Four diseases must be a key focus for prevention and control in winter greenhouse cucumber cultivation
Winter greenhouse cucumber cultivation requires heavy prevention of four diseases
In recent years, the types of diseases in winter greenhouse cucumber cultivation have increased year by year, causing varying degrees of damage to cucumber production. Several symptoms and prevention experiences of these diseases and pests are introduced here for vegetable growers' reference.
Bacterial angular leaf spot In the early stage of the disease, it appears as fresh green water-soaked spots, gradually turning light brown. The lesions are limited by leaf veins and appear polygonal, grayish brown or yellow-brown. When humidity is high, milky white cloudy water-droplet-like bacterial ooze overflows on the underside of the leaves, and white marks remain after drying. The diseased tissue is brittle and easily perforated. On stems, petioles and fruits, the lesions are water-soaked round spots, with white mucus when moist and white after drying. Prevention and control: In the early stage of the disease, spray with 1000-fold solution of agricultural streptomycin soluble powder, or 500-fold solution of 30% DT fungicide, or 1000-fold solution of 5% chlorothalonil dust, which gives relatively high control efficacy.
Fusarium wilt The pathogen of Fusarium wilt has extremely strong vitality and can survive in soil for more than 5 years. High temperature and high humidity are favorable conditions for the occurrence of Fusarium wilt. Excessive nitrogen fertilizer and acidic soil make the disease more severe. Plots with many root-knot nematodes and plots with flood irrigation also have more severe disease. Prevention and control: In addition to selecting disease-resistant varieties, crop rotation with non-cucurbit vegetable crops for more than 3 years can be adopted to reduce the accumulation of pathogens in the soil; in the early stage of the disease, spray with 500-fold solution of 50% carbendazim wettable powder or 800-fold solution of 70% thiophanate-methyl wettable powder, or drench the roots with 1000-fold solution of 70% dexon wettable powder or 800-fold solution of 50% lilening, pouring 250 milliliters per plant, once every 7 days, for 3 consecutive times. Grafting is also a relatively ideal method for controlling cucumber Fusarium wilt. Using black-seed squash, which has a well-developed root system, tolerance to low temperature and resistance to Fusarium wilt, as the rootstock and cucumber as the scion, approach grafting or plug grafting gives excellent disease control results.
Downy mildew In the early stage of the disease, water-soaked pale yellow irregular small spots appear on the underside of leaves or leaf margins. As the disease develops, the lesions gradually expand and, limited by leaf veins, form polygonal yellow spots. When the disease is severe, small lesions merge into large lesions, and under moist conditions a gray-black mold layer grows on the underside of the lesions. Diseased leaves develop from the bottom upward, and in severe cases the leaves of the whole plant wither and die. Prevention and control: First, apply sufficient base fertilizer, appropriately increase phosphorus and potassium fertilizer, cultivate strong seedlings, water under the film, and reduce the number of waterings. Strengthen ventilation and reduce air humidity. Second, chemical control can be used, specifically 800-1000-fold solution of 25% ridomil wettable powder, 500-600-fold solution of 75% chlorothalonil wettable powder, 600-800-fold solution of 72% kelu wettable powder, or 600-1000-fold solution of 72% pulyke aqueous solution by spraying. You can also use 20-30 grams of chlorothalonil smoke agent per mu each time to fumigate the greenhouse. Apply once every 7-10 days, for 3-5 consecutive treatments.
Root-knot nematode disease The symptoms of cucumber root-knot nematode disease are mainly manifested in the roots. Mildly diseased plants show no obvious symptoms, while severely diseased plants are shorter, poorly developed, and set fruit poorly, and wilt at noon under drought conditions. When diseased cucumber vines are pulled up, root knots of varying sizes can be found on lateral roots or fibrous roots. Some appear in a bead-like series, making the root system thicker. When root knots are dissected, very small milky white root-knot nematodes can be found in the diseased tissue. Prevention and control: Methods such as deep plowing and sun-drying the soil, irrigation during idle periods, and increasing application of decomposed organic fertilizer can be used. If root-knot nematode disease occurs during cucumber growth, drench the roots with 1500-fold solution of 50% phoxim emulsifiable concentrate or 500-fold solution of 30% jiasheng microcapsule suspension emulsion, pouring 0.25-0.5 kilograms of liquid per plant; generally one drenching is enough.
