In recent years, as the Virgo fruit has become more and more popular among consumers, the fruit industry has developed rapidly. However, with the increase in the area of ​​heavy sputum, the disease has become more and more serious, and some growers have suffered heavy losses. According to the investigation, the main diseases of the female fruit are early blight, late blight, leaf mold, gray mold and bacterial wilt.
First, early blight
Symptoms: In the seedling stage and adult stage, the disease can be affected, mainly affecting leaves, stems, flowers and fruits. In the early stage of the diseased spot on the leaf, it is a water-stained brown spot. It is round and enlarged. It has a concentric pattern. It produces melanin when it is wet. It forms a brown oval depression on the stem. The petiole is damaged and the oval shape is produced. Spot, dark brown or black, generally do not wrap the stem, fruit occurs in the fruit pedicle, forming a brown concave plaque, with a wheel pattern, easy to cause fruit drop.
Pathogens and pathogenic conditions: the pathogen is a fungus of the genus Alternaria. The black mold on the lesion is a conidia, and the pathogen is overwintered in the field with mycelium, conidia and conidiophores along with the diseased body. Through airflow and rainwater, the bacteria are immersed in the pores and wounds, and can also penetrate directly through the epidermis. High temperature and high humidity are beneficial to the disease. The temperature is 20-25 ° C, the humidity is above 80%, or the incidence is severe when it is rainy or exposed. When planting in the open field, it will encounter the rainy season in the result period, especially in the cold season. In the rainy season, the disease will be severe, and the leaves will gradually die from bottom to top.
Control measures: 1 seed treatment. Soaking seeds with warm soup before sowing can kill the bacteria attached to the surface of the seeds. 2 When planting, use the soil and spread the medicine on the seeds to prevent it. Spraying before planting, with medicine and planting, can spray 70% mancozeb wettable powder 500 times solution, or chlorothalonil WP 500 times solution, or 1:1:150 times Bordeaux mixture for disease prevention. 3 chemical control. In the early stage of the disease, apply 25% azoxystrobin suspension 1500-2000 times solution, or 50% iprodione wettable powder 800-1200 times solution, or 80% mancozeb wettable powder 800 times solution, or more than 50% Bacterial wettable powder 500 times liquid and other rotation spray, even spray 2-3 times, spray once every 7d.
Second, late blight
Symptoms: The stems, leaves and fruits can be harmed. The seedling stage and the adult stage can be affected, and the leaves and green fruits are the most seriously damaged. In the seedling stage, the lesion spreads from the leaf to the main stem, and the petiole and stem lesions become dark brown, rot, and the plant folds. Most of the adult plants first developed from the lower leaves. In the early morning, when the dew was not dry, the leaves were soaked in water. When the sun came out, the symptoms disappeared. The next day, the leaves showed brown spots, and the white mold layer appeared on the edges. The lesions on the stem are black and spoiled, and the plants are prone to wilting or breaking. The lesions on the fruit mainly occur in the green fruit. The lesions are initially oily and dark green, with a gradual tan, and the diseased part is irregularly cloud-like. The lesions are hard and a small amount of white mold is produced when wet.
Pathogens and pathogenic conditions: the pathogen is a fungus of the genus Phytophthora. The white mold on the lesion is the pathogen sporangia and sporangia, and there are zoospores in the sac. Rainwater can splash germs from the ground onto the plants and become the central disease strain. Low temperature and high humidity are beneficial to the disease, and sporangia spread by wind and rain. Rainfall promotes the onset of this disease, so in the rainy season, there are dew drops on the leaves, and the disease is expanding rapidly. At a relative humidity of more than 95%, there are water droplets on the leaves, and at a temperature of 18-22 °C, zoospores quickly germinate and invade. If the central diseased plant is not beaten on the same day, the next day will develop one piece. If it is still cured, it will be 1-2 days in the whole field, and even destroyed.
