Resurgence of migratory pests such as the fall armyworm.
Recently, the National Agricultural Technology Extension Center convened experts from research, educational, and extension institutions to conduct a comprehensive analysis and forecast based on pest and disease inoculum levels, crop‑planting patterns, and meteorological conditions. The 2020 national projection indicates that corn pests and diseases will affect an estimated 1.09 billion mu‑times, with insect pests accounting for 840 million mu‑times and fungal diseases for 250 million mu‑times. Migratory pests are showing a resurgence, posing a significant threat to corn growth. Specifically, the fall armyworm is migrating north earlier in the spring, with increasing populations, leading to a severe outbreak; the grass cutworm population is clearly rebounding, with localized outbreaks expected in Inner Mongolia and adjacent areas; the oriental armyworm may cause high‑density, concentrated damage in parts of northern and southwestern China; and the cotton bollworm is particularly prevalent in the Huang–Huai–Hai region, with its affected area expanding. Common pests and diseases such as the European corn borer, northern leaf blight, and southern rust are generally at near‑normal levels, while southern rust faces a risk of moderate to severe epidemics in the Huang–Huai region.
The fall armyworm has been detected across the southwestern, southern, and Jiangnan regions, as well as in the middle and lower reaches of the Yangtze River, the Jianghuai area, the Huanghuai region, North China, and the northwest corn-growing areas. There is also a potential for its migration into the spring corn‑growing regions of Northeast China. The affected area accounts for more than 80% of the total corn‑cultivation area, and all regions face the risk of concentrated damage. In the southern provinces, multiple generations occur and the damage is severe, with infested acreage potentially exceeding 100 million mu.
The corn borer is generally at a moderate level of occurrence, affecting 290 million mu‑times. Specifically, the first generation has occurred on 98 million mu‑times, with moderate infestations across most of Northeast China; the second generation has affected 110 million mu, with heavier outbreaks in localized areas of Northeast and Southwest China; and the third generation has spread over 77 million mu, with relatively severe damage in parts of the Huanghuai region. The armyworm, in its second and third generations, is generally at a moderate level, covering 68 million mu‑times, with high‑density, concentrated damage expected in some northern and southwestern areas. The cotton bollworm is also at a moderate level overall, affecting 100 million mu‑times, with heavier outbreaks in the third and fourth generations in the Huanghuai–Hai region. The grass webworm has affected 10 million mu, with the potential for heavier infestations in central and eastern Inner Mongolia, western Heilongjiang and Jilin, and localized areas of the Bashang Plateau in Hebei. Underground pests are generally at a moderate level, with localized heavier outbreaks in Northwest and Northeast China, covering 85 million mu. Aphids are at a moderate level across most of Northeast, Northwest, and Huanghuai–Hai regions, affecting 65 million mu. The two‑spotted leaf beetle is at a moderate level in most of Northeast China, as well as in parts of North China and Northwest China, covering 50 million mu. Thrips have experienced relatively severe outbreaks in localized areas of the Huanghuai region, affecting 37 million mu. The two‑spotted armyworm is generally at a mild level across the Huanghuai–Hai region, though some fields may see high‑density damage, covering 12 million mu. Spider mites are at a moderate level across most of Northwest China, with localized heavier outbreaks, affecting 26 million mu.
Large spot disease is moderately prevalent across most of Northeast China, North China, Southwest China, and Northwest China, with localized areas experiencing heavier infestations, affecting 70 million mu. Small spot disease is moderately prevalent in parts of the Huang–Huai–Hai region and in Southwest China, covering 37 million mu. Rust disease is generally at a moderate level, with localized areas in the Huang–Huai region showing heavier outbreaks, affecting 31 million mu. In addition, brown spot, Curvularia leaf spot, smut, head smut, rough dwarfism, apical rot, stem rot, ear rot, gray spot, and nematode‑induced stunting can cause varying degrees of damage in certain regions.
II. Basis for Forecasting
(1) The initial population levels of the fall armyworm and the oriental armyworm are relatively high, while the initial population level of the corn borer has declined.
