Control of bacterial leaf spot of Hami melon

Bacterial leaf spot is an important disease of Hami melon, which can be caused by planting in protected and open fields. the rate of diseased plants in serious plots or greenhouse is more than 80%. The seriously diseased plants are necrotic due to disease, which obviously affects the production.

The main symptoms are damage to leaves, and when severe, they also infect stems and fruits. The leaves were infected with dark green oil stains at first, then expanded into nearly round to amorphous grayish brown to yellowish brown spots, often with an infiltrating dark green halo on the periphery, and finally showed oil-stained dark brown necrosis. In severe cases, the disease spots on the leaves are connected to each other, resulting in leaf necrosis in a short period of time. After infected with the disease, the stem vine shows a dark green oil stain, cracks and glue in heavy cases, and is easy to rot when the humidity is high. When the fruit is infected, it often produces small green-brown spots on the fruit surface in the initial stage, which is dark green in the periphery, and the disease spots converge to form yellow-brown to brown necrotic spots, which are easy to crack from the disease and rot at last.

Pathogen Pseudomonassyringaepv.Lachrymans (Smith&Bryan) Youngetal. It is called Pseudomonas clove cucumber pathogenic variety, which belongs to bacteria. The cell is short rod-shaped and serially, with a size of 0.7-0.9 μ m × 1.4-2.0 μ m, with 1-5 flagella, capsule and no spores. Gram staining is negative and aggressive. On the meat juice peptone Agar medium, the colony was white, nearly round, flat, slightly protruding in the center, opaque, concentric ring, thin and transparent at the edge, and radial fine hairs at the edge of the colony.

The pathogen overwintered in the seed or in the soil with the disease residue. It invades through wound or stomata, water pores and lenticels, and spreads through Rain Water, watering and insects after the disease. the disease is closely related to condensation or Rain Water. The growth temperature of the pathogen was 1-35 ℃, the suitable temperature for development was 20-28 ℃, the growth stopped at 39 ℃, and the pathogen died at 49-50 ℃. High air humidity, or rainy, or night dew is conducive to the disease.

Prevention and cure method

(1) breeding and planting disease-resistant varieties according to local conditions.

(2) strengthen cultivation management.

Rotation with non-melon crops for more than 2 years; raising seedlings with disease-free soil and timely transplanting; scientific fertilization, increasing application of phosphorus and potassium fertilizer to improve plant disease resistance; reasonable watering, preventing flood irrigation, paying attention to ventilation and humidity reduction in protected land, shortening plant surface condensation time, paying attention to agricultural operation after dew drying, timely control of field pests; timely uprooting of diseased plants in the field, and thorough removal of residual leaves after pulling seedlings to reduce the source of infection.

(3) seed treatment.

Select disease-free seeds, soak the seeds in 50-52 ℃ warm water 30min before sowing, or choose 47% Ruinong wettable powder with 0.3% seed weight to mix the seeds.

(4) Pesticide control.

For chemical control at the initial stage of the disease, 5% Garinon dust agent 15kg/hm2 can be selected for powder control. It can also be treated with 47% plus Ruinong wettable powder 600x liquid, or 77% Kaizao wettable powder 500x liquid, or 25% dithienone plus alkaline copper chloride water agent 500x liquid, or 25% thiumazole 300x solution, or 5000 times neophenomycin spray.

Commonly used agents add Ruinong, Kexade, dithienone, thiumazole, neoptomycin.