Northern regions are on alert for localized outbreaks of second-generation armyworms.

Release Date:

2019-06-14

　Recently, adult second-generation armyworms have been reported one after another in the Jianghuai, Huanghuai, North China, and Northeast regions, with particularly high moth populations and distinct peak activity in some parts of North China. Taking weather conditions and crop‑planting patterns into account, the overall incidence of the second generation this year is expected to be moderate; however, in localized areas of northern provinces such as Hebei and Shanxi—where rainfall has been abundant and management practices are relatively lax—high‑density infestations may occur. The nationwide affected area is projected at 30 million mu, with the peak period of larval damage occurring from mid‑June to early July.
　　I. The first generation of armyworms has a large infested area, with high residual pest densities in localized regions.
　　This year, the area infested by the second generation of the armyworm in the middle and lower reaches of the Yangtze River, the Jianghuai region, and the Huanghuai wheat-growing area totaled 7.18 million mu, a 39.7% increase compared with 2018. Nationwide, the average pest density in wheat fields was 0.6 larvae per square meter, unchanged from 2018. The total area treated—either for control or integrated management—reached 11.53 million mu, and following treatment, the average residual pest density across all types of fields nationwide was 0.4 larvae per square meter, up 33.3% from 2018. However, residual densities remained high in some localized areas; for example, in Anhui, the average residual density after treatment was 1.3 larvae per square meter across all field types.
　　II. In most areas, the adult moth population of the first generation is relatively high.
　　Since late May, adult moth populations have been notably high in Hebei, Shandong, Shanxi, and other regions. In Yongnian District, Hebei, moth counts surged on May 29; from May 29 to June 4, three monitoring lamps recorded cumulative catches of 1,074, 2,892, and 4,232 moths, respectively. In Linxi County, moth numbers spiked on May 31; between May 31 and June 9, a single lamp accumulated 2,993 moths. In Zhengding, a single lamp captured 1,134 moths from May 30 to June 9, while in Luancheng County, a single lamp recorded 653 moths over the same period. In Xianghe, Guantao, and Leting, cumulative catches from June 1 to 9 were 286, 634, and 536 moths, respectively. In Zibo and Feicheng, Shandong, single-lamp totals from June 5 to 11 reached 249 and 499 moths, respectively. In Ruicheng, Shanxi, peak moth activity began on June 3, with a cumulative catch of 614 moths from June 1 to 9. In Yancheng’s Yanhu District, 115 moths were trapped between May 30 and June 2; in Yangcheng, single-lamp catches on May 31, June 4, 7, and 8 were 248, 928, 976, and 340 moths, respectively, with females predominantly at ovarian development stages 1–2. In Changzhi City, a total of 374 moths were collected from June 1 to 9, with 80% of females at ovarian stages 3–4; in Wanrong County, 142 moths were trapped from June 7 to 9.
　　In parts of North China, including Hebei and Beijing, moth counts at high-altitude monitoring stations have been relatively high. In Dongtai, Jiangsu, from May 20 to June 10, a total of 1,128 moths were trapped. In Mengzhou, Henan, 280 moths were captured on May 30. In Wanrong, Shanxi, from June 1 to 10, a cumulative total of 343 moths was recorded. On Changdao Island, Shandong, from May 8 to June 10, a total of 2,628 moths were trapped. In Luanshi, Hebei, moth numbers surged sharply on May 28—earlier than the previous year—and by June 8, 2,184 moths had been trapped; from May 28 to June 10, the cumulative total reached 5,926, 5.3 times the figure for the same period last year. In Yanqing, Beijing, 1,300 moths were trapped on June 3 and 4—more than twenty times the number recorded during the same period last year. In Changling, Jilin, a cumulative total of 71 moths was captured from June 1 to 9, while in Shuangcheng, Heilongjiang, 131 moths were trapped from June 1 to 10—both figures double those of the previous year.
　　III. Weather conditions are favorable for the occurrence of armyworms across most regions.
　　According to forecasts from the National Meteorological Administration, during mid-June, cumulative rainfall in northern North China, Northeast China, and eastern Northwest China is expected to range from 10 to 30 millimeters, with localized amounts of 40 to 60 millimeters, creating conditions favorable for the occurrence of the second generation of the Asian corn borer. Over the next 10 days, temperatures in central and western North China and most of the Huanghuai region are likely to be 1 to 3°C above normal for this time of year, which will exert some adverse effects on the development and damage caused by the second-generation Asian corn borer.
　　Recently, the population of armyworm moths has been high, with a distinct peak; all localities should attach great importance to this situation and conduct thorough field surveys for eggs and larvae. In addition, this year the fall armyworm has spread over a wide area, is moving rapidly, and is causing severe damage. Monitoring and forecasting agencies across regions must closely track the concurrent occurrence and cumulative impacts of armyworms and fall armyworms, issue timely local pest forecasts, and provide comprehensive guidance to ensure timely and effective control measures.