1. Fall Armyworm: In 2019, the pest occurred across 26 provinces and 1,524 counties in China, with a confirmed affected area of 16.88 million mu. First, recent outbreaks of fresh‑eating corn pests have been widespread in Southwest and South China. According to statistics, in the six provinces of Yunnan, Guangdong, Hainan, Fujian, Guangxi, and Sichuan, nearly 600,000 mu of autumn‑winter‑sown fresh‑eating corn are currently infested; Yunnan, Guangdong, and Hainan account for 91%, 6%, and 2% of this area, respectively. The prevalence exceeds 70%, and in some regions the density of larvae per 100 plants is quite high: in Lincang City, Yunnan, it reaches 182 larvae; in Honghe Prefecture, Xishuangbanna, and Baoshan City, it ranges from 58 to 98 larvae; in Zhanjiang, Maoming, Yangjiang, and Shanwei counties (cities) of Guangdong, it is 40–60 larvae; in Wanning County, Hainan, it stands at 40 larvae; in Liangshan, Sichuan, at 35 larvae; and in Hechi, Chongzuo, and Beihai, Guangxi, at 16–25 larvae—far above the control threshold of 10 larvae per 100 plants. Second, live larvae (pupae) have been detected in many areas of the Yangtze River Basin in southern China. In Guizhou, Jiangxi, Hunan, Zhejiang, and Hubei, live larvae or pupae have been found in harvested corn stover or in the soil. Notably, in Dangyang, Hubei, and Wangmo, Guizhou, live young larvae were observed on volunteer corn seedlings. In several other provinces—including Guizhou, Jiangxi, Hunan, Zhejiang, and Hubei—live older-stage larvae were identified in harvested corn stover or on female ears. In Jingmen, Huanggang, and Xianning, Hubei, live pupae were unearthed in fall‑sown winter‑fallow fields, with an average density of 0.1 pupa per square meter, and up to one pupa per square meter in localized hotspots. All these locations lie south of 31°N latitude. Third, sporadic occurrences have been reported in winter wheat fields in Southwest China and other regions. With falling temperatures, most larvae in fields across the Jianghuai and Huanghuai areas have likely died from frost; however, in some locales where temperatures remain relatively mild, isolated outbreaks persist. Larvae have been detected in wheat fields across 15 counties in five provinces—Yunnan, Anhui, Henan, Sichuan, and Anhui. In Pu’er and Kunming, Yunnan, 3,000 mu of wheat are infested, with an average damage rate of 6% and 4.5 larvae per 100 plants. In Huidong County, Sichuan, the damage rate is 43%, yet field‑collected larvae are difficult to detect. In Chizhou, Anhui (30.6°N), live pupae have been found, while in Huangshan (30.2°N), field‑collected pupae can normally emerge as adults. Meanwhile, at experimental sites in Nanyang and Zhumadian, Henan, both larvae and pupae have already perished.
2. Insect sticky traps:
In 2019, the overall damage caused by the third generation of the armyworm was more severe than in the previous year, with a relatively high number of active pest sources. According to monitoring data from high-altitude light traps collected in late summer and early autumn, migrating adult moths were attracted across Northeast China, North China, the Huang-Huai region, the middle and lower reaches of the Yangtze River, the Jiangnan area, South China, and Southwest China. Notably, Changdao County in Shandong Province recorded a total of 31,820 adults from late August to the end of October—6.8 times the figure for the same period last year—while Yizhou County in Guangxi captured 1,572 adults between September and November, 2.5 times the number observed during the corresponding period of the previous year.
3. Corn borer:
According to pre-winter baseline surveys conducted across various regions, the average number of live insects per 100 tillers ranged from 30 to 48 in Heilongjiang, Tianjin, Shanxi, Shandong, Henan, Jiangsu, Yunnan, and Xinjiang, while in all other provinces it remained below 23. Compared with the previous year, the baseline levels declined significantly in most provinces; notably, in Heilongjiang, Jilin, Liaoning, Inner Mongolia, Shaanxi, Henan, Anhui, and Beijing, reductions ranged from 34% to 52%.
4. Two-spotted armyworm: In six provinces—Hebei, Henan, Shandong, Shanxi, Jiangsu, and Beijing—wintering pest sources were detected prior to the onset of winter, with an estimated infested area of 7.96 million mu, up 9.5% from the previous year. The average number of pests per mu ranged from 20 to 67 in Henan, Shandong, Shanxi, Hebei, Jiangsu, and Beijing; the highest density per square meter was 3 in Nanle, Henan; 1.2 in Wenxi, Shanxi; 0.7 in Guangping, Hebei; 2 in Yanqing, Beijing; and 1 in Feng County, Jiangsu. The baseline level of pest populations remained close to that of the previous year.
