According to the monitoring, this year, the main potato producing areas in the north have sufficient bacterial sources in the field, the disease resistance of planting varieties is not high, and the weather conditions are suitable for the late blight epidemic. It is expected that the late blight of potato will occur moderately in the main producing areas in the northwest, North China and Northeast China, and will occur in some places, such as the central and western parts of Heilongjiang, the great Hinggan Mountains and the foothills of Yinshan Mountain in Inner Mongolia, the southeast and central parts of Gansu, Southern Ningxia, northern Hebei, northern Shanxi and so on; The estimated area is 7.8 million mu. The epidemic peak period of the disease is from mid July to early August in Northeast China, and from late July to late August in Northwest and North China (Table 1).
In most areas, diseases appear early in the field
Local occurrence is serious
According to the prediction of the real-time monitoring and early warning system of potato late blight, at present, there are 148 monitoring points where the pathogen has completed three generations of infection once or more (the central diseased plant is generally visible in the field susceptible varieties), accounting for 38.0%of all monitoring points, a decrease of 2.7 percentage points over the same period last year. Since June, central diseased plants have been found successively in Longnan, Gansu, Datong, Shanxi, Harbin, Jilin Songyuan, Wulanchabu, Inner Mongolia, Yan’an, Shaanxi and other places. Compared with last year, Gansu, Inner Mongolia, Heilongjiang, Jilin and other places are 1-12 days earlier, and Shanxi and Shaanxi are 6 days and 24 days later.
At present, the occurrence area of Potato Late Blight in Shanxi, Shaanxi, Gansu, Heilongjiang and Jilin provinces is 144000 mu, which is 41.9%and 45.6%lower than the average of last year and the same period in recent three years (2019-2021), respectively. The average disease plant rate in various regions is mostly 0.05%- 3%, lighter than that in the same period last year; However, the local occurrence is relatively serious, and the average disease plant rate of Hulan in Heilongjiang and Lishu in Jilin is 6%and 10%respectively.
Potato varieties in most production areas have low resistance
This year, the potato planting area in 8 provinces (autonomous regions) in northwest, North China and Northeast China is nearly 24 million mu. The planting area of susceptible varieties in Hebei, Heilongjiang and other provinces is more than 50%, and the varieties in large-scale planting areas are single, which is conducive to the prevalence of diseases; The planting area of susceptible varieties in Shaanxi, Gansu, Shanxi and Inner Mongolia accounts for 23%- 30%. Although the promotion area of resistant varieties is gradually expanded, which has a certain inhibitory effect on the epidemic of diseases under general weather conditions, there is still a risk of epidemic in case of more precipitation in suitable weather.
At present, most potato producing areas in the north are in the period from budding to flowering, and the susceptible period will continue until the middle and late August to the first ten days of September. It is during the concentrated rainfall period in the north, and the probability of meeting suitable weather conditions is high, increasing the risk of disease epidemic.
Weather conditions are favorable for disease epidemic
According to the prediction of the National Climate Center, from July to August, the temperature in the main potato producing areas in the north is normal or high, and there is more precipitation in the eastern and southern parts of the northeast, North China and the eastern part of the northwest. Among them, the eastern and southern parts of Jilin, Liaoning, most of Hebei, Central Shanxi and Eastern Shaanxi are 20-50%more, which is conducive to the infection and prevalence of potato late blight.