The recurrence of late blight in northern potato crops is clearly pronounced.

　　Recently, the National Agricultural Technology Extension Center convened an online consultation on the forecast for the occurrence trend of potato late blight in northern China. Based on a comprehensive analysis of field pathogen populations, cultivar resistance, and climatic conditions, forecasting technicians from seven major potato-producing provinces and autonomous regions in Northeast, Northwest, and North China project that late blight will generally be severe across most of the northern production areas, with a level of incidence markedly higher than in the past three years. In particular, localized epidemics are expected in southeastern Gansu and central‑eastern Inner Mongolia, affecting approximately 16.6 million mu. The peak period of disease spread is projected to occur from late July to mid‑August in most of Northeast and North China, and from late July to early September in the Northwest.
　　Basis for the forecast
　　Diseases appear early, and the current incidence is more severe than in the past three years.
　　Since mid-June, central diseased plants have been detected in succession across Gansu’s Longnan and Tianshui, Heilongjiang’s Harbin, Inner Mongolia’s Hulunbuir, Shanxi’s Datong, Hebei’s Chengde, and other localities—3 to 10 days earlier than last year, and in some areas up to 30 days earlier. At present, late blight has affected 1.446 million mu of potato acreage in the major northern production regions, representing increases of 380% and 100% compared with the same period last year and the three-year average (2015–2017), respectively; however, these figures are still 31.7% and 19.4% lower than during the peak epidemic years of 2012 and 2013. The average incidence rate across regions ranges from 0.1% to 5.2%, higher than in the same period over the past three years. In Gansu, the affected area totals 1.285 million mu, an increase of 1 million mu year on year; in Longnan and Tianshui, widespread disease has already emerged, with severity approaching that of the 2012 epidemic, and in severely re‑infested fields, the highest incidence has reached 100%. According to the China Potato Late Blight Real-Time Monitoring and Early Warning System, as of July 14, 60 monitoring sites in provinces and autonomous regions—including Heilongjiang, Inner Mongolia, Gansu, Ningxia, Shaanxi, and Shanxi—have reported three or more generations of infection (with central diseased plants visible in fields of susceptible varieties), accounting for 46.8% of all monitoring points—a 32-percentage-point increase over the same period last year. Notably, in Gansu’s Lintao, Zhuanglang, and Gangu counties, Heilongjiang’s Dongning County, Inner Mongolia’s Zhalantun, Ningxia’s Pengyang County, Shaanxi’s Dingbian County, and Shanxi’s Wuxiang County, five or more generations of infection have been recorded.
　　Varietal distribution and the growth period are conducive to disease epidemics.
　　According to statistics, this year the potato‑growing area in China’s major northern production regions totals approximately 32 million mu, with nearly 50% of planted acreage affected by disease; in Gansu, Shaanxi, Hebei and other areas, this proportion exceeds 60%. Due to the large share of seed potatoes retained for replanting, the incidence of pathogen carriage in seed tubers remains relatively high, and the monoculture of a limited number of varieties in large‑scale cultivation zones further facilitates disease spread. At present, potatoes in the main northern production areas are at the susceptible stage—from bud formation to flowering—a phase that lasts for an extended period. Under conditions favorable to disease outbreaks, the likelihood of widespread epidemics is heightened, thereby increasing the risk of severe disease incidence.
　　Weather conditions are highly favorable for the epidemic of the disease.
　　According to forecasts from the national meteorological authorities, over the next 10 days (July 16–25), eastern Northwest China, northern North China, and northern Northeast China are expected to experience above-normal precipitation, with most areas seeing 30%–80% more rainfall and some localized areas receiving more than double the usual amount. From mid-July to mid-August, temperatures in the major potato-producing regions of northern China are likely to be near normal, while precipitation in central and eastern Northwest China, central and western Inner Mongolia, North China, and southern Northeast China is projected to exceed average levels. Specifically, southern Inner Mongolia, eastern Northwest China, and western North China are expected to see 20%–50% more rainfall, increasing the risk of recurrent outbreaks of diseases in these areas.

Source: Pest and Disease Information