Severe outbreaks are expected: corn pests and diseases are projected to affect 840 million mu, while rice pests and diseases are forecast to impact 920 million mu. Special vigilance is required for these threats.

Release Date:

2021-07-27

Corn What is the trend of pest and disease outbreaks in the mid-to-late growth stages? And how are pests and diseases developing in mid- to late-season rice? Recently, technical staff from plant protection agencies and relevant experts, based on the current baseline levels of pest and disease occurrence, Corn , the regional distribution and cropping systems of rice, combined with a comprehensive analysis of future weather conditions, for Corn and forecast the future trends of rice diseases and pests.
Corn
Expected this year Corn In the mid-to-late growth stages, pest and disease incidence was generally severe, exceeding the long-term average and approaching last year’s levels. Migratory pests such as the fall armyworm, third-generation cutworms, second-generation grass webworm, and cotton bollworm have affected… Corn The production threat is significant, Corn Sesame stem borers, southern blight, and brown spot are widespread, with a potential for a severe resurgence of southern rust; the peak period of damage occurs in northern regions. Corn In most growing regions, planting occurs from late July to late August; in southern areas… Corn The planting season is sustainable until the end of October.
Trend of occurrence
Expected nationwide Corn In the mid-to-late stages, pest and disease outbreaks occurred on 840 million mu of farmland, with pests affecting 570 million mu and diseases affecting 270 million mu—up 2%, 2%, and 4% year on year, respectively.
The fall armyworm primarily damages summer- and autumn-sown crops in Southwest China, South China, and the Jiangnan region. Corn In most regions, the infestation is more severe than last year. In key breeding areas such as Yunnan, Guangxi, and Guangdong, outbreaks are expected to be heavy, with localized severe outbreaks; in the Jiangnan region and the middle and lower reaches of the Yangtze River, outbreaks will be moderate, with some areas experiencing heavier-than-average infestations; in the Huanghuai and Northwest regions, outbreaks will be relatively mild; and in North China, isolated patches may see limited occurrences. In southern Northeast China, there is a high likelihood of adult moths migrating into the area and of sporadic larval infestations. Overall, the nationwide affected area is projected to exceed 20 million mu.
Overall, the three generations of the armyworm are expected to occur at moderate levels. High-density, localized outbreaks are likely in the northwest, northeast, North China, the Huang–Huai region, and the southwest, affecting 35 million mu. The second generation of the grass webworm is highly likely to cause severe damage in Inner Mongolia and adjacent areas, with adult emergence and larval activity covering 10 million mu. The third and fourth generations of the cotton bollworm are forecast to occur at moderate levels in the Huang–Huai–Hai region, spanning 65 million mu. Corn Stem borers are moderately prevalent across most of North China, the Huanghuai region, and Northwest China, with cumulative infestations affecting 200 million mu. Aphids are moderately prevalent in much of Northeast, North, and Northwest China, covering an area of 60 million mu. Spider mites and the two-spotted leaf beetle are moderately prevalent in certain areas of the Northwest and North China, each affecting 25 million mu. Grasshoppers may cause some damage in parts of the arid regions of northern China, with an affected area of 10 million mu.
Large spot disease is expected to occur severely in Northeast China, moderately in northern North China, eastern Northwest China, and localized areas of Southwest China, affecting 68 million mu; southern rust has a high likelihood of severe epidemics in the Huanghuaihai region, with an affected area of 30 million mu; small spot disease will occur at moderate levels across central and southern Huanghuai and most of Southwest China, covering 42 million mu; brown spot disease will be moderate in the Huanghuaihai region, affecting 33 million mu; and northern anthracnose will occur at moderate levels in northern Northeast China, impacting 10 million mu. In addition, diseases such as Curvularia leaf spot, sheath blight, and gray leaf spot are also likely to cause some damage.
Forecast Basis
(1) High baseline pest population
As of July 14, the fall armyworm has infested a cumulative 12.14 million mu across 917 counties and county-level cities in 20 provinces, an 11% year-on-year increase. Average pest densities per 100 plants range from 14 in Yunnan to 5–10 in other southwestern and South China provinces, 2–5 in the Jiangnan and Yangtze River Basin regions, and less than 1 in the Huanghuai and Northwest areas. The highest densities—50–100 larvae per 100 plants—are reported in Qiubei, Jiangcheng, and Menghai in Yunnan; Huicheng, Gaozhou, and Yangdong in Guangdong; Haicheng and Pingguo in Guangxi; Xishui in Guizhou; Huidong and Zhaohua District in Sichuan; Zhouning, Xianyou, and Shouning in Fujian; Qingyuan and Wenling in Zhejiang; Caishang in Jiangxi; Laifeng and Duodao in Hubei; and Chenxi and Hengdong in Hunan. Even higher densities—100–200 larvae per 100 plants—are observed in Jinghong, Linxiang, Zhenyuan, Tengchong, and Lancang in Yunnan; Xingbin and Tian’e in Guangxi; Muli, Butuo, and Ningnan in Sichuan; and Tongdao in Hunan.
