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 of late blight incidence in northern potato-growing regions. Based on a comprehensive analysis of field pathogen populations, cultivar resistance, and climatic conditions, forecasting personnel from seven major potato-producing provinces and autonomous regions in Northeast, Northwest, and North China project that late blight will occur at a generally severe level across most of the northern production areas, with an intensity 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 epidemic period 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 previous 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, the area affected by potato late blight in the major northern production regions stands at 1.446 million mu, 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 down 31.7% and 19.4% from the peak epidemic years of 2012 and 2013. The average incidence rate across regions ranges from 0.1% to 5.2%, higher than during 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 outbreaks have already occurred, with disease 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 Zhalatun, 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 provinces, this proportion exceeds 60%. Due to the large share of seed potatoes retained for personal use, the incidence of pathogen carriage in seed tubers remains relatively high. Moreover, in large‑scale cultivation areas, varietal diversity is limited, creating a planting pattern that facilitates the spread of diseases. At present, potatoes in the main northern production zones are at the bud‑formation to flowering stage—periods when susceptibility to disease is particularly high—and this growth phase lasts for an extended period. Under conditions favorable for disease outbreaks, the likelihood of widespread epidemics increases, thereby elevating the risk of disease dissemination.
　　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 eastern and central Northwest China, central and western Inner Mongolia, North China, and southern Northeast China are forecast to receive above-average rainfall. Specifically, southern Inner Mongolia, eastern Northwest China, and western North China may see 20%–50% more precipitation, increasing the risk of recurrent outbreaks of diseases in these areas.

Source: Pest and Disease Information