In the past few years, the main diseases of tomatoes in winter were early blight, late blight and leaf mold. In the last two years, due to the influence of tomato virus disease, many areas have been planted with anti-virus varieties, some varieties for some fungi and bacteria. Sexual disease resistance is low. In addition to these three diseases, tomato gray leaf spot disease is also more serious in antiviral varieties in the recent period.
First, gray leaf spot disease.
1. Symptoms: The early leaves of the disease are covered with round or irregular dark brown spots, which are water-soaked and expand along the veins to develop irregular lesions. The central part of the lesion gradually faded from gray to taupe. The lesion is slightly sunken, small and large, 2 to 4 mm in diameter, extremely thin, and easy to rupture, perforate or fall off at the later stage.
2, prevention and treatment: after the onset can be used 33.5% quinolinone 750 times solution or copper high 600 times solution mixed with 25% bromocarbonitrile 500 times solution for foliar application, 5-7 days once, for 2 to 3 times.
Second, bacterial marrow blight. Bacterial marrow blight is also called bacterial medullary necrosis, and should be controlled in the management of winter tomatoes.
1. Symptoms: It mainly occurs in the stem of the lower part of the tomato. After the onset, a large number of adventitious roots are formed on the stem. The stem can be seen to have a transparent gel in the marrow cavity, and the leaves lose water and wilting.
2, prevention and treatment: the key to bacterial diseases is the prevention in the early stage. Here, we especially remind the vegetable farmers who have changed the vegetables in the near future. After the tomato planting and slowing down the seedlings, they should use 25% copper ammonia to mix 25% metalaxyl every 7 to 10 days. ·Cream urea cyanide 500 times liquid for root irrigation, for 2 to 3 times in a row can play a preventive effect. For the diseased plants, the above agents can be injected into the stem to control the development of the disease.
For the prevention and treatment of tomato diseases in winter, it should also be noted that combined with the management of the greenhouse, the daytime temperature is controlled at 25~30°C, and the nighttime temperature is maintained at around 14°C. When the relative humidity is above 80%, it will benefit most of the diseases, so it should be ventilated in time, properly watered, and reduce the humidity in the shed. At the same time pay attention to the whole branch and fork, to avoid excessive nitrogen fertilizer, improve the disease resistance of the plant.
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