Beet brown spot disease, commonly known as leaf spot, spot disease, fire scorpion, etc., is a common and serious disease. It occurs in all sugar beet producing areas in China. Among them, in areas with high temperatures, frequent rainfall and frequent areas or irrigated areas, the incidence of sugar beet has a great impact. According to our many years of experiments and survey results, when the degree of rickets of beet brown spot is 1 grade, the sugar beet yield is reduced by 11%, the sugar content is reduced by 0.37 degrees; when the rickets are grade 2, the sugar beet yield is reduced by 15.9%, and the sugar content is reduced by 0.9 degrees; At the grade level, the yield was reduced by 28% and the sugar content was reduced by 1.47 degrees. When the rickets were grade 4, the sugar beet yield was reduced by 37.6% and the sugar content was decreased by 2.56 degrees.
Beet brown spot disease in addition to harming raw beets, it also infects seed beet, leaf beet (kent), edible beet (red beet) and fodder beet, as well as several species such as aconite, sorrel, psyllium and dandelion.
First, the symptoms of sugar beet brown spot. Beet brown spot disease infects the leaves, petioles, flower branches and bulbs of raw beets and planted plants. The symptoms of beet brown spot disease are mainly brown or purple-brown round lesions on the middle and outer leaves and petioles. The initial spots are small and gradually enlarge, with a diameter of 3-4 mm, and a purple-brown edge formed by anthocyanins around the back spots. Sometimes the color is slightly darker or less noticeable depending on the variety and environmental conditions. The center of the late lesions is grayish white mold layer, which is more obvious in humid weather. The center of the lesion is thin and easily broken. The number of lesions on each leaf is as small as a few, and more than 1,000. When the rickets are serious, the lesions are connected into pieces, and the leaves die dry. Under natural conditions, the pathogen does not infect young leaves and only infects mature leaves. Therefore, beet brown spot disease mainly occurs on the middle and outer leaves of sugar beet plants. When the environmental conditions are conducive to disease epidemics, the bacteria gradually expand from the outer layer to the inner layer. In the later stage, the leaves of rickets died and fell off. The regeneration of new leaves caused the beet roots to elongate and form roots with leaf marks, resembling pineapples. After the petiole is susceptible, brown prismatic lesions are formed. On the beet cultivation plant, the beet brown spot disease bacteria can infect flowers and make the bulbs carry bacteria in addition to the leaves and petioles.
Second, the spread and infection of the pathogen of beet brown spot disease. The pathogen of beet brown spot disease belongs to the semi-known fungus, and the hyphae are olive-colored and aggregate together to form a mycelium group. Conidia are colorless, transparent and slightly curved in the shape of a whip, usually 6-10.
The optimal temperature for the development of beet brown spot pathogen is 25-28 ° C, and stops at 37 ° C or above or below 5 ° C. The most suitable relative humidity is 98-100%, and it is best to use water droplets (rain, dew). The conidia are weakly resistant to the external environment, only 1-2 months after attachment to the bulb, and lose vitality in the compost for 2 months. It is not the main source of the disease. The mycelium mass is very strong, and it is parasitic on the bulb, the root of the root or the leaf. It can survive for more than 2 years. It is the main source of infection in the spring of the second year. These wintering pathogens produce conidia when the spring and winter conditions are appropriate in the spring, and are transmitted by rain or wind. When the conidia fall on the leaves, they will germinate when they encounter water droplets, produce germ tubes, and invade the leaf tissue through the stomata, spread and spread in the intercellular space, and form a lesion after a certain period of incubation, and then form a sub-segment Spores, so repeatedly infested, form a large number of lesions on the field plants. The occurrence and damage degree of sugar beet brown spot in each year depends on the number of repeated infections. The more the number of times, the more serious the disease and harm.
Third, the incidence of sugar beet brown spot disease. There are several conditions for the occurrence and prevalence of sugar beet brown spot:
1. There are enough wintering pathogens. The number of overwintering pathogens (hyphae) is the basis for disease expansion. In the old areas where sugar beets have been grown for many years, there are many pathogenic myceliums in the field, which are generally heavy; the newly planted areas of sugar beet are lightly affected. Replanting, licking, or planting sugar beet near the plot of the previous year, there are many pathogens in the field and surrounding, and the incidence is heavy. Seeds that are infected with brown spot disease are early onset, which increases the chance of repeated infections and aggravates the occurrence of diseases.
