Identification and Control of Cucumber Bacterial Angular Leaf Spot
Symptoms and Control Methods of Cucumber Bacterial Angular Leaf Spot
Symptoms: It mainly damages leaves, petioles, tendrils and fruits, and can affect plants from the seedling stage to the mature plant stage. When cotyledons are infected at the seedling stage, nearly round, water-soaked, sunken spots begin to appear, which later turn brown and dry up. At the mature plant stage, pinhead-sized water-soaked spots first appear on the leaves. As the lesions expand, they are limited by the leaf veins and become angular, yellow-brown. When humidity is high, milky white mucus is produced on the lesions on the underside of the leaves, and after drying it forms a white film or white powdery substance. In the later stage, the lesions become brittle and easily perforate. The lesions on stems, petioles and young fruit are water-soaked, nearly round to oval, later pale gray; the lesions often crack, and when moist, bacterial ooze exudes from the affected parts on the fruit. The lesions spread into the interior of the fruit, and the flesh along the vascular bundles becomes discolored, extending all the way to the seeds, causing seed contamination. Diseased fruit rot in the later stage and have a foul odor. After young fruit are infected, they often rot and drop early.
Occurrence pattern: This is a disease caused by bacteria. The pathogen overwinters inside or on the surface of seeds or with diseased plant residues in the soil. The pathogen spreads in the field through irrigation water, wind and rain, airflow, insects and farming operations, and enters the host through stomata, wounds and water pores. When humidity is high, the disease is severe, and it tends to become epidemic after storms.
Control measures:
1. Select disease-tolerant varieties.
2. Collect seeds from disease-free fruit.
3. Seed treatment: Cucumber seeds can be sterilized with dry heat in a 70°C constant-temperature chamber for 72 hours, or soaked in 50°C warm water for 20 minutes, then removed, air-dried and sown after sprouting. They can also be soaked in 150-fold 40% formalin solution for 90 minutes, or soaked in 500-fold 1 million-unit streptomycin sulfate solution for 2 hours, then rinsed clean and sown after sprouting.
4. Strengthen cultivation practices to prevent disease: use disease-free soil for raising seedlings, and implement a rotation of more than 2 years with non-cucurbit crops in severely diseased fields. During the growing period, promptly remove diseased leaves and diseased fruit; after harvest, remove diseased plant residues and bury them deeply or burn them.
5. Chemical control: At the early stage of disease, spray 5000-fold new phytomycin solution, 500-fold 30% copper fatty acid emulsifiable wettable powder (DT fungicide), 600-fold 53.8% Kocide suspension concentrate, 800-fold 77% Duoning wettable powder, 800-fold 47% Jiaruinong wettable powder, or 600-fold 70% Zaoshuangtong wettable powder. Use the above agents alternately, spraying once every 7-10 days for 3-4 consecutive sprays. Excessive use of copper preparations can easily cause phytotoxicity, so generally do not use them more than 3 times. Spray carefully onto both the upper and lower surfaces of the leaves to improve control effectiveness.
Occurrence pattern: This is a disease caused by bacteria. The pathogen overwinters inside or on the surface of seeds or with diseased plant residues in the soil. The pathogen spreads in the field through irrigation water, wind and rain, airflow, insects and farming operations, and enters the host through stomata, wounds and water pores. When humidity is high, the disease is severe, and it tends to become epidemic after storms.
Control measures:
1. Select disease-tolerant varieties.
2. Collect seeds from disease-free fruit.
3. Seed treatment: Cucumber seeds can be sterilized with dry heat in a 70°C constant-temperature chamber for 72 hours, or soaked in 50°C warm water for 20 minutes, then removed, air-dried and sown after sprouting. They can also be soaked in 150-fold 40% formalin solution for 90 minutes, or soaked in 500-fold 1 million-unit streptomycin sulfate solution for 2 hours, then rinsed clean and sown after sprouting.
4. Strengthen cultivation practices to prevent disease: use disease-free soil for raising seedlings, and implement a rotation of more than 2 years with non-cucurbit crops in severely diseased fields. During the growing period, promptly remove diseased leaves and diseased fruit; after harvest, remove diseased plant residues and bury them deeply or burn them.
5. Chemical control: At the early stage of disease, spray 5000-fold new phytomycin solution, 500-fold 30% copper fatty acid emulsifiable wettable powder (DT fungicide), 600-fold 53.8% Kocide suspension concentrate, 800-fold 77% Duoning wettable powder, 800-fold 47% Jiaruinong wettable powder, or 600-fold 70% Zaoshuangtong wettable powder. Use the above agents alternately, spraying once every 7-10 days for 3-4 consecutive sprays. Excessive use of copper preparations can easily cause phytotoxicity, so generally do not use them more than 3 times. Spray carefully onto both the upper and lower surfaces of the leaves to improve control effectiveness.