5. Grass webworm:
According to the autumn overwintering baseline survey, live cocoons overwintering were detected in Zhenglan Banner of Xilingol League in Inner Mongolia, Dalat Banner of Ordos, and Mo Banner of Hulunbuir; in Fugu County and Zizhou County of Yulin City in Shaanxi Province; and in Huinong District and Pingluo County of Shizuishan City in Ningxia. The weighted average densities of overwintering live cocoons across these three provinces/autonomous regions were 0.02, 0.05, and 0.01 per square meter, respectively, yielding an estimated total overwintering area of 1.16 million mu nationwide.
6. Diseases:
Corn diseases have been widespread year after year, with pathogen inoculum distributed across broad geographic areas. In regions such as the Huang-Huai-Hai Plain, Northwest China, and Northeast China, the practice of returning straw to the field has been vigorously promoted, with straw‑returning rates exceeding 90% in all these areas. This trend facilitates the accumulation of pathogen inoculum for a variety of diseases, including northern leaf blight, southern leaf blight, brown spot, stalk rot, common smut, and ear rot.
(2) Planting and cultivation practices are generally favorable to the occurrence of diseases and pests.
Corn is cultivated across a wide range of regions in China. In the southern areas, corn is planted year-round—through spring, summer, autumn, and winter—with uneven sowing dates and staggered planting patterns being common; fields typically harbor corn at various growth stages, providing ideal conditions for the fall armyworm to locate suitable hosts and thrive. In the major production zones of Northeast China, North China, and the Huang–Huai–Hai region, continuous corn cropping, combined with practices such as high-density planting, no‑till farming, and straw return, facilitates the accumulation of pathogen and pest inocula and promotes their establishment and damage. Moreover, the principal cultivars grown in Northeast and North China exhibit generally poor resistance to northern leaf blight, while those in the Huang–Huai–Hai region show weak resistance to brown spot and southern rust, among other diseases.
(3) Winter and spring meteorological conditions are favorable for pest overwintering and emergence.
According to monitoring and forecasts by the National Climate Center, during the winter of 2019, temperatures in South China, Southwest China, the Yangtze River region, the Huanghuai area, and Northeast China were near normal or 0.5–2°C above average, which was conducive to the occurrence and damage caused by fall armyworm and oriental armyworm in southern provinces, as well as to the overwintering of corn borers and other pests across these regions. In the spring of 2020, temperatures in Southwest China, South China, and Northeast China were 0.5–2°C higher than usual, while those in the Huanghuai and Jianghuai areas were close to normal; precipitation in the middle and lower reaches of the Yangtze River and in Northeast China was above average, favoring the emergence of corn borers and promoting the reproduction and damage caused by migratory pests such as fall armyworm and oriental armyworm.
Brown planthopper, stem borer, and other major rice pests and diseases have occurred at a severe level.
According to a joint consultation convened by the National Agricultural Technology Extension Center, bringing together pest and disease monitoring and forecasting technicians from all provinces (autonomous regions and municipalities) as well as relevant experts, and based on a comprehensive analysis of factors such as the initial pest and disease populations in rice, rice varieties, cultivation practices, and winter–spring climatic conditions, it is projected that 20… In 2020, rice diseases and pests are expected to occur at a relatively severe level (Level 4), affecting a total area of 1.2 billion mu‑times; pest infestations will cover 800 million mu‑times, while disease outbreaks will affect 400 million mu‑times. Specifically, brown planthopper, stem borer, and sheath blight are forecast to occur at a severe level (Level 4), with localized outbreaks reaching the highest severity (Level 5); rice leafroller, blast, and false smut are expected to occur at a moderate level (Level 3), with some areas experiencing severe outbreaks (Level 4); and stem borers and rice viral diseases are anticipated to occur at a mild level (Level 2).
Brown planthopper and whitebacked planthopper are expected to occur at a severe level (Level 4), affecting 300 million mu of rice fields. Specifically, the whitebacked planthopper will be severely prevalent (Level 4) in the rice-growing regions of South China and eastern Southwest China, while it will be moderately prevalent (Level 3) in the western Southwest, the Jiangnan region, and the middle and lower reaches of the Yangtze River. The brown planthopper will be severely prevalent (Level 4) in South China, Jiangnan, and the middle and lower reaches of the Yangtze River, and moderately prevalent (Level 3) in the Jianghuai rice‑growing area.
