Symptom recognition and prevention of bacterial medullary necrosis in tomato
Tomato bacterial medullary necrosis is a trend of increasing the incidence of tomato in tomato growing areas in recent years, especially in facilities. The average disease rate of the diseased greenhouse is about 15%, and the serious rate is 30%-50%. If it causes a large economic loss, it should distinguish the symptoms and prevent it from being treated reasonably.
Symptom recognition. Tomato bacterial medullary necrosis mainly affects stems and branches, and leaves and fruits are also affected. Symptoms often occur in the green fruit stage of tomatoes. At the beginning of the disease, the upper middle leaves of the plants lost water and wilted, and the leaves of some small leaves of some compound leaves succumbed to the lower part. Black or brown necrotic spots appear on the surface of the stem. At the same time, the stem of the stem has an adventitious root, and then appears to the dark brown plaque near the adventitious root. The length of the lesion varies from 5 to 10 cm, and the cortex is hard. In the longitudinal direction of the diseased stem, the pathological lesion of the tomato plant can be seen. The lesion is more brown than the outer surface of the stem, and it is brown to dark brown. The medulla is necrotic at the external browning of the stem, and the shrinkage is hollow and gradually extends upwards and downwards. When the lower stem is infected, it often causes the whole plant to die. When the humidity is high, from the diseased stem wound and the petiole detachment, the adventitious root will overflow the yellow-brown pus, which can be distinguished from the ulcer disease of tomato. Tomato ulcer disease is also a bacterial disease. Once the rate of diseased plants is high, the plants often cause wilting and necrosis of the plants, and 100% of the diseases occur in severe cases. The fruit is affected by the disease, and the disease is extended to the fruit stalk, which can be extended to the fruit, causing the young fruit to shrink, dilute, deform, and seed. The surface of the tomato ulcer disease has a white round spot on the fruit surface. There is a dark brown spot in the middle of the spot, which is like the shape of a "chicken eye", which is a typical feature of tomato ulcer disease.
The law of onset. The bacterial medullary necrosis of tomato is caused by the infection of Pseudomonas sinensis. It can occur on shed or open field cultivation of tomato. The shed planting is earlier than the open field, and the course of disease develops slowly, from the performance of wilting to the death of the whole plant. About 20 days or so, the pathogens mainly invade from the pruning wounds, and spread through rainwater, farming operations, etc., which are prone to disease under low temperature and high humidity conditions, and the fields of continuous cropping, poor drainage, and excessive nitrogen fertilizer are seriously affected. In greenhouse cultivation of tomatoes, a large amount of chemical fertilizer is generally applied. In particular, the amount of nitrogen fertilizer is large. Under low temperature conditions, if the agricultural operation conditions such as pruning and snoring on a rainy day, a large number of wounds will be caused, which provides favorable conditions for the occurrence of the disease. Caused the disease to occur in the shed indoors.
Prevention. Tomato bacterial medullary necrosis is a new disease that has occurred in recent years. It is difficult to cure after onset. Therefore, comprehensive prevention and control measures should be taken in production. Agricultural control: 1. Rotation can be carried out for 2-3 years with non-solanaceae vegetables. If conditions permit, substrate cultivation can be used to fundamentally solve the problem of continuous cropping. 2. Rational fertilization. Fully apply the decomposed organic fertilizer, apply the nitrogen fertilizer without partial or excessive application, increase the application of phosphorus and potassium fertilizer, and improve the disease resistance of the plant. Conditional fertilization can be applied in combination with the application of biological bacterial fertilizer to increase the number of beneficial microbial flora in the soil to improve the soil microenvironment. 3. Reasonable cultivation. Covering with high ridge mulching is good for disease prevention; avoid watering in rainy days, timely ventilation after watering, and conditional drip irrigation can be used to avoid excessive humidity in the shed, which is conducive to disease control and timely elimination of field accumulation after rain. water. Do not pruning in the rainy days, puncture and smear on the wound in time to prevent the invasion of germs. When a diseased plant appears in the field, it should be removed in time and taken out of the field for deep burial or burning. The diseased hole can be thoroughly disinfected and sterilized with lime. At this time, watering cannot be done to prevent the spread of germs with water. Pay attention to controlling the temperature inside the shed and keep it. The night temperature in the shed is not lower than 10 °C, creating environmental conditions that are not conducive to the growth of the bacteria. Chemical control: use 72% agricultural streptomycin sulfate soluble powder 3000-4000 times liquid, or kill 77% copper hydroxide wettable powder 500 times liquid, or 50% succinic acid copper acid wettable powder 500 times liquid, Or 14% solution of lycopene copper water 300 times, spray once every 10 days, continuous control 2-3 times. It can also be used with 20% copper acetate wettable powder 2-2.8 kg plus 25% nail cream per acre. Propionate WP WP 500-700 g is applied with water. In the small-scale onset, the use of tetracycline, mesomycin and other injectable stems can also have a good control effect.
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