Analysis and Forecast of the National Autumn Locust Outbreak Trend in 2018

Release Date:

2018-07-17

　　The National Agricultural Technology Center convened the 2018 National Autumn Locust Outbreak Trend Consultation Meeting in Songyuan City, Jilin Province. Based on an analysis of factors such as the baseline population of residual summer locusts, the ecological conditions of locust‑infested areas, and meteorological conditions, survey and forecasting technicians from provinces, autonomous regions, and municipalities where locusts occur issued forecasts for the autumn locust outbreak trend.
　　Analysis and Forecast of the National Autumn Locust Outbreak Trend in 2018
　　1. Trend of occurrence
　　(1) East Asian migratory locust
　　The autumn outbreak of the East Asian migratory locust is expected to be generally mild, with moderate infestations in locust‑prone areas such as Shandong and the Bohai Bay region around Tianjin. In particular, high‑density locust nymph patches may occur in reservoirs and ecological protection zones—including Beidagang in Tianjin’s Binhai New Area and Xiashan in Shandong—as well as in Hancheng (Shaanxi), Puyang (Henan), Xiangzhou (Guangxi), and Dongfang (Hainan). The total affected area is projected at 7.3 million mu, with 3.58 million mu requiring control measures. The peak emergence of locust nymphs in major infestation zones is expected from late July to early August, while the peak of third‑instar nymphs will occur in mid‑to‑late August.
　　(2) Tibetan migratory locust
　　It is forecast that the Tibetan migratory locust will occur at a moderate level across most of its habitual outbreak areas in Sichuan and Tibet, with locally heavier infestations along the Jinsha River, Yarlung Tsangpo River, and Nianchu River basins; isolated patches of high-density nymphs may also emerge. The total affected area is estimated at 1.2 million mu, with 800,000 mu requiring control measures. The peak period of occurrence is expected from mid-July to early August.
　　(3) Asian migratory locust
　　It is anticipated that the Asian migratory locust will occur at a generally low level in Xinjiang, Jilin, and Heilongjiang, though there remains a possibility of imported swarms from abroad causing damage in areas such as Tacheng and Altay. The affected area is projected to be 250,000 mu, with 80,000 mu requiring control measures; the peak period of occurrence is expected to span from mid-July to late August.
　　(4) Desert locust in the northern agro-pastoral ecotone
　　It is forecast that the northern agro-pastoral ecotone will experience generally moderate outbreaks of locusts, with heavier infestations expected in central and western Heilongjiang. The total affected area is estimated at 17.75 million mu, of which 4.20 million mu will require control measures. The peak outbreak period is from late July to mid-August, with the main species involved including the Asian small grasshopper, the yellow‑shanked grasshopper, the clumsy grasshopper, the red‑winged knotted‑knee grasshopper, the pasture grasshopper, and the broad‑winged curved‑back grasshopper.
　　2. Basis for Forecasting
　　(1) The area occupied by summer residual populations of the East Asian migratory locust is lower than both last year’s level and the recent multi-year average.
　　According to statistics from various locust‑infested areas, the area occupied by summer residual populations of the East Asian migratory locust totaled 6.251 million mu, down 13.0% year on year and 18.2% compared with the five‑year average. Specifically, Shandong, Henan, and Hainan saw reductions of 468,000, 207,000, and 103,000 mu, respectively, while Hebei, Jiangsu, Anhui, and Shanxi experienced decreases of 19,000 to 77,000 mu. By contrast, Shaanxi and Tianjin recorded increases of 48,000 and 40,000 mu, respectively, and Guangxi and Liaoning remained virtually unchanged from the previous year.
　　In the major locust‑infested areas, the average density of summer residual East Asian migratory locusts was 12 per mu, higher than last year’s 9.4 and the five‑year average of 11.3. The areas with densities of 6–10, 11–30, 31–100, and over 100 per mu totaled 3.80 million, 1.867 million, 0.50 million, and 8,400 mu, respectively—down 13.6%, 19.9%, 3.5%, and 71.7% year on year, and 21.9%, 11.2%, 17.9%, and 1.3% below the five‑year averages. High‑density residual locust patches exceeding 100 per mu were reported in Anxin and Dacheng in Hebei, Beidagang in the Binhai New Area of Tianjin, Dongming and Xiashan in Shandong, Hancheng and Dayi in Shaanxi, Puyang in Henan, Yingshang in Anhui, Xiangzhou in Guangxi, and Dongfang in Hainan.
　　(2) The initial population levels of the Tibetan migratory locust and the Asian migratory locust decreased slightly compared with the previous year, while the initial population levels of the desert locust in northern agro-pastoral areas were higher than last year.
　　Currently, the Tibetan migratory locust is infesting 153,000 mu in Sichuan, roughly unchanged from last year. The average nymph density stands at 5 per square meter, lower than last year’s 7.6 and the five-year average of 7. By contrast, the Asian migratory locust is present on 145,000 mu, a 13.2% year-on-year decrease, with an average nymph density of 0.1 per square meter—level with the past two years. In the northern agro-pastoral ecotone, the desert locust is currently affecting 18.82 million mu, up by 55,000 mu compared with the same period last year; the average population density is 8.8 per square meter, higher than last year’s 6.
　　(3) Climatic and ecological conditions are generally favorable for locust outbreaks.
　　According to forecasts from the National Climate Center, during July and August, temperatures across China’s major locust‑infested regions are expected to be generally above normal, while precipitation is likely to be above average in the Bohai Sea rim, the Yellow River floodplains, and parts of Northwest China. In contrast, locust‑prone areas such as northern Xinjiang, northeastern Inner Mongolia, and western Heilongjiang are forecast to experience normal or below‑normal rainfall, with no significant adverse impact on locust outbreaks.
　　The complex ecological environment in locust‑infested areas increases the risk of locust outbreaks. Water and sediment regulation at the Xiaolangdi Reservoir on the Yellow River has led to an expansion of young floodplains, chicken‑heart sandbars, and inter‑river sandbars, while declining reservoir water levels and expanding wetland areas have created new suitable habitats for locusts, thereby heightening the potential for high‑density, localized outbreaks.