2. Appropriate climatic conditions. The prevalence of sugar beet brown spot depends mainly on climatic conditions. Temperature affects the length of the incubation period. When the average temperature is 19-23 ° C (the highest temperature does not exceed 29 ° C, the lowest temperature is above 13 ° C), the incubation period is the shortest, 5-8 days, if the average temperature rises or falls, or the maximum temperature rises, Lowering the minimum temperature will extend the incubation period. Rainfall directly affects the formation and dispersion of spores. Spore formation of beet brown spot disease requires more than 98% relative humidity, so only rainfall and irrigation can meet high humidity requirements. At the same time, during the rain, conidia can be dispersed and spread due to the splash of raindrops. Generally, after 15-20 days after continuous rainfall, a peak of disease spread can occur. The temperature also affects the opening of the stomata of the beet leaves, opening the portal for spore invasion.
3. Leaf age and growth of varieties and plants. The selected sugar beet varieties, namely the germplasm and the growth of the plants, are the internal causes of sugar beet infection. Different varieties of beet brown spot disease are very different. In general, foreign varieties infected with sugar beet brown spot disease have earlier onset and have serious rickets. The domestic varieties, especially the sweet-strain series, showed strong disease resistance, and the plant growth potential was strong. The seedling stage and the new leaves were basically not susceptible to disease; generally 15 pieces of true leaves were easily infected with brown spot disease.
Fourth, the method of controlling sugar beet brown spot. The occurrence and prevalence of sugar beet brown spot disease vary greatly depending on the climatic conditions and cultivation techniques of each place. Therefore, measures to control sugar beet brown spot disease should be adapted to local conditions. In the climate-dry and dry dry beet cultivation area, the incidence is relatively light and the damage is not serious. The disease-resistant varieties and corresponding agricultural technical measures are mainly adopted; in the climate warming, rainfall or irrigated cultivation area, beet brown spots The disease has an early onset, a long duration, and a serious hazard. In the prevention and treatment, comprehensive agricultural technology measures should be adopted to plant disease-resistant varieties and supplemented by chemical control.
1. Plant resistant varieties. The varieties that have been resistant to brown spots and have excellent quality and quality, such as sweet research, Shuangfeng, Jitian, zd (Chinese-German cooperative breeding), have been selected to have at least 1 higher than the common varieties. Level, increase the sugar content by 0.5 degrees, and increase the sugar production by more than 15%.
2. Implement a rotation of more than 4 years. The beet brown spot disease is mainly caused by the formation of mycelium. Therefore, the cultivation of sugar beet is early and the disease is heavy. It is required to carry out rotation for more than 4 years to reduce the amount of bacteria in the soil. When the crop is rotated, the beet must be more than 50 meters away from the beet land of the previous year, and arranged in the upper wind to reduce the spread of pathogens and rain.
3, clear the diseased leaves in the field, and implement autumn turn. When the beet is harvested, a large number of residual diseased leaves are often left in the field, which is the main source of infection of the beet brown spot pathogen in the second year. Therefore, it must be carefully cleaned up, transported out of the field, and then turned over in the autumn.
4, strengthen the forecast and forecast of sugar beet brown spot disease, timely spraying and prevention. In order to give full play to the maximum effect of chemical control, it is necessary to grasp the epidemic law of sugar beet brown spot disease, and determine the number of sugar beet sprays based on the predicted forecast results. Chemical control of sugar beet brown spot is the most effective measure. The currently available effective agents are as follows:
150% thiophanate WP 1000 times solution; 270% methyl thiophanate WP 1500-2000 times solution; 350% carbendazim WP 1000 times solution; 45% chlorothalonil WP 1000 times solution; 540% virulence (ie 20% carbendazim + 20% sulphur) suspension, 50-65 ml per acre, formulated into 600-800 times solution; 620% carbec WP 8.0 times solution.
Under the condition of no drug resistance of the beet brown spot disease, the above agent can generally maintain 10-20% of the yield and increase the sugar content by about 1 degree.
Usually, phenylpropimidazoles such as thiophanate, carbendazim and their compounding agents have been used continuously for more than 3 years. The pathogen of beet brown spot disease is resistant, even without control. It can be replaced by graben or chlorothalonil. .