As of July 14, the second generation of armyworms has infested 35 million mu across Northwest, Huanghuai, North China, Northeast China, and Southwest China—15% more than the same period last year—and the severity of the outbreak exceeds both last year’s levels and the long-term average. Specifically, areas with 10–30 larvae per 100 plants account for 10 million mu, while heavily re‑infested areas with more than 30 larvae per 100 plants cover 2.5 million mu. In localized regions—including central and northern Ningxia, western Inner Mongolia, central Shanxi, northern Shaanxi, and central Gansu—high‑density, concentrated damage has been observed in certain fields. At present, the second‑generation armyworm infestation has largely subsided; residual densities in Ningxia, Inner Mongolia, and Yunnan range from 3 to 5 larvae per square meter, while in most other areas they remain below 1 larva per square meter.
In the main outbreak areas of Inner Mongolia, Shanxi, Hebei, and other regions, the overwintering generation of the grass webworm has emerged across 4 million mu, while the first-generation larvae have infested 1 million mu, including 860,000 mu in agricultural fields. The most severe outbreaks are concentrated in central Inner Mongolia and northern Shanxi.
Corn The population density of the rice stem borer continues to decline year by year. The average number of larvae per 100 plants is below 13 in most areas, with 16 in Liaoning and 28 and 35 in Yunnan and Guizhou, respectively.
(2) Corn The growth period and cultivation practices are conducive to the occurrence of pests and diseases.
At present, in the Huang-Huai-Hai region, the Northwest, and other areas Corn Most are in the trumpet‑mouth stage; the Southwest is from the seedling stage to flowering; the South… Corn Intercropping, summer–autumn season Corn The growing periods vary, but all are suitable for fall armyworm feeding and damage. Northern regions. Corn When crops are planted in contiguous blocks, the resulting tall stands and dense canopy create favorable conditions for the occurrence and damage caused by pests and diseases. In particular, fields with lax management and abundant weeds provide ideal conditions for the concentrated oviposition and subsequent damage inflicted by the oriental armyworm and the common cutworm. Meanwhile, across different regions… Corn Diseases such as large spot and brown spot have occurred year after year, and the high proportion of straw returned to the field further promotes the accumulation of pathogenic fungi.
(3) Meteorological conditions across most regions Corn Favorable conditions for the occurrence of diseases and pests
According to forecasts from the National Climate Center, during July and August, the central and eastern parts of Northwest China, most of Inner Mongolia, North China, Northeast China, the Huanghuai region, and southern South China are expected to experience above-normal precipitation, which will be conducive to the occurrence of fall armyworm, oriental armyworm, and grass webworm, and… Corn Disease outbreaks: In most of Xinjiang, southern Huanghuai, and the Jianghuai region, temperatures are 1–2°C above normal, with precipitation at or below average, creating favorable conditions for the occurrence and damage caused by drought‑tolerant pests such as the cotton bollworm and aphids. In the second half of the year, 6–8 typhoons are expected to make landfall in China, near or slightly above the long-term average, which will facilitate the spread and epidemic development of southern rust in the Huanghuai–Hai region and further promote the northward migration of the fall armyworm.
Rice
It is projected that in 2021, major rice diseases and pests will occur at a generally severe level, affecting a total area of 920 million mu‑times. Specifically, pest outbreaks are expected to cover 630 million mu‑times, while disease outbreaks will affect 290 million mu‑times. Among these, brown planthopper and sheath blight are anticipated to be severe; stem borer, two-brooded stem borer, and rice blast are expected to range from moderate to severe; rice false smut is forecast to be moderate; and southern rice black-streaked dwarf disease is expected to be mild.
Trend of occurrence
Rice pest infestation
Rice planthoppers have occurred at a severe level, with a nationwide infested area of 270 million mu‑times. Specifically, the whitebacked planthopper has been severely prevalent in eastern Southwest China and the Jianghan Plain, while it has been moderately prevalent across most of the Southwest, the middle and lower reaches of the Yangtze River, South China, the Jiangnan region, and the Jianghuai rice‑growing areas. The brown planthopper has been severely prevalent in eastern South China, most of the Southwest, the Jiangnan region, and the middle and lower reaches of the Yangtze River, and moderately prevalent in much of South China, eastern Southwest China, and the Jianghuai rice‑growing areas.
The rice leafroller is expected to occur at a severe level in the western Jiangnan region and along the Yangtze River and lakes in the middle and lower reaches; at a moderate level across most of Jiangnan, the middle and lower Yangtze River basin, eastern Southwest China, and much of South China; with a nationwide infested area of 160 million mu.
The rice stem borer is severely prevalent in the western part of the Jiangnan region, while it occurs at moderate levels in the northwestern and southwestern regions, eastern South China, eastern Jiangnan, the middle and lower reaches of the Yangtze River, the Jianghuai area, and the central and southern parts of Northeast China; the total affected area nationwide amounts to 130 million mu.
