Symptoms and prevention methods of pumpkin spotted disease
(1) Symptoms
Pumpkin spotting disease is harmful to leaves and flower shafts. The leaf spots are rounded to nearly round or amorphous. The leaf margin is black and brown, the junction of the diseased part is moist, and when the humidity is large, the surface of the spot is densely covered with small black spots, and the severe leaf spots are fused, resulting in local dead leaves (Figure 1-). Flower shafts or flower infections are black moist or dark brown decay.
Fig. 1 Diseased leaves of pumpkin spotted disease
(2) Pathogenic characteristics
The pathogen of this disease is Pumpkin leaf spot mold, a synonym of the round leaf spot mold, which belongs to the subphylum fungus of hemiknomycetes. The conidia are scattered or polyphyletic to oblate spherical, dark brown, orificeed. Diameter 65-140 μm: conidia oval, some slightly narrow at one end, unicellular, colorless, sized (5-7) micron X (2-3) microns, conidia emerge from the orifice in a tendrils-like manner when mature, infecting cucurbitaceae. Pumpkin spotted disease can also be caused by "needle spore with melon horn spotted shell", which may be a disease of the same name and have different pathogens.
(3) Occurrence of diseases and epidemic characteristics
The pathogen overwinters in the soil with conidia or mycelium with the remains of the disease, and in the hot and humid season of the next spring, it is mostly seen in August to September in the north. High temperature and humid weather is an important condition for the onset of the disease, low-lying terrain or poor inter-plant closure permeability, and the incidence is severe.
(4) Prevention and control methods
1． Reasonable rotation
To avoid planting in low-lying land, the residue of the former stubble crop should be removed in time before planting, deeply turn the soil, and disinfect the soil with spray disinfectant and 800 times the new high-fat film; and select disease-resistant varieties, and use new high-fat film to disperse underground diseases and insects before sowing, isolate viral infection, and improve seed germination rate.
2． Strengthen management
Timely cultivation and weeding, watering and fertilization, while paying attention to improving inter-plant permeability, and timely spraying to promote The flower king No. 3 during the growth period to inhibit the growth of the main shoot and promote the differentiation of flower buds; spraying strong guatiline before flowering, young fruit stage, and fruit expansion period can increase the thickness of the guati, increase the amount of nutrient transport, promote the rapid development of the melon body, make the melon shape beautiful, juicy and delicious.
3． Pharmaceutical control
At the beginning of the disease, timely spray 70% methylthiopramine wettable powder 800 times liquid + 75% Bacillus Qing wettable powder 800 times liquid, 40% polysulfide suspension 600 times liquid, 50% dinospyridine wettable powder 400-500 times liquid, 50% parahedan wettable powder 1500 times liquid. Pay attention to spraying well, once every 10-15 days, and continuously control 2-3 times. At the same time, with the spraying of new high-fat film 800 times liquid to enhance the efficacy, improve the utilization rate of active ingredients of the agent, and consolidate the prevention and control effect.
Symptoms and prevention methods of pumpkin black star disease