How to control cucumber vine blight with leaf atrophy and disease spot

Cucumber vine blight (rotten vine), refers to the cucumber just a large number of melons, such as touching high temperature and humidity, cucumber leaves wilted during the day, recovery at night, so repeated for several days, the leaves lose function, and finally the leaves of the whole cucumber droop and cannot be recovered. With the development of the disease, the epidermis at the base of the stem was longitudinally split and there was brown glue flow. When the humidity is high, there are white or pink mildew, longitudinal section of the diseased stem, it can be seen that the vascular bundle turns brown. Within a few days, the whole ridge and the whole field will lose water and wilt, leaving obvious disease spots. The disease is a soil-borne disease. The pathogen of vine blight can survive in the soil for 5-6 years. Continuous cropping land, clayey land, low-lying land, poor drainage and extensive management will lead to cucumber vine blight.

Cucumber vine blight

Symptom recognition: cucumber leaves and stems are susceptible to disease. After the damage to the leaves, nearly round or irregular disease spots are formed, and some disease spots develop into "V" shape or semicircle from the leaf edge, light brown to yellowish brown. In the later stage, the disease spot is easy to be broken, and there are dense black spots on the disease spot. This black spot is the conidium of the pathogen. The diameter of the lesion is about 10ml 35mm, and a few of the spots are even larger. The diseased leaves were withered and yellow from top to bottom, but did not fall off. When the disease was serious, only the upper 1 Mel and 2 leaves were asymptomatic. When the petiole, melon vine and stem base are killed, the disease spot is oil-immersed, round to rhombic, yellowish brown, and sometimes there is an amber resin overflow. When the disease is serious, the stem nodes turn black and rotten, break, and the diseased parts often crack, showing yellowish brown to reddish brown after drying. The surface is dotted with small black particles.

Transmission route and disease condition: cucumber vine blight is a fungal disease, which overwinters with the remains of cucumber diseased plants in soil, seeds and scaffolding in greenhouse, and spreads through wind, rain and irrigation water. The pathogen invaded from stomata, water pores and wounds of cucumber plants. The seeds are infected with bacteria, resulting in the disease of leaves. The suitable temperature for the occurrence of vine blight is 18Mel 25 ℃, and the humidity is more than 85%, especially in continuous overcast days, where the dew is heavy at night; flood irrigation and high soil moisture are suitable for the occurrence of cucumber vine blight. In addition, continuous cropping land, flat cultivation, poor drainage, high density, lack of fertilizer, cucumber plants with weak growth are all prone to disease.

Prevention and control methods:

First, choose disease-free cucumber seeds and seeds for disinfection. Disease-free field and disease-free cucumber plants were selected as remaining seeds. If cucumber seeds are suspected of being infected, soak in 55 ℃ warm water for 15 minutes, or soak in 40% methanol solution for 30 minutes, then wash and sow.

Second, implement 2-3 years of rotation, formula fertilization, strengthen fertilizer and water management. Apply sufficient base fertilizer and increase phosphorus and potash fertilizer. The use of biological fertilizer, active organic fertilizer and inorganic compound fertilizer should be reasonable. During the growth period of cucumber, topdressing should be applied many times to prevent premature senescence and enhance disease resistance. When watering, avoid flooding, ploughing in time after watering, and properly control watering to reduce soil and air humidity after the disease. And timely ventilation and dehumidification. When diseased plants are found, they should be removed in time.

Third, disinfect the shed. Before cucumber planting, the greenhouse needs to be disinfected. 300 ml formalin and equal amount of water can fumigate 37 cubic meters of greenhouse. Fumigation for 6 hours at a time.

Fourth, chemical prevention and control. In the early stage of the disease, spraying in the whole shed can be carried out with 75% chlorothalonil wettable powder 600 times, or 65% Dysen zinc powder 500-700 times, or 50% topiramine wettable powder 500 times, or 50% carbendazim wettable powder 500 times, 5rel once every 7 days. You can also use 50% carbendazim wettable powder 500 times to irrigate the root twice. If the stem is infected, you can apply carbendazim or chlorothalonil to the diseased part of the cucumber in a paste.