At present, diseases and pests in the late-season double-cropping rice are generally at moderate levels; in some areas, vigilance is required to prevent outbreaks of brown planthoppers that could lead to severe damage.

Release Date:

2018-10-09

　At present, late-season double-cropping rice in South China and the Jiangnan region is in the booting–heading stage. Overall pest and disease pressure is moderate; however, brown planthoppers are increasing rapidly in the eastern Jiangnan rice‑growing areas, stem borers are slightly above average in South China, and two‑banded stem borers are significantly more abundant than usual in the Jiangnan region. Sheath blight is widespread, blast on the panicle neck is beginning to appear, and rice viral and bacterial diseases are causing relatively severe damage in localized areas. In the next phase, rainfall in eastern Jiangnan is expected to exceed the long-term average for this time of year, creating favorable conditions for the return and settlement of migratory pests as well as the outbreak and spread of other rice pests and diseases. In particular, areas in northern Fujian with high initial populations of brown planthoppers should remain vigilant against potential outbreaks that could lead to widespread crop losses.
　　Rice pest infestation
　　1 Rice planthopper
　　Brown planthoppers are occurring at moderate levels in the rice-growing regions of South China and the Yangtze River Basin, with a current affected area of 35.22 million mu, up 1.6% year on year. Since early September, monitoring in these regions has detected a return‑migration peak, with the brown planthopper accounting for the majority of migrating species; overall migration volumes have declined by 10.9% compared with the same period last year. According to local surveys, pest densities in fields are lower than during the same period last year, with typical counts ranging from 100 to 600 insects per hundred tillers. In eastern South China and along the coastal areas, densities are higher, at 800 to 1,300 insects per hundred tillers, and in some localized plots they reach as high as 3,000 to 6,000 insects per hundred tillers; in individual fields in You County, Hunan, peak densities have even exceeded 10,000 insects per hundred tillers. Notably, insect populations in Fujian have been rising rapidly lately: in Nanping, late‑season double-cropping rice fields typically harbor 1,500 to 2,200 insects per hundred tillers, with some reaching as high as 2,800, and in certain plots the infestation has already become so severe that the foliage appears “pierced through.”
　　2 Rice leafroller
　　The rice leafroller has been generally mild in the South China and Jiangnan rice‑growing regions, with a current infested area of 19.14 million mu, down 2.0% year on year. Since early September, monitoring across various localities has detected a migratory peak; field moth densities typically range from 50 to 500 per mu, with localized peaks in South China reaching 1,000 to 3,000 per mu. Larval populations are comparable to those of the same period last year, slightly higher in South China, with typical densities of 1,000 to 8,000 per mu and localized outbreaks as high as 10,000 to 40,000 per mu. Field leaf‑rolling rates generally stand at 0.1% to 3%, with higher levels of 4% to 7%, and in some fields in Anyuan, Jiangxi, reaching as high as 12%.
　　3 Rice stem borer
　　The rice stem borer is occurring at moderate to severe levels in the rice-growing regions of southern Jiangnan, with a current affected area of 16.05 million mu, up 6.0% year on year. Monitoring indicates that these regions have entered the peak egg‑hatching period for the fourth generation; field pest populations are higher than usual for this time of year, with larval densities generally ranging from 500 to 2,500 per mu, and in central and eastern Hunan reaching 3,000 to 8,000 per mu, with some localized fields exceeding 30,000 per mu. Damage caused by infestation results in a deadheart rate typically between 0.1% and 1.2%, with higher rates of 3.8% to 8.6% in certain areas.
　　Rice diseases
　　1. Sheath Blight
　　Blast disease is generally severe in the rice-growing regions of South China and the Yangtze River Basin, with a current affected area of 37.7 million mu, down 4.4% year on year. At present, the disease is in its vertical expansion phase, with disease‑plant rates typically ranging from 4% to 27%, and in some cases reaching 35% to 60%; disease‑clump rates generally stand at 15% to 40%, with higher levels of 45% to 78%, and in localized fields in southern Jiangxi—such as Ji’an and Yihuang—reaching as high as 100%.
　　2 Rice blast disease
　　Rice blast has been generally mild in the late‑rice growing regions of South China and the Jiangnan area, with a current affected area of 2.05 million mu, down 12.7% year on year. Leaf blast is widespread in the fields, with disease‑leaf rates typically ranging from 0.5% to 5%; in parts of northeastern, central, and western Guangxi, peak rates reach 11% to 21%. Neck blast is progressively appearing on late‑season double‑cropped rice in the Jiangnan region, with diseased panicle rates generally between 0.1% and 1.1%, and in some localized plots in Yanshan, Jiangxi, reaching as high as 9%.
　　3 Southern Rice Black-Streaked Dwarf Disease
　　Southern rice black-streaked dwarf disease has occurred at low levels in the late‑rice growing regions of South China and the Jiangnan area, with some localized outbreaks being more severe. The current affected area stands at 240,000 mu, a 62.9% decrease compared with the same period last year. Field incidence rates generally range from 0.1% to 2.7%, with localized peaks of 4% to 23% in southern, eastern, and central Guangxi. In western Guangdong, certain fields exhibit relatively high disease‑affected plant rates; for example, Qingcheng District, a newly reported outbreak area this year, has seen disease‑affected plant rates as high as 40% to 50% in some plots.
　　4 Other Diseases
　　Orange leaf disease is relatively severe in certain rice-growing areas of South China, with infected tiller rates generally ranging from 0.02% to 15%, and in some cases reaching 20% to 40%; infected leaf rates typically fall between 0.01% and 0.5%, with higher incidences of 2% to 10%. Bacterial diseases of rice have expanded in their geographic range compared with the same period last year across South China and the Jiangnan rice region, but overall incidence remains mild; localized outbreaks are more severe in southern Guangxi and western Guangdong.
　　According to forecasts from the National Meteorological Center, eastern Jiangnan is expected to experience above-normal rainfall over the next 10 days, creating favorable conditions for the return and settlement of rice planthoppers and stem borers, as well as for the further development and damage caused by pests and diseases. In particular, in northern Fujian—where initial populations of rice planthoppers are already high—vigilance is advised to prevent outbreaks that could escalate into full-blown disasters. Local authorities are urged to attach great importance to this issue, tailor control measures to local conditions, and ensure thorough monitoring and timely treatment. As long as autumn grain remains unharvested, preventive efforts must remain unwavering, with all possible measures mobilized to secure a bountiful autumn harvest.