Pomelo brown phytophthora, also known as epidemic disease, is a relatively common disease in pomelo production, which seriously harms the production of pomelo. The disease occurs during the whole growth period of the pomelo fruit, from the young fruit stage to the mature stage. The disease is likely to occur, with serious losses of up to 10% or more. The epidemic of pomelo is closely related to climatic conditions. In the high-temperature and rainy season of May to June and 2-3 days after the typhoon rains from August to September, the orchard should actively prevent and treat the disease.
I. Symptoms of Phytophthora infestans The disease can occur in any part of the surface of the pomelo fruit. In the case of the whole tree, it occurs in the middle and lower parts of the pomelo fruit. At the beginning of the disease, there appeared a light brown dot on the peel. The small dot quickly expanded and showed a dark brown water stain. The lesion site became soft and slightly sunken. The obvious feature of the disease is the roundness of the diseased part, and a large number of fruit drops after the disease. Under the environment of high temperature and high humidity, the surface of the fruit can produce sparse pure white hyphae, and the diseased fruit emits a pungent odor.
Second, the incidence of disease and characteristics of the disease The source of infection of the disease is mainly from the soil, zoospore produced by the bacteria or zoospores released from the sporangia, by splashing rain, attached to the crown of the lower fruit, spore germination After the invasion can directly cause the incidence of fruit. The pathogenesis of the disease has the following aspects.
1. The epidemic has a clear episode in the field. The disease usually occurs in low-lying areas and in areas with high humidity. Most of them are concentrated on the canopy about 1 meter from the ground, and then spread to the surrounding areas. Fruits that are closer to the ground are more likely to become infected, and diseases that develop rapidly between fruits are more likely to develop. Two or more lesions may appear on the same fruit under optimum temperature and humidity conditions.
2. The epidemic is closely related to the climatic conditions. In the May-June months of high temperature and rainy season and August-September typhoon 2-3 days after the rain easily. Diseases spread rapidly when the temperature is between 29-31°C and relative humidity above 85%.
3. The epidemic is easy to be affected in shady orchards with poor ventilation and light transmission. Orchards, low-lying orchards, orchard lands in sand dams and flat land orchards are more prevalent than the mountain orchards, and epidemic diseases are more likely to occur in partial application of nitrogenous orchards.
4. There are significant differences in the occurrence of epidemics among different breeds. ? Ximi pomelo is most susceptible, followed by Shatian pomelo, pomelo, crystal grapefruit and so on.
Third, the prevention and control of epidemic diseases Due to the epidemic of the epidemic disease is quite rapid, once the disease causes serious losses, the prevention and control of the epidemic should be the focus. According to Meixian fruit growers in the management practice for many years to sum up the more effective measures to prevent and cure diseases, are summarized as follows:
1. Strengthen fitness training. The combination of nitrogen, phosphorus, potassium and Other trace elements on fertilization promotes strong tree vigor and does not use nitrogen fertilizer. It is best not to use ammonia bicarbonate, which can effectively reduce the occurrence of epidemics.
2, reasonable pruning, take the necessary open skylight, sparse and other measures to improve the orchard's ventilation and light transmission capabilities. The fruitless shading and drooping branches are trimmed moderately on the lower layer, and the supporting and hanging fruit techniques are applied on the lower layer.
3. Lay lime on the ground in the peak of the epidemic in April and May and use 30-50 kilograms of mu to kill surface bacteria and reduce the source of the disease.
4, pharmaceutical control. Because the disease has a short incubation period and a rapid onset of disease, it is necessary to choose the appropriate agent in time. Generally, it is used in high temperature and rainy season or after typhoon rain.
11:1:100 of Bordeaux mixture; 253% of Ledomil WP; 700-800 times; 372% of Defender Cream 600-800 times; 480% of Dasheng M-45 WP; 500-600 times; 580% of Infectious Cream Spirit 800 times and so on.
When spraying, the focus is on the inner and middle parts of the fruit trees. The diseased fruit trees can be used on the ground at the same time. The medicine can be applied once every 5-7 days. The effect is better.
I. Symptoms of Phytophthora infestans The disease can occur in any part of the surface of the pomelo fruit. In the case of the whole tree, it occurs in the middle and lower parts of the pomelo fruit. At the beginning of the disease, there appeared a light brown dot on the peel. The small dot quickly expanded and showed a dark brown water stain. The lesion site became soft and slightly sunken. The obvious feature of the disease is the roundness of the diseased part, and a large number of fruit drops after the disease. Under the environment of high temperature and high humidity, the surface of the fruit can produce sparse pure white hyphae, and the diseased fruit emits a pungent odor.
Second, the incidence of disease and characteristics of the disease The source of infection of the disease is mainly from the soil, zoospore produced by the bacteria or zoospores released from the sporangia, by splashing rain, attached to the crown of the lower fruit, spore germination After the invasion can directly cause the incidence of fruit. The pathogenesis of the disease has the following aspects.
1. The epidemic has a clear episode in the field. The disease usually occurs in low-lying areas and in areas with high humidity. Most of them are concentrated on the canopy about 1 meter from the ground, and then spread to the surrounding areas. Fruits that are closer to the ground are more likely to become infected, and diseases that develop rapidly between fruits are more likely to develop. Two or more lesions may appear on the same fruit under optimum temperature and humidity conditions.
2. The epidemic is closely related to the climatic conditions. In the May-June months of high temperature and rainy season and August-September typhoon 2-3 days after the rain easily. Diseases spread rapidly when the temperature is between 29-31°C and relative humidity above 85%.
3. The epidemic is easy to be affected in shady orchards with poor ventilation and light transmission. Orchards, low-lying orchards, orchard lands in sand dams and flat land orchards are more prevalent than the mountain orchards, and epidemic diseases are more likely to occur in partial application of nitrogenous orchards.
4. There are significant differences in the occurrence of epidemics among different breeds. ? Ximi pomelo is most susceptible, followed by Shatian pomelo, pomelo, crystal grapefruit and so on.
Third, the prevention and control of epidemic diseases Due to the epidemic of the epidemic disease is quite rapid, once the disease causes serious losses, the prevention and control of the epidemic should be the focus. According to Meixian fruit growers in the management practice for many years to sum up the more effective measures to prevent and cure diseases, are summarized as follows:
1. Strengthen fitness training. The combination of nitrogen, phosphorus, potassium and Other trace elements on fertilization promotes strong tree vigor and does not use nitrogen fertilizer. It is best not to use ammonia bicarbonate, which can effectively reduce the occurrence of epidemics.
2, reasonable pruning, take the necessary open skylight, sparse and other measures to improve the orchard's ventilation and light transmission capabilities. The fruitless shading and drooping branches are trimmed moderately on the lower layer, and the supporting and hanging fruit techniques are applied on the lower layer.
3. Lay lime on the ground in the peak of the epidemic in April and May and use 30-50 kilograms of mu to kill surface bacteria and reduce the source of the disease.
4, pharmaceutical control. Because the disease has a short incubation period and a rapid onset of disease, it is necessary to choose the appropriate agent in time. Generally, it is used in high temperature and rainy season or after typhoon rain.
11:1:100 of Bordeaux mixture; 253% of Ledomil WP; 700-800 times; 372% of Defender Cream 600-800 times; 480% of Dasheng M-45 WP; 500-600 times; 580% of Infectious Cream Spirit 800 times and so on.
When spraying, the focus is on the inner and middle parts of the fruit trees. The diseased fruit trees can be used on the ground at the same time. The medicine can be applied once every 5-7 days. The effect is better.
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