Preparation method of the medicament: firstly add a small amount of water to the paste, and then fully agitate the diluted water to prepare the desired concentration of the liquid. 40-50 kg of liquid per acre. Spraying time: After the first batch of lesions appeared in the field, 5-10% of the plants started to spray for the first time, and then sprayed once every 15 days. It is best to spray the medicine when the dew is dry after 10 am. In areas or areas where the disease is mild, spray 1-2 times; if the disease is serious, spray 3-4 times. If the rain occurs within 6 hours after spraying, the spray should be supplemented as appropriate. If the damage of above-ground pests such as Spodoptera frugiperda and Spodoptera exigua occurs, it can be mixed with insecticides.
Beet brown spot disease in addition to harming raw beets, it also infects seed beet, leaf beet (kent), edible beet (red beet) and fodder beet, as well as several species such as aconite, sorrel, psyllium and dandelion.
First, the symptoms of sugar beet brown spot. Beet brown spot disease infects the leaves, petioles, flower branches and bulbs of raw beets and planted plants. The symptoms of beet brown spot disease are mainly brown or purple-brown round lesions on the middle and outer leaves and petioles. The initial spots are small and gradually enlarge, with a diameter of 3-4 mm, and a purple-brown edge formed by anthocyanins around the back spots. Sometimes the color is slightly darker or less noticeable depending on the variety and environmental conditions. The center of the late lesions is grayish white mold layer, which is more obvious in humid weather. The center of the lesion is thin and easily broken. The number of lesions on each leaf is as small as a few, and more than 1,000. When the rickets are serious, the lesions are connected into pieces, and the leaves die dry. Under natural conditions, the pathogen does not infect young leaves and only infects mature leaves. Therefore, beet brown spot disease mainly occurs on the middle and outer leaves of sugar beet plants. When the environmental conditions are conducive to disease epidemics, the bacteria gradually expand from the outer layer to the inner layer. In the later stage, the leaves of rickets died and fell off. The regeneration of new leaves caused the beet roots to elongate and form roots with leaf marks, resembling pineapples. After the petiole is susceptible, brown prismatic lesions are formed. On the beet cultivation plant, the beet brown spot disease bacteria can infect flowers and make the bulbs carry bacteria in addition to the leaves and petioles.
Second, the spread and infection of the pathogen of beet brown spot disease. The pathogen of beet brown spot disease belongs to the semi-known fungus, and the hyphae are olive-colored and aggregate together to form a mycelium group. Conidia are colorless, transparent and slightly curved in the shape of a whip, usually 6-10.
The optimal temperature for the development of beet brown spot pathogen is 25-28 ° C, and stops at 37 ° C or above or below 5 ° C. The most suitable relative humidity is 98-100%, and it is best to use water droplets (rain, dew). The conidia are weakly resistant to the external environment, only 1-2 months after attachment to the bulb, and lose vitality in the compost for 2 months. It is not the main source of the disease. The mycelium mass is very strong, and it is parasitic on the bulb, the root of the root or the leaf. It can survive for more than 2 years. It is the main source of infection in the spring of the second year. These wintering pathogens produce conidia when the spring and winter conditions are appropriate in the spring, and are transmitted by rain or wind. When the conidia fall on the leaves, they will germinate when they encounter water droplets, produce germ tubes, and invade the leaf tissue through the stomata, spread and spread in the intercellular space, and form a lesion after a certain period of incubation, and then form a sub-segment Spores, so repeatedly infested, form a large number of lesions on the field plants. The occurrence and damage degree of sugar beet brown spot in each year depends on the number of repeated infections. The more the number of times, the more serious the disease and harm.
Third, the incidence of sugar beet brown spot disease. There are several conditions for the occurrence and prevalence of sugar beet brown spot:
1. There are enough wintering pathogens. The number of overwintering pathogens (hyphae) is the basis for disease expansion. In the old areas where sugar beets have been grown for many years, there are many pathogenic myceliums in the field, which are generally heavy; the newly planted areas of sugar beet are lightly affected. Replanting, licking, or planting sugar beet near the plot of the previous year, there are many pathogens in the field and surrounding, and the incidence is heavy. Seeds that are infected with brown spot disease are early onset, which increases the chance of repeated infections and aggravates the occurrence of diseases.
2. Appropriate climatic conditions. The prevalence of sugar beet brown spot depends mainly on climatic conditions. Temperature affects the length of the incubation period. When the average temperature is 19-23 ° C (the highest temperature does not exceed 29 ° C, the lowest temperature is above 13 ° C), the incubation period is the shortest, 5-8 days, if the average temperature rises or falls, or the maximum temperature rises, Lowering the minimum temperature will extend the incubation period. Rainfall directly affects the formation and dispersion of spores. Spore formation of beet brown spot disease requires more than 98% relative humidity, so only rainfall and irrigation can meet high humidity requirements. At the same time, during the rain, conidia can be dispersed and spread due to the splash of raindrops. Generally, after 15-20 days after continuous rainfall, a peak of disease spread can occur. The temperature also affects the opening of the stomata of the beet leaves, opening the portal for spore invasion.