The rice leafroller is at a moderate level of occurrence (Level 3), with an affected area of 210 million mu‑times. Specifically, the Jiangnan region, eastern Southwest China, and the lower Yangtze River rice-growing areas are experiencing heavier infestations (Level 4), while South China, western Southwest China, and the Jianghuai rice-growing region are seeing moderate outbreaks (Level 3).
The rice stem borer is expected to occur at a severe level (Level 4), affecting an area of 210 million mu. Specifically, the Jiangnan region, the northern parts of Southwest China, and the rice-growing areas along the middle reaches of the Yangtze River will experience severe outbreaks (Level 4), while central and southern Hunan, northern Jiangxi, and southeastern Hubei will see localized outbreaks of great severity (Level 5). In contrast, northern South China and the Jianghuai rice-growing region are anticipated to face moderate outbreaks (Level 3).
The rice stem borer is occurring at a mild level (Level 2), with an affected area of 10 million mu. In certain rice-growing regions of South China and Southwest China, it is occurring at a moderate level (Level 3).
Other pests, including the rice stem borer, rice stem fly, and armyworm, have occurred to varying degrees in some rice-growing areas, affecting a total area of 70 million mu‑times.
Sheath blight occurred at a severe level (Level 4), affecting 260 million mu. Specifically, in South China, the Jiangnan region, the northern parts of Southwest China, and the middle and lower reaches of the Yangtze River rice-growing areas, the disease was severe (Level 4), with localized outbreaks reaching Level 5; while in southern Southwest China, the Jianghuai region, and Northeast China, it was moderately prevalent (Level 3).
Rice blast is occurring at a moderate level (Level 3), with higher-risk conditions—classified as severe (Level 4)—in the southern hilly and mountainous regions, along the Yangtze and Huai Rivers, and in the northeastern areas where the disease has long been endemic and susceptible rice varieties are widely cultivated. The affected area is estimated at 65 million mu‑times.
Rice false smut occurred at a moderate level (grade 3), with localized severe outbreaks (grade 4) in the northern Jiangnan region, along the Yangtze River, and along the Huai River, affecting an area of 35 million mu.
Rice viral diseases are expected to occur at a mild level (Level 2), affecting 5 million mu of farmland. Among these, southern rice black-streaked dwarf disease poses a moderate-to-severe epidemic risk (Level 4) in parts of South China, the southern Southwest, and certain rice-growing areas in the Jiangnan region.
Other diseases, including bacterial leaf blight, panicle rot, sesame leaf spot, and root-knot nematode disease, have occurred to varying degrees in certain rice-growing regions, affecting a total area of 35 million mu‑times.
II. Basis for Forecasting
(1) Initial pest and disease population levels
The area harboring overwintering populations of the rice stem borer before winter totals 140 million mu, with 94 million mu in the Jiangnan region, the northern parts of Southwest China, and the middle reaches of the Yangtze River. The density of live larvae per mu ranges from 1,200 to 5,700, providing a substantial base for outbreaks of moderate severity or higher. For the “two‑migratory” pests, abnormally warm temperatures during the winter and spring in their overseas source areas have favored overwintering and the accumulation of pest populations in the spring. Meanwhile, diseases such as rice sheath blight, blast, and false smut continue to build up pathogen inoculum levels in their endemic zones, resulting in high pathogen loads in the fields and laying the groundwork for outbreaks of moderate intensity or greater.
(II) Rice Varieties and Cultivation Management
Rice varieties are predominantly characterized by thick stems and large panicles, creating a microclimate of moderate temperatures and high humidity that is conducive to the occurrence and damage caused by rice diseases and pests. The major cultivated varieties generally exhibit low levels of disease resistance, with some showing reduced or lost resistance, thereby facilitating the widespread prevalence of diseases such as blast and false smut. From a cultivation‑management perspective, in the South China and Jiangnan rice‑growing regions, there is extensive intercropping of single‑ and double‑cropped rice; in the southern single‑cropping areas, uneven growth periods and numerous “bridge fields” provide abundant food resources for rice pests. An increase in fallow winter fields and tall rice stubble offer favorable overwintering habitats, promoting the accumulation of pest and pathogen reservoirs and exacerbating the incidence of diseases and pests. Imbalanced and late applications of nitrogen fertilizer result in excessive vegetative growth in the later stages of rice development, further favoring the outbreak of diseases and pests.
