Recently, the National Agricultural Technology Center organized the major potato producing provinces in the north to discuss the occurrence trend of potato late blight. based on the comprehensive analysis of the factors such as the amount of field bacteria, variety resistance and future weather conditions, it is estimated that the occurrence of Potato Late Blight in northern China this year is generally moderate (grade 3), of which the occurrence of Potato Late Blight in central and Western Heilongjiang, along the foot of Xing'an Mountain in Inner Mongolia, central and Western China, northern Shanxi, Zhangcheng area in Hebei and southern Gansu is partial (grade 4), with an area of 11.4 million mu; The epidemic peak period of the disease is from mid July to early August in Northeast China, and from late July to early September in Northwest and North China.
1、 Central diseased plants were found in many fields, and the disease was generally early
Since June, central diseased plants have been found in Datong, Shanxi, Harbin, Heilongjiang, Longnan, Gansu, Yulin, Shaanxi, Chengde, Hebei, Hulunbuir, Inner Mongolia and Songyuan, Jilin. Except that Shaanxi and Jilin are 2-3 days late, most other production areas are 5-14 days earlier than the previous year, and Heilongjiang is 25 days earlier than the previous year. At present, the occurrence area of Potato Late Blight in the main production areas in the north is 401000 mu, which is 9.1% and 45.1% lower than the average value of the previous year and the same period in recent three years (2017-2019); The average diseased plant rate was 0.5% - 3.5%, slightly higher than that in the same period of last year. Among them, 170000 Mu occurred in Gansu, with a year-on-year decrease of 50%. It occurred sporadically in Longnan and Tianshui, with an average diseased plant rate of 0.5%. The highest diseased field rate in Lixian County was 26% and the diseased plant rate was 6%; 100000 mu (sporadic in the previous year) occurred in Heilongjiang, with an average disease plant rate of 1%, and the highest disease plant rate in recurrent fields reached 85%. According to the online monitoring of potato late blight real-time monitoring and early warning system, as of July 12, 27 monitoring points in Heilongjiang, Inner Mongolia, Gansu, Shanxi and other provinces (regions) had been infected for more than three generations (the central disease plant can generally be found in the field of susceptible varieties), accounting for 14.8% of the number of monitoring points in the main potato producing areas in the north, an increase of 0.5 percentage points over the previous year.
2、 Variety distribution and growth period are conducive to disease prevalence
This year, the planting area ratio of potato susceptible varieties in the main production areas of North China is nearly 40%, and that in Shaanxi, Hebei and other provinces is more than 60%. Moreover, the varieties in large-scale planting areas are single, which is conducive to the epidemic of diseases. At present, most potato producing areas are in the bud stage to flowering stage of susceptible diseases. The sowing dates are irregular, the duration of susceptible period is long, the probability is high in case of weather conditions suitable for disease epidemic, and the risk of disease epidemic is high.
3、 The weather conditions are conducive to the epidemic of diseases in some areas
According to the forecast of the National Climate Center, from July to August, except most of Heilongjiang, the temperature in the main potato producing areas in the north is normal or high; Rainy areas are mainly distributed in most of the northeast, most of North China and the east of Northwest China. The rainfall is 1-20% more than usual, including 2-50% more in the east of Heilongjiang and the south central of Shanxi, which is conducive to the infection and epidemic of diseases. In the next 10 days (July 14-23), there will be rainfall in North China, South northeast, southeast northwest and other places. Relevant areas should strengthen monitoring, guard against sudden damage of diseases and do a good job in prevention and control in time.