Huizhou City Melors Plastic Products Co., Limited , https://www.foampioneer.com
First, the main symptoms of rapeseed strains are initially close to the ground stems and leaves appear dark depression spots. When the humidity is high, light brown spider filamentous mycelium grows on the lesions, and the diseased leaves are wilted and yellow and easily fall off. The roots and stems of the seedlings were damaged, brown spots appeared on the base of the stems or near the ground, and they were slightly sunken. Afterwards, they gradually shrank, and the roots and stems were fine and the diseased seedlings were folded. In the adult phase, the rhizomes are enlarged, and the roots are covered with gray-black depressions. The roots are slightly soft, and the main roots are easy to pull off. There are usually a few secondary roots in the upper part of the cuttings. When the seedlings are severe, the whole plant is withered and the wintering period is not tolerant to cold, and it is vulnerable to freezing and dead seedlings.
Second, the incidence of the law of rape root rot is a fungal disease, the disease is mainly in the mycelium or sclerotia in the soil or in the sick plants overwintering and over-summer, in the soil camp rot life, viability can be maintained for more than 2 years Sick soil is the main source of infection. The optimum temperature for the development of the bacteria is about 25°C. It is easy to infect the host under the conditions of rainy weather. The disease is often accompanied by waterlogging in our country. In general, during the sowing period, it suffered from continuous rain. The weather of Linyufa at the Plant Protection Station in Quanzhou County, Anhui Province caused rotting and cultivating. The seedling rape seedlings and early planting rapeseed seedlings in the field would have an early onset and were of serious concern. Followed by soil viscous, too long seedling age, poor drainage in the field is also aggravating the main cause of the disease. According to the investigation of the incidence of field diseases, the resistance of different varieties to rape root rot was not significantly different, but there was no completely resistant variety. I am in mid-October. Rape seedlings in the 3-5 leaf stage is the main stage of the disease. With the decrease of temperature, the disease expansion rate is also slowed down.
Third, comprehensive control measures
l. Implement rotation to avoid redoing. The rape planting area was replanted as far as possible for two consecutive years, avoiding the re-planting of cruciferous crops. Choose the ideal disease-free field nursery base for soil structure to reduce the initial infection path of root rot.
2, fine soil preparation, drainage ditch. After the rapeseed planting and sowing sites are selected, the ridges should be ploughed in time, rake the trenches and apply ripened agricultural fertilizers. Really do not rain water in the sky, the ditch no water. For the low-lying and easy-to-sweep fields, high sorghum trenches should be used to reduce the soil moisture in time, promote the development of the roots of the seedlings, and increase the resistance of the plants.
3, reasonable close planting, appropriate time seedlings. The seedbed period is a critical period to prevent the infection of rape root rot. According to the characteristics of different varieties of rapeseed, a reasonable sowing amount should be determined. After seedling age, the seedlings should be planted after 3 leaves, and the weak seedlings should be removed to improve the light and ventilation of the seedbed, reduce the humidity between the plants, reduce the incidence of seedlings, and cultivate robust seedlings. .
4, chemical control. (1) When the seedbed is selected, 50.6kg of lime powder is applied per 667m2 of ploughing; or at the time of seedbed regrowth, 7% of the 667m2 is made of 70% of dexamethasone wettable powder (1kg), and 3Okg of dry fine soil is mixed. Inside the soil, carry out soil treatment. (2) Rapeseed seedlings have just entered the early stage of onset of disease, they should grab sunny days and adopt chemical control in a timely manner to prevent the disease from expanding. 667m2 with 75% chlorothalonil WP wettable powder 600-700 times; or 50% carbendazim WP 800-1000 times; or 70% dexamethasone WP 1000 times; 667m2 spraying liquid 60kg. Severe disease fields were sprayed once every 7 days for 2-3 times, which had better preventive and therapeutic effects.
Rape root rot
Rape root rot is the main disease of rape seedlings. In recent years, with the adjustment of planting structure. The area of ​​rapeseed in Chongming has been expanding year by year. In 1999, the planting area of ​​rapeseed in the county reached 24,000 hm2, of which hybrid seedling transplanting area accounted for about 85%. Due to the limitation of the planting structure of rapeseed and other undesirable factors, the occurrence of root rot of rapeseed is becoming more and more serious. According to field surveys, the incidence rate of strains is generally 3% to 5%, and heavy hazard fields are as high as 10% to 20%, which poses a serious threat to the expansion of rapeseed production and safe wintering of vegetable seedlings.