Bacterial angular leaf spot In the early stage of the disease, it appears as fresh green water-soaked spots, gradually turning light brown. The lesions are limited by leaf veins and appear polygonal, grayish brown or yellow-brown. When humidity is high, milky white cloudy water-droplet-like bacterial ooze overflows on the underside of the leaves, and white marks remain after drying. The diseased tissue is brittle and easily perforated. On stems, petioles and fruits, the lesions are water-soaked round spots, with white mucus when moist and white after drying. Prevention and control: In the early stage of the disease, spray with 1000-fold solution of agricultural streptomycin soluble powder, or 500-fold solution of 30% DT fungicide, or 1000-fold solution of 5% chlorothalonil dust, which gives relatively high control efficacy.
Fusarium wilt The pathogen of Fusarium wilt has extremely strong vitality and can survive in soil for more than 5 years. High temperature and high humidity are favorable conditions for the occurrence of Fusarium wilt. Excessive nitrogen fertilizer and acidic soil make the disease more severe. Plots with many root-knot nematodes and plots with flood irrigation also have more severe disease. Prevention and control: In addition to selecting disease-resistant varieties, crop rotation with non-cucurbit vegetable crops for more than 3 years can be adopted to reduce the accumulation of pathogens in the soil; in the early stage of the disease, spray with 500-fold solution of 50% carbendazim wettable powder or 800-fold solution of 70% thiophanate-methyl wettable powder, or drench the roots with 1000-fold solution of 70% dexon wettable powder or 800-fold solution of 50% lilening, pouring 250 milliliters per plant, once every 7 days, for 3 consecutive times. Grafting is also a relatively ideal method for controlling cucumber Fusarium wilt. Using black-seed squash, which has a well-developed root system, tolerance to low temperature and resistance to Fusarium wilt, as the rootstock and cucumber as the scion, approach grafting or plug grafting gives excellent disease control results.
Downy mildew In the early stage of the disease, water-soaked pale yellow irregular small spots appear on the underside of leaves or leaf margins. As the disease develops, the lesions gradually expand and, limited by leaf veins, form polygonal yellow spots. When the disease is severe, small lesions merge into large lesions, and under moist conditions a gray-black mold layer grows on the underside of the lesions. Diseased leaves develop from the bottom upward, and in severe cases the leaves of the whole plant wither and die. Prevention and control: First, apply sufficient base fertilizer, appropriately increase phosphorus and potassium fertilizer, cultivate strong seedlings, water under the film, and reduce the number of waterings. Strengthen ventilation and reduce air humidity. Second, chemical control can be used, specifically 800-1000-fold solution of 25% ridomil wettable powder, 500-600-fold solution of 75% chlorothalonil wettable powder, 600-800-fold solution of 72% kelu wettable powder, or 600-1000-fold solution of 72% pulyke aqueous solution by spraying. You can also use 20-30 grams of chlorothalonil smoke agent per mu each time to fumigate the greenhouse. Apply once every 7-10 days, for 3-5 consecutive treatments.
Root-knot nematode disease The symptoms of cucumber root-knot nematode disease are mainly manifested in the roots. Mildly diseased plants show no obvious symptoms, while severely diseased plants are shorter, poorly developed, and set fruit poorly, and wilt at noon under drought conditions. When diseased cucumber vines are pulled up, root knots of varying sizes can be found on lateral roots or fibrous roots. Some appear in a bead-like series, making the root system thicker. When root knots are dissected, very small milky white root-knot nematodes can be found in the diseased tissue. Prevention and control: Methods such as deep plowing and sun-drying the soil, irrigation during idle periods, and increasing application of decomposed organic fertilizer can be used. If root-knot nematode disease occurs during cucumber growth, drench the roots with 1500-fold solution of 50% phoxim emulsifiable concentrate or 500-fold solution of 30% jiasheng microcapsule suspension emulsion, pouring 0.25-0.5 kilograms of liquid per plant; generally one drenching is enough.