Wettable Powder 2000~3000 times liquid, 40% Carbendazim wettable powder 500 times liquid; Protective fungicide has 70% Daisen manganese zinc 1500~2000 times liquid, 80% Dasheng m-45 wettable powder 800~1000 times liquid, 6% protective fungicide has 70% Daisen manganese zinc 1500~2000 times liquid, 80% Dasheng m-45 wettable powder 800 ~1000 times liquid, 6% Lebi ploughing 1000 ~ 1500 times liquid, etc.
(2) Middle growth. Generally, it is necessary to spray 2 to 3 times, that is, 1 time in late June, early to mid-July, and once in late July. In addition to the above-mentioned agents, 1:2:200 times bordeaux liquid and 500 to 600 times sterilized copper can also be used in this period.
(3) Before harvesting, it is generally necessary to spray 2 to 3 times, that is, in mid-August, late August and early September. The number of sprays depends on the specific condition, if the onset is mild or basically disease-free, it can be appropriately reduced by 1 to 2 sprays. However, a drug must be sprayed before fruit picking, and it is most suitable for high-efficiency systemic fungicides, which is not only conducive to reducing the number of overwintering fungal sources, but also conducive to reducing the incidence of rotten fruit in the process of storage and transportation.
Pear black star disease is an important disease that seriously affects the yield and economic benefits of pear trees, which will directly affect the normal growth of fruit trees and the quality and yield of fruits, so it is necessary to pay attention to them in the early stage of the disease and give timely prevention and control. It is necessary to give priority to the selection of disease-resistant varieties, clear the garden in time, reduce the number of pathogens in the garden, strengthen the management of water and fertilizer in the field, rationally plant densely, and prune scientifically.
In the pear tree growth period, growth period and harvest before the spraying of drugs, we must be targeted selection of drugs, control the amount of medication, in the first spray can be appropriate to increase a little agent, it should be noted that in the prevention and treatment of agents, must not be used many times in a row, and targeted selection of a variety of agents alternate use, so that not only can avoid the resistance of germs, but also extend the use of the agent, maintain its sterilization and disease prevention effect.
In short, in the prevention and treatment of pear black star disease, agricultural control should be the mainstay, chemical control as a supplement, the application of scientific and effective control methods, to reduce or avoid the occurrence of diseases, can bring high quality, high yield of pear fruit, bring a bumper harvest.
Text: Xiao He talks about agriculture
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