Other pests, including the brown planthopper, stem borer, rice stem borer, rice leaf miner, armyworm, and Taiwan rice stem borer, have occurred to varying degrees in some rice-growing areas, with a total affected area of 69 million mu nationwide.
Rice diseases
Sheath blight is expected to occur at a severe level across most of South China, eastern Southwest China, the Jiangnan region, and the middle and lower reaches of the Yangtze River rice‑growing areas, while it will be moderate in eastern South China, much of the Southwest, and most of Northeast China; the nationwide affected area is estimated at 180 million mu‑times. Rice blast poses a high risk of severe outbreaks in the hilly and mountainous regions of Southwest and Jiangnan China and in the Northeast rice‑growing areas, with moderate incidence elsewhere across most rice‑producing regions; the national affected area is projected at 56 million mu‑times.
Rice false smut is generally occurring at a moderate level, with a risk of more severe outbreaks during the heading and flowering stages if prolonged rainy weather persists; the nationwide affected area totals 38 million mu. Southern rice black-streaked dwarf disease is generally mild, though localized areas in western Guangxi, southwestern Guangdong, and central-southern Hunan are experiencing moderate incidence; the affected area stands at 1 million mu.
Rice bacterial leaf blight, panicle rot, sesame leaf spot, root-knot nematode disease, and other diseases have occurred to varying degrees in some rice-growing regions, with a total affected area of 15 million mu nationwide.
Basis of the forecast
(1) The baseline populations of “two‑migration” pests and other disease‑and‑pest organisms meet or exceed the conditions for moderate to severe outbreaks.
Currently, in most rice-growing areas of South China, the Jiangnan region, and the Southwest, the rice planthopper population averages 300–1100 insects per 100 plants; in eastern Southwest China and central Jiangnan, local peaks reach 60,000–100,000 insects per 100 plants. In the middle and lower reaches of the Yangtze River and the Jianghuai region, the average is 100–300 insects per 100 plants, with localized peaks as high as 4,000 in Shanghai. For the rice leafroller, field larval densities remain low: 5,000 in Hunan, 2,700 in Guangxi, and 1,200 in Chongqing, while other regions generally stay below 500 larvae per 100 plants; however, in parts of west-central Hunan and central Guizhou, some fields exceed 100,000 larvae per 100 plants. The rice stem borer shows moderate to severe infestations in northern Southwest China, eastern South China, and the middle and lower Yangtze River rice‑growing areas, with 250–450 larvae per mu; yet in Hunan, the average climbs to 3,500 larvae per mu, surpassing the threshold for a major outbreak (1,000 larvae per mu). Rice blast continues to occur widely across numerous locations, with susceptible varieties still accounting for a significant share of plantings. Sheath blight remains a persistent problem, with ample pathogen inoculum present in the fields.
(2) Host crops and field ecological conditions are conducive to the occurrence of pests and diseases.
In China’s South China and Jiangnan rice-growing regions, the extensive co‑cultivation of single‑ and double‑cropped rice facilitates the sequential damage caused by migratory rice pests and stem borers. In the Southwest and the middle–lower reaches of the Yangtze River, the uneven maturity of single‑cropped rice increases the likelihood that susceptible growth stages coincide with prolonged cloudy and rainy weather, thereby promoting the spread of climate‑dependent diseases such as blast and false smut. Across these areas, mid‑ to late‑season rice varieties are predominantly high‑quality; however, the resistance levels of the main cultivars remain relatively low, with some varieties experiencing a decline or loss of resistance. Moreover, under intensive cultivation practices characterized by high water and fertilizer inputs, favorable host nutrition and dense canopy conditions further favor the occurrence and epidemic development of rice diseases and pests.
(3) Meteorological conditions are generally favorable for the occurrence of epidemic diseases and the northward migration of “two‑transferred” pests.
According to forecasts from the National Meteorological Center, during this year’s peak summer months (July–August), temperatures across China are expected to be generally above normal. Increased rainfall is anticipated in Northeast China, eastern Jianghuai, northeastern Jiangnan, the eastern and northern parts of Southwest China, most of the Jianghan region, and southern South China, creating favorable conditions for the outbreak and spread of rice diseases such as blast, sheath blight, and false smut, with a heightened risk of localized, sudden epidemics. In contrast, southern Southwest China, South China, Jiangnan, and much of the middle and lower reaches of the Yangtze River are likely to experience below-normal precipitation. Meanwhile, areas including Jianghuai, Jianghan, and Jiangnan are expected to see an above‑normal number of days with high temperatures (daily maximum ≥35°C), leading to intermittent heatwaves. These conditions will exert some suppressive effects on the population dynamics of “two‑migration” pests. However, 6–8 typhoons are forecast to make landfall in or significantly impact China in the second half of the year—near the long-term average or slightly above—potentially including northward‑moving systems that could markedly affect East China and regions further north, thereby facilitating the northward migration and subsequent damage caused by these pests.