The National Agricultural Technology Center has issued an early warning: adult armyworms are appearing one after another in the Jianghuai, Huanghuai, North China, and Northeast regions.

Recently, the National Agricultural Technology Extension Center released its latest plant pest and disease report: In recent days, adult first-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 areas of North China.

Taking into account weather conditions and crop‑planting patterns, the second generation of armyworms is expected to infest approximately 30 million mu nationwide, with an overall moderate level of occurrence. In localized areas—such as Northeast China, the Huanghuai region, and Southwest China—where rainfall has been abundant and management practices are lax, high‑density patches may develop. The peak period of infestation and damage is anticipated from mid‑June to early July.

The Harm Caused by the Corn Earworm

The armyworm is characterized by long-distance migratory flight and concentrated outbreaks, primarily infesting cereal crops such as wheat and maize, as well as cotton, legumes, and vegetables.

The corn earworm feeds voraciously on corn leaves as a larva; in severe outbreaks, it can strip the foliage within a short period, leading to yield reductions or even total crop failure. The primary damage is caused by larvae chewing on leaf tissue. First- and second-instar larvae create small holes, while older instars leave irregular notches; during intense feeding, they may consume entire leaves. In large-scale infestations, the leaves are completely defoliated, leaving only the veins, resulting in severe yield losses or even total crop loss. When one field is entirely consumed, the larvae often migrate in dense, single-file bands to neighboring fields, which is why this pest is also known as the “armyworm.” Fields that are low‑lying, with uneven plant heights, and heavily infested with weeds tend to suffer the most severe damage.

The local residual pest population of the armyworm is high in this generation.
 

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 7.86 million mu, up 9.4% from 2019. The average pest density in wheat fields was 0.3 larvae per square meter, a 23% decrease compared with 2019. Nationwide, control measures were implemented on 11.58 million mu; however, post‑treatment residual pest densities remained high in some localized areas—for example, in Anhui, the average residual density across all field types was 1.3 larvae per square meter.

Adult moth populations are high in southern and northeastern regions.
 

According to high-altitude light-trap monitoring results from late May, the cumulative catch of first-generation adults in southern China was significantly higher than usual. In Yizhou, Guangxi, the count reached 1,001 moths—ten times the 2015–2018 average. In Zaoyang, Hubei, the numbers were 14,772; in Anlu, 7,750; in Zhongxiang, 2,295; and in Dangyang, 1,877—each exceeding long-term averages. In Dongtai, Jiangsu, the count stood at 275, more than ten times the level recorded during the same period from 2015 to 2018, though 40% lower than in 2019.

In North and Northeast China, moth‑catching lamps typically recorded peak emergence in the first ten days of June, with overall moth counts lower than both last year and the long-term average. In many parts of Hebei, moth numbers surged on June 1: in Pingxiang, a single lamp captured 113 moths in one day, with a cumulative total of 379 over June 1–3; in Yongnian District of Handan, daily catches at a single lamp jumped from fewer than 10 to 51 on June 1; and in Anxin, a single lamp attracted 39 moths on that same day. In Shanxi, at Yanhu, a single lamp accumulated 525 moths between May 30 and June 7, with 113 and 109 moths caught on June 6 and 7, respectively. In Jincheng, a single lamp recorded a cumulative total of 150 moths from June 1 to 7, with 55 and 48 moths captured on June 1 and 2, respectively. At the remaining 35 monitoring sites, average daily catches per lamp have remained below 5 since late May. In Jianping, Liaoning, a peak emerged on June 9, with a single lamp capturing 190 moths; the sex ratio was 5:1, and 96% of the females had ovaries at stage 3. In Beipiao, a single lamp has accumulated 68 moths since May 20, while in Fakou, a single lamp recorded a cumulative total of 34 moths from June 6 to 8.

Since May 20, the cumulative moth catch at high-altitude light-trap monitoring sites in northern China has been as follows: Mengzhou, Henan, with 591 moths—3.7 times the 2015–2019 average; Changdao, Shandong, with 548 moths, significantly lower than the 2017–2019 level; Zhangwu, Liaoning, with 137 moths, peaking at 20 on June 8; Shuangcheng, Heilongjiang, with 229 moths—the highest count since 2015 and 2.5 times the three-year average, with a peak of 45 on June 4; Lulong, Hebei, with 13 moths; Changling, Jilin, with 11; and Xingping, Shaanxi, with 12.

Egg masses detected in the Northeast region
 

In Tongliao, Inner Mongolia, egg masses began to appear successively after mid-May. On May 20, five straw‑bundle traps yielded an average of 125 eggs per trap; by June 7, eleven traps had produced an average of 89 eggs each. In Kezuo Rear Banner, Naiman Banner, and Kezuo Middle Banner, single‑day straw‑bundle traps captured 3–4 bundles, with an average of 65–76 eggs per bundle. In Beipiao, Liaoning, one straw‑bundle trap on May 30 contained 82 eggs, with emergence occurring earlier than last year’s June 6. In Shenbei New District, two and four straw‑bundle traps were deployed on June 3 and June 6, respectively, yielding averages of 35 and 80 eggs per trap. In Xingcheng, from May 27 to June 9, 18 traps collected eggs, with an average of 50 eggs per trap. In Changling, Jilin, egg masses were first observed on June 3; three straw‑bundle traps set up for this purpose captured a total of 15 egg masses, averaging 52 eggs each. In Shuangcheng, Heilongjiang, egg masses were detected on June 5; ten straw‑bundle traps yielded six egg masses, with an average of 101 eggs per trap.

Weather conditions are favorable for the occurrence of armyworms in the middle and lower reaches of the Yangtze River and in Northeast China.
 

According to forecasts from the National Meteorological Administration, in June, the central and northern parts of Northeast China, the Jianghuai region, most of the Jianghan Plain, the Jiangnan region, and the central part of Northwest China are expected to experience above-normal precipitation and temperatures that are either below or near normal for this time of year, conditions that are highly favorable for the occurrence and damage caused by the second generation of the armyworm. In contrast, North China and the Huanghuai region are likely to see 20%–50% less rainfall and temperatures 1°–2°C higher, which will exert a certain inhibitory effect on the development and harm caused by the second-generation armyworm.

Given the adult armyworm’s strong migratory capacity and the cryptic feeding habits of its early‑instar larvae, local authorities should make full use of monitoring tools such as pest‑monitoring lamps, high‑altitude surveillance lights, and willow‑twig traps to closely track the pest’s population dynamics. They should also conduct thorough field surveys for eggs and young larvae to prevent the emergence of high‑density, concentrated outbreaks.

Source: National Agricultural Technology Center, Agricultural Technology, China Grains Network, Seed Industry Business Network