How to control common diseases at low temperature in overwintering cucumber with poor disease resistance

In winter, the growth of cucumber overwintering in greenhouse is easy to decline, the growth point shrinks or even stops growing, the disease resistance is poor, and the disease is aggravated. In addition, there are mainly haze days in North China after winter, and there is a serious lack of light and temperature in the greenhouse, which leads to bad symptoms of cucumber in greenhouse.

Cucumber flower topping

First, flower topping: flower topping, that is, cucumber topping, melon vine growth point shrinking, leaf color black and green, young melon rising, higher than the growth point, reproductive and vegetative growth is blocked at the same time. It is mostly caused by excessive fertilization at one time (especially phosphate fertilizer) or excessive spraying of pesticides. Control measures: ① rewatering the first time water, along with the water application of a small amount of feces and urine; ② spraying gibberellin at the growing point; ③ topdressing should be a small number of times.

Second, lack of melons: leaves and vines are thick black and green from top to bottom, with a diameter of 20 cm and a stem diameter of more than 1.2 cm, but the number of melons is very small. This symptom is caused by excessive application of nitrogen fertilizer and insufficient phosphorus and potassium fertilizer. Control measures: ① applied no or less nitrogen fertilizer such as ammonium nitrate, ammonium bicarbonate and urea within 20 days; ② applied ammonium dihydrogen phosphate and other compound fertilizer, applying 20 kg/ mu for the first time, and then 10-15 kg/ mu every 4-5 days; ③ opened the grass curtain early at night, lowered the temperature and shortened the light time in the daytime, and accumulated cucumbers 10 days later.

Third, melon: caused by the imbalance between nutrient supply and demand. Due to malnutrition caused by melons, to re-apply nitrogen fertilizer, small leaves thin application can promote broad leaves strong ammonium nitrate; leaves large and thin and yellow, application can make the leaves thick green ammonium bicarbonate. Disease prevention should be early, timely spraying carbendazim, gray mold net, grass mulch greenhouse film early uncover late cover, high night temperature, high respiratory consumption, insufficient nutrient accumulation. Room temperature in daylight is 24-28 ℃, do not exceed 30 ℃. At 14-18 ℃ at night. If the root melon does not grow up, it should be picked early; when the mature melon flowers begin to wilt, they should be picked. Through the above measures, the melons can be reduced and the yield can be increased.

Fourth, crisp leaves: cucumber leaves are black and green and wrinkled, with drooping leaf edges, broken with fingers, and small and few melon strips, which are caused by less application of organic base fertilizer and monotonous topdressing. Prevention and control measures: before cucumber planting, chicken manure and cow manure should be applied, chemical fertilizer and human manure should be applied alternately, and 300 times of rice vinegar should be sprayed on the leaf, such as a small amount of Yemanbao, Ludile or photosynthetic micro-fertilizer, which can improve the photosynthetic capacity of leaves.

Cucumber is overgrown.

5. Overgrowth: in case of continuous sunny weather, high temperature and high humidity after planting cucumber in greenhouse in early November, if the basal fertilizer is insufficient, the stem node of melon vine is too long (more than 8cm), the stem is too thick (diameter more than 0.8cm), the petiole is too long (more than 11 cm), the leaf is too large (diameter more than 14 cm), and the angle between petiole and stem is less than 45 °. The leaf stem is yellowish, the leaf is too thick and fat, the growth point is protruding, the tendrils are slender and white, and the vegetative growth is too prosperous; it is easy to occur, reproductive growth is inhibited, young melons are reduced, and do not expand. Control measures: ① reduced night temperature, the night temperature in the greenhouse gradually decreased from more than 12 ℃ to 5-6 ℃, low temperature seedling cultivation for 5-6 days, and then recovered to about 12 ℃; ② stopped watering, trapped seedlings to promote melon growth, and then watered after 60% of the young melons were enlarged, preferably less watering; ③ increased daytime ventilation, increased light transmittance, reduced leaf vine water content, and proper water loss could make the fiber stronger; ④ spraying ethephon increased melon.

Sixth, infectious diseases are common: cucumbers are easy to be infected with blight and scab due to low temperature and low light from December to February of the following year, and are susceptible to gray mold and bacterial angular spot in the middle stage of high temperature and humidity. Prevention and control measures: ① moisture control and heat preservation, keep the greenhouse dry; ② chemical control, 70% agricultural streptomycin or medical streptomycin, Kesha, pyrimidine, ethyl phosphorus, aluminum manganese zinc, Fuxing, Sukeling smoke agent, etc., comprehensive prevention and control of angular spot, blight, scab, with good results.