Forecast of the Occurrence Trends of Corn Diseases and Pests in the Second Half of 2019

Release Date:

2019-07-30

From July 22 to 24, the National Agricultural Technology Center convened the 2019 National… in Lanzhou, Gansu Province. Corn A consultation meeting on the trends of pest and disease outbreaks was held, with participants from across the country. Corn The pest‑monitoring and forecasting technicians from the producing provinces, autonomous regions, and municipalities, together with relevant experts from research and educational institutions, have summarized… Corn Based on the pest and disease incidence in the first half of the year, and taking into account the current baseline levels of pest and disease occurrence, Corn Based on a comprehensive analysis of planting practices and crop arrangements in conjunction with future climate factors, it is projected that in the second half of this year… Corn The severity of pest and disease outbreaks will be significantly higher than last year and the long-term average, with migratory pests such as the fall armyworm, the third-generation armyworm, the second-generation grass webworm, and the cotton bollworm posing a threat to… Corn The production threat is significant, Corn Sesamia, large spot disease, and brown spot disease are widespread; the peak period of damage in most of northern China occurs from late July to late August, while in southern China… Corn The planting season is sustainable until the end of October.

　　I. Overview of Incidents in the First Half of the Year
　　First half of the year Corn Overall, the severity of pest and disease outbreaks was greater than last year, with a total affected area of 327 million mu‑times. Pest infestations accounted for 310 million mu‑times, while disease occurrences totaled 17 million mu‑times. Among these, migratory pests such as the second-generation armyworm, fall armyworm, and first-generation grass webworm caused particularly severe damage, along with underground pests and the first generation… Corn Borer pests are widespread, and the second generation of cotton bollworm, the two-spotted armyworm, and thrips have become increasingly damaging in certain areas of the Huang-Huai-Hai region.
　　The fall armyworm has been reported in 21 provinces, with an actual infested area of 11.88 million mu. It is characterized by a wide distribution, rapid expansion, and severe damage; in parts of the Southwest and South China, pest densities are high and the percentage of damaged plants is elevated. The second generation of the common cutworm has affected 50 million mu, significantly more than during 2014–2018, with localized areas or fields in the Southwest, Northwest, Northeast, and North China experiencing recurrent outbreaks. The grass webworm has entered a new cycle of occurrence: the first generation is moderately to heavily prevalent in Inner Mongolia and adjacent areas of Shanxi, Hebei, and Shaanxi, covering 3.2 million mu. The two-spotted armyworm has infested 15 million mu, with heavier-than-last-year outbreaks in certain localities of Tianjin, Shanxi, Hebei, and Shandong. Underground pests have spread over 88 million mu, with widespread incidence in parts of Northeast, North, and Northwest China, and locally severe damage. Corn In Northeast China, North China, the Huang-Huai region, and Southwest China, the incidence of stem borers was close to the long-term average, with an affected area of 45 million mu. The second generation of cotton bollworms and thrips were particularly prevalent across much of the Huang-Huai–Hai region, affecting 30 million mu.
　　Sheath blight and rough dwarf disease were relatively severe in the early stages, affecting over 3 million mu of land, while northern corn leaf blight, southern corn leaf blight, and rust were observed across various… Corn Diseases have been observed in the production areas one after another, but the overall severity remains mild.
　　II. Trends in the Second Half of the Year
　　It is expected that in the second half of the year, nationwide… Corn Pests and diseases occurred on 860 million mu of farmland, with pest infestations affecting 580 million mu and disease outbreaks affecting 280 million mu.
　　Migratory pests in the second half of the year Corn Production faces the greatest threat, with the fall armyworm primarily damaging the Southwest, South China, and the Jiangnan region during the summer and autumn seasons. Corn In certain regions—particularly those in Yunnan, Guangxi, and other areas where local pest populations undergo multiple generations of reproduction and where imported pests continue to invade—the damage is most severe. In the Huanghuaihai Plain and Northwest China, the affected area will continue to expand, with outbreaks generally occurring in localized patches or sporadically; the nationwide infested area is estimated at 20 million mu. For the third generation of the armyworm, moderate incidence is expected, with high‑density, concentrated damage likely in parts of Northeast China, North China, and Southwest China, covering approximately 35 million mu. The second generation of the grass cutworm is highly likely to occur at a severe level in Inner Mongolia and adjacent areas, affecting about 6 million mu. As for the third and fourth generations of the cotton bollworm, they may reach a moderately severe level in the Huanghuaihai region, while other areas will see moderate outbreaks, with a total affected area of 60 million mu. Corn The stem borer is moderately prevalent across most of Northeast China, North China, the Huanghuai region, and Northwest China, with a cumulative affected area of 260 million mu‑times. Aphids are moderately prevalent in much of Northeast China, North China, and Northwest China, affecting 75 million mu. Spider mites and the two-spotted leaf beetle are moderately prevalent in certain areas of Northwest China and North China, each affecting 30 million mu. Grasshoppers may cause some damage in parts of the arid regions of northern China, affecting 10 million mu.