Control measures: 1 cultivation and disease prevention. Prevention is the main factor. At present, there is no effective disease-resistant variety at home and abroad. Under the premise of using hybrid first-generation, strengthen cultivation and disease prevention. Open field cultivation should be covered with mulch as much as possible to reduce the chance of rain splashing mud on the plants. Enter the rainy season, first play 1:1:150 Bordeaux liquid prevention, because Bordeaux liquid can form a protective layer to prevent plants from growing and over-expanding. 2 chemical control. In the easy onset season, I go to the field every morning to check the line, see the leaves are water-soaked, and immediately fight drugs, no symptoms. Optional 25% azoxystrobin suspension 1500-2000 times solution, or 68% refined metalaxyl? mancozeb water dispersible granule 600 times solution, or 69% enoyl manganese zinc wettable powder 1000 times solution , or 72% frost urea manganese zinc wettable powder 500-700 times liquid and other rotation spray, even spray 2-3 times, spray once every 7d.
Third, leaf mold
Symptoms: Mainly endanger the leaves, and in severe cases also damage the stems, flowers and fruits. At the beginning of the disease, irregular or elliptical pale yellow lesions appeared on the leaves, brown fungi were formed on the back of the leaves, and the leaves were turned back to black in the later stage. Yellow spots appeared on the front of the leaves, and the leaves were curled from bottom to top. Withered yellow. On the fruit, the fruit thorns often form round black depressions, and brown mold layers appear when wet.
Pathogens and pathogenic conditions: a fungus belonging to the genus Aspergillus. The pathogens are overwintered on the diseased body by mycelium and hyphae, and conidia can also be attached to the surface layer of the seed coat. High humidity is a condition of onset, and conidia are transmitted by airflow. The conidial germination in the humid environment invades from the stomata of the leaf back, and the hyphae spread in the intercellular space, producing spores and absorbing nutrients. The pathogen can occur at 9-34 °C, the most suitable is 20-25 ° C, the relative humidity is more than 85%, and it takes about 14 days from infection to onset.
Control measures: 1 industry prevention and control: in the severely ill areas, the diseased leaves and old leaves of the lower part of the plant are removed in time, and the light disease area is pruned in time to facilitate ventilation and light transmission. 2 chemical control: in the early stage of the disease, you can choose 25% azoxystrobin suspension 1500-2000 times solution, or 70% methyl thiophanate WP 800 times solution, or 47% spring leucomycin? Wang copper WP 500- 600 times liquid, or 75% chlorothalonil wettable powder 600-800 times liquid spray, even spray 2-3 times, spray once every 7 days.
Fourth, gray mold
Symptoms: mainly in leaves and green fruits, which have a great impact on yield. The disease is serious in the green fruit period, and the leaf symptoms begin to occur from the tip of the leaf. The lesion develops inward in a “V†shape. It is initially water-soaked, light brown, large and irregular in edge, with deep and shallow wheel patterns. A small amount of gray mold, and finally died. When the fruit is damaged, most of them firstly infect the remaining flowers or stigma, bracts, and then develop to the fruit or fruit stalk, causing the peel to turn grayish white, soft rot, and the gray mold layer grows on the surface of the diseased part, and the fruits are infected with each other.
Pathogens and pathogenic conditions: The pathogen is a fungus of the genus Botrytis. The pathogens remain in the soil for wintering, or the hyphae or conidia overwinter on the diseased bodies, and the conidia spread with airflow and rain. High humidity environment (relative humidity above 90%) is very easy to onset, and the development temperature of pathogen is 20-23 °C.
