Symptoms and Control methods of Cucumber bacterial Corner spot

Symptoms: it mainly harms leaves, petioles, tendrils and fruits, and can be damaged from seedling stage to adult stage. At the seedling stage, the cotyledons were infected, and nearly round water-immersed sunken spots began to occur, and then turned brown and withered. At the adult stage, the size of the primary needle on the leaf is water-stained spots, and the enlargement of the disease spot is polygonal due to the limitation of the leaf vein. when the humidity is high, milky mucus is produced on the disease spot on the back of the leaf, and a layer of white film or white powder is formed after drying. the disease spot is brittle and easy to perforate in the later stage. The diseased spots on stems, petioles and young melon strips are immersed in water, nearly round to oval, and then light gray, and the disease spots often crack. When it is wet, the disease spot overflows the bacterial pus on the disease part of the melon strips, and the disease spots spread to the inside of the melon strips, changing color along the vascular bundles and extending all the way to the seeds, causing the seeds to carry bacteria. Diseased melons rot in the later stage, with a bad smell, and young melons often rot and fall early after being killed.

Occurrence regularity: a disease caused by bacteria that overwinters in the soil inside or outside the seed or in the soil with the disease residue. The pathogen spreads in the field through irrigation, wind and rain, airflow, insects and agricultural operations, and is immersed into the host by stomata, wounds and water holes. With high humidity, the disease is easy to be prevalent after the storm.

Prevention and control measures:

1. Select disease-resistant varieties.

2. Collect seeds from disease-free melons.

3. Seed treatment: melon seeds can be sterilized in 70 ℃ thermostat for 72 hours, or soaked in 50 ℃ warm water for 20 minutes, removed and dried, and soaked in 40% formalin for 90 minutes, or soaked in 1 million units of streptomycin sulfate for 2 hours.

4. Strengthening cultivation and disease prevention, raising seedlings in disease-free soil, and rotation of seriously diseased fields and non-melon crops for more than 2 years. Timely removal of diseased leaves and melons during the growing period, removal of diseased bodies after harvest, deep burial or burning.

5. Chemical control: spraying 5000 times of neophymycin, 53.8% of copper succinate (DT fungicide), 77% of Dorin wettable powder, 47% of Ruinong wettable powder, 70% early frost copper wettable powder, the above agents were used alternately and sprayed every 7-10 days. Excessive use of copper preparation is easy to cause drug damage, generally no more than 3 times. Spray should be carefully sprayed to the front and back of the leaves, which can improve the control effect.