Performance symptoms There is no necrotic spot on the leaf margin of the cucumber, but there are chlorotic spots on the leaf flesh inside the leaf margin. With the passage of time, necrotic spots gradually expanded and increased in size. Due to varying degrees of victimization and victimization, there are differences in symptoms. Some necrotic lesions in the victim's leaves are very finely fragmented, and some of the victim's leaves are only chlorotic yellowing between the veins of the veins, but they have not yet reached the level of necrosis. If the adversity continues, this part of the leaf will be necrotic, but the leaf flesh around the big leaf veins will remain green and the leaves will gradually curl downwards, like parachutes. The symptoms of parachute-like curling often occur in patches. Cause analysis This is a kind of leaf burning caused by strong light in low temperature environment and it belongs to a physiological disease. Occurred in the late autumn and winter sunlit greenhouses and the mid-overwintering period, the annual low temperature period from November to March of the following year, generally occurs in the upper part of the greenhouse's upper and middle leaves, mostly plant damage on the south side of the blade, and only on a certain leaf The part of the blade facing southeast is seriously affected. The occurrence of this disease is mostly attributed to the cucumber varieties themselves. Some varieties are poor in low temperature resistance and are not resistant to glare. This phenomenon occurs when cultivated in the cold season. The authors found that in the same greenhouse, some varieties of leaves suffer and those with strong resistance can grow normally. In addition, some non-standard greenhouses, although the film light transmission performance is very good, but the wall is thin, the back of the roof is short and the elevation angle is small, resulting in the overall greenhouse insulation performance is poor, night temperature is low, temperature difference between day and night, especially the soil temperature is low, Under strong lighting, the leaves are easily burned. Prevention Choose a species that is resistant to adverse environmental conditions. The author once worked in the Daxing Changziying Science and Technology Demonstration Zone in Beijing and tested more than 20 varieties of protected land in the shed. None of the problems occurred. This disease is a chronic adverse physiological disease, and some vegetable farmers take temporary warming. It is often unable to solve the fundamental problems, and it is time-consuming and labor-intensive. Therefore, building a high-standard, high-performance solar greenhouse is the fundamental solution to this disease.