(3) Meteorological Conditions
According to forecasts from the National Climate Center, during the 2019 winter season (December 2019–February 2020), temperatures in major rice-producing regions were 0.5–2°C above normal, creating favorable conditions for overwintering rice pests and diseases. In the 2020 spring season (March–May), temperatures in South China and the Jiangnan rice-growing areas were 0.5–2°C higher than average, promoting the occurrence and reproduction of early-season rice planthoppers, stem borers, and other pests, as well as the outbreak and spread of rice blast and other diseases. However, precipitation in these regions was 20%–50% below normal, which exerted a certain adverse effect on the immigration of “two‑migratory” pests.
Re-emergence of major diseases and pests such as wheat scab, stripe rust, and aphids.
According to a joint analysis and consultation conducted by experts from the national plant protection system and research and educational institutions, organized by the National Agricultural Technology Center, it is projected that in 2020, major wheat diseases and pests nationwide will generally occur at a relatively severe level. The total affected area amounted to 840 million mu, with diseases accounting for 460 million mu and insect pests for 380 million mu. Fusarium head blight poses a high risk of severe or greater outbreaks in the middle and lower reaches of the Yangtze River, the Jianghuai region, and the southern Huang-Huai wheat-growing areas. Stripe rust is expected to occur at moderate to severe levels in the Jianghan Plain, the Han River basin, the southern Huang-Huai region, and parts of the southwestern and northwestern wheat-growing areas. Aphids are likely to be widespread across most of the Huang-Huai–Hai wheat-growing region, while sheath blight and powdery mildew are prevalent in the Jianghuai and high-yield wheat areas of the Huang-Huai region.
The risk of severe Fusarium head blight outbreaks is high, with an estimated affected area of 90 million mu. Preventive and control measures will need to be implemented on more than 150 million mu‑times. Specifically, widespread epidemics are expected in the middle and lower reaches of the Yangtze River and the Jianghuai wheat-growing region; moderate to severe outbreaks are anticipated in the southern Huanghuai wheat region; and other wheat-growing areas will experience moderate or mild outbreaks.
Stripe rust is expected to occur at a generally severe level, with an anticipated affected area of 60 million mu. The areas most severely affected will include much of Hubei and Shaanxi provinces, the central and southern parts of Henan province, southern Gansu province, the riverine and valley regions of Sichuan, as well as the Ili River Valley and the Tacheng Basin in Xinjiang—key wheat-growing areas.
Blast disease is expected to occur at a moderate level overall, with an estimated affected area of 120 million mu. In particular, it is likely to be more severe in Hubei, Anhui, Henan, the northern and central parts of Jiangsu, and the Jiaodong Peninsula in Shandong.
Powdery mildew is expected to occur at a moderate level overall, with an estimated affected area of 90 million mu. In particular, severe outbreaks are anticipated in northern Jiangsu and the Jianghuai region, central and northern Henan, southern Shandong, southern Shanxi, and southern Gansu.
Stem base rot is spreading and becoming more severe in the Huang-Huai-Hai wheat-growing region. Diseases such as leaf rust, root rot, take-all, and leaf blight can cause significant damage in certain wheat-growing areas.
Aphids are expected to occur at a generally severe level, with an estimated affected area of 210 million mu‑times; the areas most severely reinfested are primarily in the Huanghuaihai wheat-growing region.
Wheat spider mites are expected to occur at a moderate level overall, with an estimated affected area of 90 million mu. The pest is primarily concentrated in the wheat-growing regions of North China, the Huanghuai Plain, and the central and eastern parts of Northwest China, with particularly severe outbreaks in western Henan and northern Hubei.
During the winter and spring, the fall armyworm occurs locally in the southwestern wheat-growing region and may migrate into the middle and lower reaches of the Yangtze River, the Jianghuai Plain, and the Huanghuai wheat belt in the spring, with the potential for concentrated damage. Wheat blossom midges are primarily found in central and southern Hebei, the Guanzhong Plain of Shaanxi, and southern Henan, where localized areas may experience high-density infestations. Additionally, first-generation cutworms, cotton bollworms, wheat stem sawflies, gray planthoppers, and wheat leaf beetles can cause varying degrees of damage in certain wheat-growing regions.