　　Large spot disease is prevalent across most of Northeast China, northern North China, and eastern Northwest China; small spot disease occurs in southern Huanghuai and localized areas of Southwest China; brown spot disease is observed in the Huanghuai–Hai region; and Curvularia leaf spot is reported in the Huanghuai area and southern Northeast China, with incidence levels similar to those of a typical year.
　　III. Forecast Basis
　　(1) Migratory pests have a wide source range, and in some areas their initial population levels are high.
　　The fall armyworm has been detected in 1,246 counties across 21 provinces nationwide. Thanks to intensive control efforts, the overall pest population has declined significantly. However, due to the pest’s strong reproductive capacity and the difficulty of managing older-stage larvae, a residual baseline persists, while continued immigration of foreign‑origin populations is further increasing its numbers. Monitoring indicates peak moth catches at sex pheromone traps in the Jiangnan region and the middle and lower reaches of the Yangtze River: in Xinfeng, Jiangxi, 53 moths were trapped from June 21–23; in Jianghua, Hunan, 561 moths were captured from July 5–7; and in Shishou, Hubei, 72 moths were collected from July 5–11. Since late June, high‑altitude light traps in Yunnan, Guangxi, and other areas have recorded distinct moth peaks: in Jiangcheng, Yunnan, a cumulative total of 2,543 moths was attracted from June 26 to July 13, with 311 and 273 moths caught on July 3 and July 5, respectively; in Yizhou, Guangxi, 822 moths were trapped from June 23 to July 13, including 132 on June 26 and 97 on July 5, underscoring the ongoing influx of overseas pest sources.
　　The second generation of armyworms has infested large areas in the Southwest, Northwest, Northeast, and North China, with locally high pest densities in some regions, particularly in the Southwest. Recently, adult counts recorded by high-altitude light traps across various locales have been markedly elevated. In Yizhou, Guangxi, where this pest is typically absent during July, exceptionally high populations were captured: 7,379 moths from July 2 to 15, with peaks of 3,000 on July 7 and July 10; in Luan County, 2,320 moths were trapped from July 17 to 25, approaching the average levels observed from 2014 to 2018; in Shuangcheng, Heilongjiang, 272 moths were collected between July 18 and 24—double the figure for the same period last year; and on Changdao Island, Shandong, 933 moths were recorded from July 5 to 23, three times the average for the corresponding period from 2014 to 2018.
　　The first generation of the grass cutworm has emerged in more than 40 banners and counties across 11 leagues and cities, including Hinggan League, Hohhot, and Ulanqab in Inner Mongolia. High residual populations persist in grasslands and woodlands surrounding farmland. Recently, some counties in Hulunbuir and Hinggan League have experienced a peak in adult emergence; in Ulanhot, on July 23, light traps recorded over 20,000 moths, with 90% of females exhibiting ovarian development stages 2–3. In Datong, Shanxi, field counts on July 23 revealed 150 moths per 100 steps, while in Kangbao, Hebei, light traps captured 450 moths between July 20 and 21. In parts of Hulunbuir, second-generation larvae have begun to appear, with larval densities ranging from 2 to 3 individuals per square meter in agricultural fields.
　　A generation Corn The average number of stem borers per 100 plants was 20 in Heilongjiang, 35 in Guizhou, 30 in Yunnan, and 12 in Jiangsu; in other provinces, the figure was below 10, with baseline levels lower than usual.
　　(2) Corn The growth period and cultivation practices are conducive to the occurrence of pests and diseases.
　　North Corn Continuous monoculture leads to vigorous, tall plant growth and dense canopy closure in the field, creating favorable conditions for the occurrence of diseases and pests. In particular, fields with lax management and abundant weeds provide ideal conditions for the oriental armyworm and the rice stem borer to concentrate their egg‑laying and cause significant damage. Southern regions. Corn Intercropping, summer–autumn season Corn The timing of the growing season varies, creating favorable conditions for fall armyworm feeding and damage, which intensifies with each successive generation. In addition, at present, in regions such as the Huang-Huai-Hai Plain and Northwest China… Corn Most are in the trumpet‑mouth stage, which corresponds to the optimal phenological period for fall armyworm damage.
　　(3) Future meteorological conditions across most regions Corn Favorable conditions for the occurrence of diseases and pests
　　According to forecasts from the National Climate Center, southern Northeast China, eastern North China, and northeastern Huanghuai will experience 20%–50% above-normal precipitation in August, creating favorable conditions for the occurrence of armyworms, grass cutworms, and plant diseases. In most of North China, Huanghuai, and Jianghuai, temperatures during August and September are expected to be 1°–2°C higher than normal, with precipitation at or below average, which will promote damage caused by cotton bollworms and aphids. From late July to early August, one to two tropical cyclones are likely to develop and form over the northwestern Pacific, facilitating the spread and outbreak of southern rust in the Huanghuai–Hai region. Overall, summer–autumn climatic conditions in southern China are not expected to pose significant adverse effects on the emergence of the fall armyworm.