Powdery mildew is a common disease on winter melon, which can harm melon, cucumber, loofah, pumpkin, zucchini, watermelon, melon and other melon crops. Timely pesticide control is the key.
Symptoms primarily harm the leaves. The leaf lesions are nearly round, the edge boundaries are not clear, and the mildew spots are transformed into pink spots. The sporadic pink spots can be fused into a contiguous blocky powder spot. In severe cases, the leaf surface is covered with white powder, and the resulting leaves are Turn yellow and even burn out.
Pathogen: Erysiphecucurbitacearum ZhengetChen and Sphaerothecacucurbitae (Jacz. ZYZhao) are all Ascomycetes subfamily fungi. Both powdery mildews are obligate parasites, and the pathological bacteria have little difference in appearance. Conidiophores are colorless, cylindrical, unbranched, with conidia on them. Conidia are colorless, unitary, elliptic to oblong, and sessile. In the sexual stage, the closed capsule is produced, spherical, brown, without pores, and there are hyphae-like accessory filaments on the surface.
Characteristics of the disease: According to the Chinese Pesticide Network , the pathogens overwinter with the diseased remains in the soil or the melon host in the protected area, becoming the first source of infection in the second year. The germs spread by wind and rain, air currents and water splashes. The spores of the pathogens have strong adaptability to humidity, and can also germinate under the condition of 25% relative humidity, which is often caused by the host under the influence of drought. The most suitable temperature for spore germination of the pathogen is 20-25 Â° C, above 30 Â° C, below -1 Â° C, the spores quickly lose vitality. Protecting sweet potato powdery mildew is more important than open field, insufficient fertilization, soil water shortage, excessive nitrogen fertilizer, excessive irrigation, heavy incidence, poor ventilation in the field, and increased humidity are also conducive to powdery mildew.
Control methods (1) Choose resistant varieties according to local conditions.
(2) Strengthen field management.
Sowing at the right time, reasonably close planting, pay attention to ventilation and ventilation in the field; apply enough base fertilizer, timely topdressing, timely watering, and cultivate strong seedlings; find the diseased plants in the field to remove them in time, remove the diseased residues in the field, and reduce the source of bacteria in the coming year.
(3) Pesticide control.
1 sheds, greenhouses, etc. Before the cultivation of sweet potatoes, they should be sterilized with sulfur powder or chlorothalonil. Every 50m2 with sulfur powder 120g plus sawdust 250g in the pot, put a few points, close the shed in the evening, and ignite the sawdust for a night.
2 pesticide control in the growing season. Pesticide manufacturers recommend using 5% triadimefon (Pulverine) wettable powder 1500 times solution, or 50% polysulfide suspension 300-400 times solution, or 45% diazolone wettable powder 3000-4000 times solution, or The agricultural resistance "120" 150 times, or the Wuyimycin 150 times liquid spray in the early stage of the disease, spray once every 7-10 days, depending on the condition, continuous prevention and control 2-3 times.
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