II. Basis for Forecasting
(1) The initial population levels of stripe rust, aphids, and fall armyworm are relatively high.
Stripe rust emerged early, spread widely, and reached severe levels during the autumn and winter of this year. In Gansu, Ningxia, and Shaanxi—three provinces that constitute the main outbreak zone for autumn seedlings—the affected area totaled 3.103 million mu, up threefold compared with the same period last year and 63.2% higher than in 2016, marking the second most severe outbreak in the past five years. In Gansu, the affected area reached 2.309 million mu, a 210% increase year on year; average field incidence ranged from 20% to 60%, with average leaf‑infection rates between 0.01% and 0.5%. The disease was predominantly characterized by single infected leaves or localized foci, more severe than in recent years at the same time. In Ningxia, the first reports appeared on October 14, six days later than in 2018, covering 414,000 mu—an increase of 394,000 mu year on year. Average field incidence stood at 52.1%, with a spot‑incidence rate of 29.2% and an average leaf‑infection rate of 3.1%, peaking at 55.2%; severity ranged from 10% to 60%, markedly higher than usual. In Shaanxi, disease was detected across six cities and 28 counties in the Guanzhong Plain and southern regions, affecting 558,000 mu—an increase of 553,000 mu over the previous year. Occurring in scattered patches and localized clusters, the southern counties of Ningqiang, Lueyang, Mianxian, Xunyang, and Shanyang experienced the most severe outbreak since 2010. In Henan, the earliest reports emerged on November 15 in Xichuan County, Nanyang—31 days earlier than in 2016—while sporadic cases persist in Xichuan and Xixia Counties. In Hubei, disease was observed in four cities—Shiyan, Xiangyang, Jingmen, and Yichang—and 16 counties, covering 32,000 mu; multiple centers were identified, with an average severity of 30%. This represents the widest geographic spread, the greatest number of infection foci, and the highest overall intensity recorded for this period in recent years. In Sichuan, Zitong County reported its first cases on November 22, later than usual; in the eastern, western, and central parts of the province, outbreaks began in early December—15 to 54 days earlier than in 2018 and ahead of the normal seasonal onset—spanning eight prefectures and 18 counties, with a total affected area of 25,000 mu. In Yunnan, disease was detected in seven prefectures and nine counties, covering 4,000 mu; field observations revealed mostly scattered occurrences, with an average leaf‑infection rate of 0.8%, peaking at 28%. In Xinjiang, Huocheng County, Ili, reported a single infected leaf on November 18, with an average leaf‑infection rate of 0.29%.
The incidence of sheath blight in autumn seedlings is milder than at the same time in recent years. In wheat-growing regions such as the Huanghuai and North China, the affected area totals 7.48 million mu, up 8.4% year on year. In Shandong, Henan, Shanxi, and Hebei, the average incidence rates are 2.1%, 2.0%, 1.6%, and 1.0%, respectively—down 0.2 to 0.4 percentage points from the previous year. In Anhui, the average incidence rate stands at 0.1%, unchanged from the same period last year. Across most wheat-growing areas, disease severity is lower than both last year and the five-year average for this time of year.
The incidence of powdery mildew on autumn-sown wheat is milder than in recent years at this time of year. In wheat-growing regions including Southwest China, North China, the Huanghuai Plain, and Northwest China, the disease has affected 2.02 million mu, roughly unchanged from last year. In Shanxi and Shaanxi, the average percentage of infected leaves stands at 1.2% and 0.5%, respectively, while sporadic cases have been observed in southern Ningxia and western Henan, with disease severity lower than both last year and the average for the same period over the past five years.
Aphid populations in most wheat-growing regions are higher than at the same time in recent years. In the Jianghuai, Huanghuai, North China, and Northwest wheat areas, infestations cover 14 million mu, down 8.3% year-on-year and 12.0% compared with the five-year average for this period. The average number of aphids per 100 plants ranges from 2 to 10, an increase of 0.2 to 4.2 compared with the previous year. In Anhui and Shandong, densities are relatively higher, at 22.9 and 13.7 aphids per 100 plants, up 21.9 and 11.2, respectively, year on year. Pre-winter pest levels exceed both last year’s figures and the five-year average for this time of year.
