2022 Forecast of the Occurrence Trend of the Second-Generation Armyworm

Recently, adult first-generation armyworms have been reported one after another in the Huanghuai, North China, Northeast China, and Northwest China. In parts of the Huanghuai and North China, moth populations are high with distinct peak flights, while egg masses have been observed in multiple fields across Northeast China. Taking weather conditions and crop‑planting patterns into account, the second generation of armyworms is expected to infest approximately 25 million mu nationwide, with overall incidence ranging from light to moderate. In areas with high moth densities and abundant rainfall—particularly in the Huanghuai, North China, and Northeast China—localized fields may experience exceptionally high pest densities. The peak period of infestation and damage is forecast to occur from late June to early July.

The first generation of armyworms is mild, with low residual pest populations.

In the middle and lower reaches of the Yangtze River, the Jianghuai region, and the Huanghuai wheat-growing area, the area infested with armyworms totaled 3.5 million mu, a 28.0% decrease compared with 2021—the smallest such area in the past decade. The average pest density in wheat fields was 0.4 larvae per square meter, down 60% from 2021. Nationwide, control or integrated management measures were applied to 6.58 million mu, with post‑treatment residual pest densities remaining low, all below 0.3 larvae per square meter.

In parts of the Huanghuai and North China regions, the adult population in the current generation is relatively high.

Since late May, the cumulative trap catches of first-generation adults recorded by the high-altitude light-trap monitoring network have been generally elevated at southern monitoring sites. Specifically, Yizhou in Guangxi reported 398 moths, up 34.5% year on year; Anzhou in Sichuan recorded 29 moths, 14.5 times the figure for the same period last year; and Bijie in Guizhou reported 45 moths, down 67.6% compared with the same period last year. By contrast, monitoring sites in North and Northeast China have shown overall lower levels: Luancheng in Hebei and Wanrong in Shanxi recorded 680 and 33 moths, respectively, down 21% and 25% from the corresponding period last year; Jizhou in Tianjin reported 50 moths, unchanged from last year; Yanqing in Beijing recorded 27 moths, just 1.3% of the level during the same period last year (2,037 moths); and Zhangwu in Liaoning and Changling in Jilin reported 20 and 91 moths, respectively—down 31% and up 21.8 times year on year.

In the Huanghuai and North China regions, most pest‑monitoring light traps recorded peak moth flights in late May to early June. In most areas, the cumulative moth catch per trap fell short of last year’s level; however, in several locations in Henan, the cumulative totals exceeded 1,000 moths, and in parts of Hebei, the cumulative catches were markedly higher than last year.

Among these areas, in Changge, Qinyang, Dengzhou, and Yancheng in Henan Province, the cumulative moth counts from early May to June 9 reached 13,624, 4,703, 1,860, and 974, respectively. In Huaiyang, Anyang, Minquan, Mengzhou, Dancheng, and other localities, the cumulative totals ranged from 200 to 820 moths. The peak period for moth attraction occurred from May 31 to June 4, with daily peak counts of 2,490 in Changge, 990 in Dengzhou, 986 in Qinyang, and 600 in Yancheng—levels that were generally 40% to 80% lower than the same period last year.

From May 20 to June 9, the cumulative moth‑attracting counts in Daming, Zhengding, Shenze, Wuqiao, and Guantao, Hebei Province, were 300, 257, 113, 113, and 111 moths, respectively. With the exception of Daming, where the count was 53% lower than the same period last year, the other monitoring sites recorded levels 80% to 3.4 times higher than during the corresponding period last year.

From June 1 to 9, the cumulative moth‑catch totals in Linyi, Yangcheng, Ruicheng, Yanhu, and Wanrong in Shanxi Province were 272, 210, 100, 72, and 48 moths, respectively—down 50% to 90% compared with the same period last year. In contrast, Changzhi, Xiyang, Fenyang, Quwo, and Hongtong, which recorded relatively high catches during the same period last year, now reported only sporadic sightings. In Shandong, during the first ten days of June, the cumulative moth counts were limited to 140–480 moths in Zoucheng, Guangrao, and Juancheng, while all other monitoring sites recorded fewer than 100 moths.

No distinct moth peak was observed in the Northeast region. In Heilongjiang, as of June 6, the cumulative number of moths trapped at all monitoring sites across the province totaled 27. In Jilin, from May 18 to June 9, the total number of moths captured at all monitoring sites reached 169, including 58 in Dehui, 45 in Shuangyang, and 20 in Zhenlai. In Liaoning, Dawawa recorded a cumulative total of 187 moths from June 1 to 9, while Kazuo reported 37 moths from May 27 to June 5, and Zhangwu logged 62 moths from May 31 to June 10—marking the lowest annual count in the past five years. In Inner Mongolia, Kailu County recorded a cumulative total of 24 moths from May 25 to June 8.

In certain counties in the Northwest region, moths were observed at light traps. In Linhe District of Bayannur, Inner Mongolia, the routine monitoring light traps recorded a cumulative total of 60 moths from May 16 to June 7. In Pingluo, Helan, Lingwu, and Zhongning in Ningxia, the routine monitoring light traps captured a total of 180 moths between May 1 and June 12.

Egg masses were detected in multiple field locations across the Northeast region.

Since late May, egg masses have been observed in multiple field locations across Northeast China, with egg counts in some counties of Liaoning exceeding long-term averages. Specifically, in Naiman Banner, Inner Mongolia, 20 straw bundles collected on May 29, June 1, and June 4 yielded one, three, and two egg masses, respectively, with average egg counts of 280, 75, and 62 eggs per bundle. In Kezuo Hou Banner, one egg mass was detected from 10 straw bundles on May 29, while in Kailu County, one egg mass was found from 10 straw bundles on June 6, with egg counts of 280 and 30 eggs, respectively. In Xingcheng, Liaoning, 10 straw bundles on May 29 and June 7 produced two and six egg masses, respectively, with average egg counts of 20–30 and 50–60 eggs per bundle; in Dashiqiao, on June 6 and 9, 10 straw bundles yielded five and two egg masses, respectively, with average counts of 60–70 eggs and a maximum of 102 eggs, indicating egg levels above the long-term norm. In Jiutai, Jilin, 10 straw bundles on June 6 captured two egg masses, with an average count of 110 eggs; on June 7, in Gongzhuling, 10 straw bundles yielded one egg mass containing 80 eggs. In Shuangcheng, Heilongjiang, 10 straw bundles collected on June 10 produced two egg masses, containing 423 and 6 eggs, respectively.

Weather conditions are favorable for the occurrence of armyworms in North China and Northeast China.

According to forecasts from the National Meteorological Center, from late June to early July, eastern Northeast China, northern North China, and eastern Southwest China are expected to experience above-normal precipitation for this time of year, creating favorable conditions for the occurrence and damage caused by the second generation of the Asian corn borer. Meanwhile, parts of North China may experience periods of high temperatures, which could exert a moderating effect on the pest’s development and impact.

Given the strong migratory capacity of adult armyworms and the concealed feeding habits of early‑instar larvae, local authorities should make full use of conventional monitoring lamps, high‑altitude monitoring lamps, sex pheromone traps, and straw bundles to conduct thorough surveillance of adult population dynamics and closely track migration patterns in neighboring areas. At the same time, systematic surveys of egg counts and larval densities should be carried out in millet fields and cornfields with abundant weeds to prevent outbreaks of high‑density, concentrated damage.

Source: National Agricultural Technology Extension