Control measures: 1 selection of good varieties: the use of high-quality disease-resistant varieties is the key to tomato production. To this end, it is necessary to plant varieties with high yield, good fruit quality and strong disease resistance according to local conditions. 2 Seed disinfection: Soak seeds with 10% sodium phosphate for 20 minutes before sowing, then wash and germination. 3 Cultivate strong seedlings: Choose rice fields or field nursery beds that have not been planted for 3 years, plough to whiten and reduce the source of bacteria. Covered with fresh straw after sowing, to moisturize and prevent the soil panel knot, and remove the straw after emergence. When the seedlings grow 2 true leaves, the seedlings are carried out. At the same time, do a good job in fertilizer management in the seedling stage in order to cultivate strong seedlings. 4 Clear field hygiene: thoroughly remove and burn diseased fruits and diseased plants, and reduce the source of infection. The tomato fruit is infected by gray mold and is mainly the petals and stigma remaining on the fruit. The petals and stigma remaining on the young fruit were removed about 10 days after the tomato flowering, and the disease prevention effect was over 80%, and had no effect on the weight of the single fruit. 5 Chemical control: Before planting, use 50% speed Keling WP 1500 times solution or 50% carbendazione WP 1000 times solution to spray on the seedbed to achieve early prevention. In the early stage of the disease, use 50% cyprodinil water to disperse granule 1000 times solution, or 40% pyrimethanil suspension 800 times solution, or 50% keering WP 1500 times solution, or 50% iprodione wettability. Powder 1000 times liquid is sprayed alternately, even spray 2-3 times, spray once every 7 days.
5. Bacterial wilt
Symptoms: Infected from the seedling stage, but not onset, until the early stages of the results show symptoms. At the beginning, the leaves wilted and drooped, and then the lower leaves withered, and finally the middle part withered. At first, the diseased plant was wilting at noon, and it returned to normal at night, with rapid onset and rapid spread. The soil is dry and the temperature is high. After 2-3 days of infection, the catheter is blocked by bacteria, and it will die soon. The plants will die and the stems and leaves will still be turquoise. The epidermis at the lower end of the stem of the diseased plant is rough, and the adventitious roots of different lengths occur. The vascular bundle of the diseased stem is browned, and the stem is cut and inserted into a glass bottle with water. It can be seen that a white silk is discharged from the section of the stem cut, which is a bacterial liquid that is exuded, and is distinguished from the wilt by this feature.
Pathogens and disease conditions: caused by infection by Pseudomonas spp., is a soil-borne bacterial disease. The pathogen keeps the winter with the residue, and no host can live in the soil for 1-6 years. Suitable for slightly acidic soil, the pathogen growth temperature is 30-37 ° C, the lowest 10 ° C, 52 ° C 10 minutes to death. When the soil temperature in the ward is 20 °C, the bacteria begin to move. When the soil temperature is 25 °C and the soil moisture exceeds 25%, the peak of the disease appears. Continuous rainy days, insufficient light, the weather suddenly turns fine, and it is easy to be pandemic.
Control methods: 1 choose grafted seedlings. Tomatoes can be grafted with rootstock resistant to bacterial wilt. 2 rounds. It can be rotated with cruciferous or gramineous crops for more than 4 years, preferably with paddy fields. 3 improve the soil. Appropriate application of lime or grass ash and other alkaline fertilizers during land preparation can reduce soil acidity and make the soil micro-alkaline to inhibit the growth of pathogenic bacteria and reduce the incidence. The application of potassium fertilizer can also inhibit the reproduction of bacterial wilt; the replacement of ammonium nitrogen fertilizer with calcium nitrate also has a certain disease prevention effect. 4 Choose seedlings without disease, use sorghum to plant, drain water in time after rainfall, use drip irrigation to avoid flooding. 5 Strengthen field management. Apply more organic fertilizer or plant ash, and minimize the root damage, remove the diseased plants in time, and disinfect with quicklime. 6 pharmaceutical treatment. In the early stage of the disease, you can use 47% jiaruin WP 500 times solution, or 72% agricultural streptomycin WP 4,000 times solution, or 30% succinate copper sulphate suspension 600 times solution, or 50% spring ray Oxychloride copper wettable powder 500 times liquid irrigation, each planting solution about 0.5kg, once every 7d, once 2-3 times, can achieve good disease prevention.
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