In most wheat-growing regions, the pest population remains lower than in the same period over recent years. In the Jianghuai, Huanghuai, North China, and Northwest wheat areas, the infested area totals 11.8 million mu, up 38.3% year on year. The average mite density per linear foot of row is 8.0, below the five-year average of 9.6. Higher densities were observed in Shanxi, Shandong, and Hubei, at 26, 15, and 13.6 mites per foot, respectively—2.5 to 16 mites more than the five-year average.
Before winter, the fall armyworm was observed in localized wheat-growing areas of Yunnan, Sichuan, Anhui, Jiangsu, Henan, and Shandong. In Anhui, individual fields in Woyang, Qiaocheng, and Linquan counties suffered relatively severe damage. Across six provinces in Southwest and South China, the pest infested 576,000 mu of winter corn; in certain fields in Yunnan, Guangdong, Hainan, and Sichuan, the density reached 35 to 98 larvae per 100 plants, with extensive overwintering areas and high pest populations.
(2) The crop variety mix and cropping system are conducive to the occurrence of pests and diseases.
Across most of the country’s wheat-growing regions, there have been no significant changes in the variety mix, and disease and pest resistance remains low. In the eastern major wheat-producing areas, varieties generally exhibit poor rust resistance, while in the southwestern wheat belt, the dominant cultivars have lost their resistance due to the increasing prevalence of physiological race 34 of the pathogen. In the middle and lower reaches of the Yangtze River, the Jianghuai region, the Huanghuai Plain, and North China, the predominant varieties are highly susceptible to Fusarium head blight. Uneven crop development prolongs the period of susceptibility to Fusarium head blight, raising the likelihood that this vulnerable phase will coincide with prolonged spring rains and thereby increasing the risk of severe outbreaks. Moreover, dense stands and poor canopy ventilation further favor the occurrence of powdery mildew and other pests and diseases.
(3) Meteorological conditions during the winter and spring seasons are conducive to the occurrence of pests and diseases.
According to forecasts from the National Climate Center, during the winter of 2019, most of Northwest China, the Huanghuai region, and the Jianghan Plain—key wheat-growing areas—experienced above-normal precipitation and near‑normal to above‑normal temperatures, conditions that favor the overwintering and reproduction of wheat stripe rust. In spring 2020, these same regions saw above‑normal rainfall, with central Jiangsu, central Anhui, southern Henan, and much of Hubei receiving 20%–50% more precipitation than usual, thereby increasing the risk of Fusarium head blight and facilitating the spread of stripe rust. Meanwhile, in most of North China’s wheat‑growing areas, warmer-than‑normal temperatures will create favorable conditions for the occurrence and damage caused by wheat aphids.
National Forecast of the Occurrence Trends of Major Crop Pests and Diseases
On December 11–12, 2019, the National Agricultural Technology Center organized representatives from the national plant protection system and research and educational institutions. Leading experts convened to analyze and discuss the 2020 national trends in the occurrence of major crop pests and diseases. Taking into account factors such as baseline pest and disease levels, crop distribution, cropping systems, and climate trends, it is projected that the overall incidence of major crop pests and diseases in China in 2020 will be more severe than in 2019, with a cumulative affected area of approximately 4.5 billion mu‑times. Among these, the fall armyworm is expected to migrate north earlier, across a broader geographic range, and cause more serious damage; its resurgence is pronounced, making the situation particularly grave. There is also a high risk of recurrence for epidemic diseases such as wheat scab and stripe rust. Major pests and diseases—including rice planthoppers, stem borers, wheat aphids, and cotton bollworms—are likely to occur at relatively severe levels. The oriental armyworm may infest crops at high densities in certain areas of northern and southwestern China. Meanwhile, the grass webworm population shows a clear upward trend, with the potential for localized outbreaks.
