Cucumber downy mildew, commonly known as black hair, fire dragons, horse races, has recently occurred everywhere, and is one of the most serious diseases that endanger the cucumbers in greenhouses. The disease is a kind of disease with strong air circulation and strong epidemic. The disease is characterized by fierceness, rapid spread, and severe disease. Within two weeks, the entire leaf can be withered and the yield is reduced by 30% to 50%, which seriously threatens the production of cucumber. We summed up a set of comprehensive prevention and control technologies for reference by farmers.
First, the symptoms
The disease mainly damages the leaves of the plants and can also harm stems, tendrils and pedicels. In the seedling stage, adult plants can be infected. At the seedling stage, chlorotic spots appeared on the cotyledons, and irregular yellow-brown lesions appeared after expansion. When the humidity was high, a gray-black mold layer was formed on the back surface. When the disease was severe, the cotyledons became yellow and dry. In the adult stage, the incidence of disease was mainly caused by the middle leaves, gradually expanding upwards and downwards. Finally, except for the top few leaflets, the whole plant was affected. In the case of leaf disease, water-soaked pale green spots appeared at the beginning and spread quickly. In 1 to 2 days, polygon-shaped water-soaked lesions appeared due to expansion and limitation of veins. Especially in the morning, the watery plague was very obvious. It retreated slightly at noon and repeated for 1 to 2 days. The blister-like lesions began to turn yellow-brown. When the humidity was high, a layer of gray and black mold appeared on the back of the lesion. When the disease is heavy, the leaves are covered with lesions and the lesions are connected to each other, causing the edges of the leaves to curl up and dry up. Finally, the leaves are yellow and die, and the leaves are easily broken.
Second, spread and infect the way
The disease is mainly transmitted by airflow, wind and rain, and people's agricultural operations. The disease is transmitted through the various orifices of the plant. Wounds, stomata, or epidermis can invade. The pathogen is transmitted from the diseased plants to healthy plants, causing disease. The occurrence of large areas.
Third, control methods
1. Agricultural control: 1 selection of disease-resistant varieties, improve plant disease resistance. Such as the No. 1 Noodle No. 1 cucumber cultivated by the Provincial Academy of Agricultural Sciences, soaked seeds, germination seedlings: 55 °C warm soup soaking, reduce the source of the disease. The use of nutritious seedling nursery, adjust seedbed temperature so that it is conducive to seedling growth. Before transplanting, it is necessary to strengthen low-temperature exercise, cultivate strong seedlings, and increase resistance to disease. 3 to strengthen the cultivation and management: the implementation of rotation dumping. Before transplanting, apply base fertilizer, increase application of phosphorus and potassium fertilizer, deep plowing and leveling the land for sorghum and mulching. Watering after planting, timely cultivating, promote root development, make plants robust. Control the humidity in the field, achieve reasonable close planting, and minimize watering in the early stage of growth. After flowering results, the amount of watering should be increased. The amount of watering should be based on the moist state of the soil, and flood irrigation should be prohibited.
2. Chemical prevention and control: 1 The smog method or dust method can be used for the protective shelter room. The smog method uses 45% of chlorothalonil smoke agent 200 g at the beginning of the disease. They are placed in 4 to 5 places in the shed, ignited with incense or cigarettes and other dark flames, closed during smoking, smoked for 1 night, and then ventilated for the next morning. , smoked once every 7 days, can be used alone, but also alternating with the dust method, spray method used. Dust method in the early days of the disease, with a duster sprinkled 5% Garnett dust agent, 1 kg per acre, every 9 to 11 days 1 time. 2 spray method, found that the central disease strain after the selection of 70% phospho manganese zinc WP 500 times, 72.2% Precike 800 times, 72% DuPont Kelu 600 ~ 700 times spray, acres of spray 60 ~ 70 liters, once every 7 to 10 days.
3. Ecological protection and protection of protected areas: The relative humidity of the night air in the shed is more than 80% to 90%. In the early morning, the ventilation openings should be opened in time to ventilate and dehumidify the air, reduce the indoor humidity, and control the disease development at a relatively low temperature. The size of the vent opening shall be limited to 10°C in the early morning temperature. After 9 o'clock, when the indoor temperature rises and accelerates, the vent is closed, the indoor temperature is quickly raised to 34°C, and it is necessary to maintain the temperature at 33°C-34°C as much as possible to control the occurrence of the disease with high temperature and low indoor air humidity. Ventilation and dehumidification reduce the indoor air humidity, so that the environmental conditions are not conducive to the formation and germination of cucumber aspergillosis.
4. High-temperature stuffy shed: If the cucumber downy mildew has already occurred and has spread, it can be treated with high temperature stuffy shed, in the sunny morning of the first watering, desolate, so that the growing point of cucumber melon locust at the same height, 10 points, Close the tuyere, close the greenhouse and raise the temperature. Observe the observation temperature (distribute 2 to 3 thermometers evenly from the top outlet, lift the height at the same point as the growth point). When the temperature reaches 42°C, start recording the time, maintain 42°C to 44°C for 2 hours, and gradually ventilate. Slowly cool to 30°C. Cucumber downy mildew and sporangia can be relatively thoroughly killed, which can control the occurrence and development of diseases. The use of high-temperature stuffy shed methods to control the disease, no pesticide residues, is a pollution-free production of technical measures.
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