3. Leaf age and growth of varieties and plants. The selected sugar beet varieties, namely the germplasm and the growth of the plants, are the internal causes of sugar beet infection. Different varieties of beet brown spot disease are very different. In general, foreign varieties infected with sugar beet brown spot disease have earlier onset and have serious rickets. The domestic varieties, especially the sweet-strain series, showed strong disease resistance, and the plant growth potential was strong. The seedling stage and the new leaves were basically not susceptible to disease; generally 15 pieces of true leaves were easily infected with brown spot disease.
Fourth, the method of controlling sugar beet brown spot. The occurrence and prevalence of sugar beet brown spot disease vary greatly depending on the climatic conditions and cultivation techniques of each place. Therefore, measures to control sugar beet brown spot disease should be adapted to local conditions. In the climate-dry and dry dry beet cultivation area, the incidence is relatively light and the damage is not serious. The disease-resistant varieties and corresponding agricultural technical measures are mainly adopted; in the climate warming, rainfall or irrigated cultivation area, beet brown spots The disease has an early onset, a long duration, and a serious hazard. In the prevention and treatment, comprehensive agricultural technology measures should be adopted to plant disease-resistant varieties and supplemented by chemical control.
1. Plant resistant varieties. The varieties that have been resistant to brown spots and have excellent quality and quality, such as sweet research, Shuangfeng, Jitian, zd (Chinese-German cooperative breeding), have been selected to have at least 1 higher than the common varieties. Level, increase the sugar content by 0.5 degrees, and increase the sugar production by more than 15%.
2. Implement a rotation of more than 4 years. The beet brown spot disease is mainly caused by the formation of mycelium. Therefore, the cultivation of sugar beet is early and the disease is heavy. It is required to carry out rotation for more than 4 years to reduce the amount of bacteria in the soil. When the crop is rotated, the beet must be more than 50 meters away from the beet land of the previous year, and arranged in the upper wind to reduce the spread of pathogens and rain.
3, clear the diseased leaves in the field, and implement autumn turn. When the beet is harvested, a large number of residual diseased leaves are often left in the field, which is the main source of infection of the beet brown spot pathogen in the second year. Therefore, it must be carefully cleaned up, transported out of the field, and then turned over in the autumn.
4, strengthen the forecast and forecast of sugar beet brown spot disease, timely spraying and prevention. In order to give full play to the maximum effect of chemical control, it is necessary to grasp the epidemic law of sugar beet brown spot disease, and determine the number of sugar beet sprays based on the predicted forecast results. Chemical control of sugar beet brown spot is the most effective measure. The currently available effective agents are as follows:
150% thiophanate WP 1000 times solution; 270% methyl thiophanate WP 1500-2000 times solution; 350% carbendazim WP 1000 times solution; 45% chlorothalonil WP 1000 times solution; 540% virulence (ie 20% carbendazim + 20% sulphur) suspension, 50-65 ml per acre, formulated into 600-800 times solution; 620% carbec WP 8.0 times solution.
Under the condition of no drug resistance of the beet brown spot disease, the above agent can generally maintain 10-20% of the yield and increase the sugar content by about 1 degree.
Usually, phenylpropimidazoles such as thiophanate, carbendazim and their compounding agents have been used continuously for more than 3 years. The pathogen of beet brown spot disease is resistant, even without control. It can be replaced by graben or chlorothalonil. .
Preparation method of the medicament: firstly add a small amount of water to the paste, and then fully agitate the diluted water to prepare the desired concentration of the liquid. 40-50 kg of liquid per acre. Spraying time: After the first batch of lesions appeared in the field, 5-10% of the plants started to spray for the first time, and then sprayed once every 15 days. It is best to spray the medicine when the dew is dry after 10 am. In areas or areas where the disease is mild, spray 1-2 times; if the disease is serious, spray 3-4 times. If the rain occurs within 6 hours after spraying, the spray should be supplemented as appropriate. If the damage of above-ground pests such as Spodoptera frugiperda and Spodoptera exigua occurs, it can be mixed with insecticides.
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