I. Rice Diseases and Pests
Brown planthopper is expected to occur at a severe level, affecting 300 million mu‑times. Specifically, the whitebacked planthopper will be severely prevalent in the rice-growing areas of South China and eastern Southwest China, while it will be moderately prevalent in the western Southwest, the Jiangnan region, and the middle and lower reaches of the Yangtze River. The brown planthopper will be severely prevalent in South China, Jiangnan, and the middle and lower Yangtze River regions, with moderate prevalence in the Jianghuai rice‑growing area. The rice leafroller is forecast to occur at a moderate level, covering 210 million mu‑times. It will be severely prevalent in Jiangnan, eastern Southwest China, and the lower Yangtze River region, while it will be moderately prevalent in South China, western Southwest China, and the Jianghuai rice‑growing area. The stem borer is expected to occur at a severe level, affecting 210 million mu‑times. Severe outbreaks are anticipated in Jiangnan, northern Southwest China, and the river‑adjacent rice‑growing areas along the middle Yangtze; localized large outbreaks are possible in central and southern Hunan, northern Hunan, northern Jiangxi, and southeastern Hubei; moderate outbreaks are expected in northern South China and the Jianghuai rice‑growing area.
Rice blast is occurring at a moderate level, with an affected area of 65 million mu‑times. In particular, the old epidemic areas in the southern hilly and mountainous regions, along the Yangtze and Huai Rivers, and in Northeast China, as well as areas where susceptible rice varieties are cultivated, face a high risk of severe outbreaks.
II. Wheat Diseases and Pests
The risk of severe epidemics of Fusarium head blight is high, with an affected area of 90 million mu; preventive and control measures will need to be applied across more than 150 million mu‑times. Specifically, the middle and lower reaches of the Yangtze River and the Jianghuai wheat region are expected to experience major outbreaks, while the southern Huanghuai wheat region will see moderately severe outbreaks, and other wheat-growing areas will face moderate or mild outbreaks. Stripe rust is generally expected to occur at a relatively severe level, affecting 60 million mu; the main areas of recurrent severe outbreaks include most of Hubei and Shaanxi provinces, the central and southern parts of Henan, southern Gansu, the riverine and valley regions of Sichuan, as well as the Ili River Valley and the Tacheng Basin in Xinjiang.
Aphids have generally been a serious pest, with an affected area of 210 million mu‑times; the areas experiencing severe outbreaks are primarily in the Huanghuaihai wheat-growing region.
III. Corn Diseases and Pests
The fall armyworm has been detected across major corn‑producing regions, including Southwest China, South China, the Jiangnan area, the middle and lower reaches of the Yangtze River, the Jianghuai region, the Huanghuai Plain, North China, and Northwest China, with the potential for migration into the spring corn belt of Northeast China. These infested areas account for more than 80% of China’s total corn‑cultivation acreage, with over 100 million mu affected. All regions face the risk of concentrated damage, and southern provinces experience multiple generations and severe outbreaks. The corn borer is generally at a moderate level of occurrence, affecting 290 million mu in total. Specifically, the first generation infests 98 million mu, with overall light to moderate damage and localized moderate outbreaks in Northeast China; the second generation affects 110 million mu, with locally heavy outbreaks in parts of Northeast and Southwest China; and the third generation covers 77 million mu, with some areas in the Huanghuai region experiencing heavy infestations.
Large-spot disease is occurring at moderate levels across most of Northeast China, North China, Southwest China, and Northwest China, with localized areas experiencing heavier infestations, affecting a total area of 70 million mu.
IV. Potato Diseases and Pests
Late blight of potato poses a high risk of severe outbreaks across most of Southwest China, northern Northeast China, northern North China, and eastern Northwest China, with an affected area of 28 million mu.
In addition to corn, the fall armyworm will also infest a variety of crops, including wheat, sugarcane, and sorghum. During the winter and spring, it poses a significant threat to wheat growth in the southwestern region, the middle and lower reaches of the Yangtze River, and the Jianghuai wheat‑growing area, with localized outbreaks potentially becoming severe. The second and third generations of the common cutworm are expected to occur at moderate levels, affecting 70 million mu‑times; high‑density, concentrated damage may occur in parts of northern and southwestern China. The cotton bollworm is forecast to be at a moderate level overall, with an affected area of 100 million mu‑times, while the third and fourth generations are likely to be heavier in the Huang‑Huai‑Hai region. The grass webworm population is showing a clear upward trend, with an affected area of 10 million mu; there is a potential for moderately severe outbreaks in central and eastern Inner Mongolia, western Heilongjiang and Jilin, and parts of the Bashang Plateau in Hebei.
Source: National Agricultural Technology Extension Service Center |
