Melting melon is one of the main economic crops in Yumin County. In 2009, the planting area was 11,067 hectares, accounting for 28.6% of the county's planted area. However, the disease caused by powdery mildew is serious, and the incidence rate is 98%. From mid-July, the disease occurred in the field, and then spread rapidly and reached the peak of the disease in early August.
First, the symptoms
The disease mainly infects leaves and petioles, and the stems are often damaged, and the fruits are less affected. At the beginning of the disease, white powdery mildew spots on the leaf surface gradually enlarge into larger white powdery mildew spots, which soon spread to the leaf back, petiole and even young fruits. In severe cases, the whole plant was white powdery mildew. Covered. In the later stage, the white powder layer turned grayish white, and scattered or piled small grain spots appeared in the white powder layer. In severe cases, the whole plant was killed by melon. The leaves are more sensitive to powdery mildew and will soon die after infection.
Second, the disease conditions
1. Meteorological conditions Powdery mildew produces spores under saturated air humidity, and spores germination is best, but spores cannot germinate in water film. Scattered light is conducive to the survival and germination of conidia, so it often occurs in the shade. Cool temperature around 18 °C, high relative humidity, but no water droplets or water film on the leaf surface, and low light is conducive to the occurrence and development of the disease, stop development below 5 ° C and above 25 ° C, continuous rainfall is not conducive to this disease .
2, cultivation management and extensive management, partial application of nitrogen fertilizer, plant length, dense foliage, poor ventilation, insufficient light, high humidity between plants, plant growth is weak, are conducive to powdery mildew.
Third, the cause of the disease
1. Temperature The overall temperature in May-August 2009 was lower than that in the same period of the previous year. The seedling period was long, the plant growth was slow, and the disease resistance was weak.
2, the humidity hits the melon into the flowering and fruiting period, the water and fertilizer conditions are good, the vines are more leafy, the degree of confinement in the field is obviously improved, the humidity is large, the permeability is poor, and the cloud weather is dominant during the period, and the temperature and humidity conditions in the field are suitable for the disease. The growth of the plant, and the plant from vegetative growth to reproductive growth at this stage, is the weakest period of fighting melon.
Fourth, prevention measures
1. Strengthen management In the field, timely apply organic fertilizer and nitrogen, phosphorus and potassium compound fertilizers to keep the plants ventilated and well-transparent, and the amount of irrigation in the field should be appropriate.
2. Reasonable rotation for reasonable rotation, and rotation with non-melon crops for more than 3 years to reduce pathogens and reduce the incidence of melon disease.
3, seed treatment Before sowing, the fungicides triazolone, methyl thiophanate, dixon, etc. are used for seed dressing to reduce the occurrence of disease in the seedling stage. The melon seeds 4, the chemical control before and after the melon fruiting period is easy to occur, in the field when the disease is not early, the use of chlorothalonil, acetaminophen, ether oxystrobin and other agents for prevention; in the early stage of the field, choose flusilazole, apron The azole, hexaconazole and difenoconazole are used for prevention and treatment, and the prevention and treatment are carried out continuously for 2 to 4 times, once every 7 to 10 days, to effectively control the disease . Reasonable rotation of medication, scientific prevention. Avoid using the same type of medicinal agent continuously to avoid drug resistance and improve control effect. Choose to carry out field control operations in the morning and evening without wind and rain. The water consumption of 667 m 2 is not less than 30 kg, and the spray is even and thorough.
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