Current Dynamics of Diseases and Pests Affecting Mid- to Late-Season Rice

　　At present, mid-season rice in South China and the Yangtze River region, as well as single-season rice in Southwest and Northeast China, are in the booting to heading stages; late-season rice in South China and the Yangtze River region is at the green-up to tillering stage; and single-season rice in the middle and lower reaches of the Yangtze River is in the tillering to jointing stage. Overall, rice diseases and pests are expected to be mild to moderate. Compared with the same period last year, brown planthopper populations are higher than last year in South China, the mid-season rice areas of the Yangtze River region, and the single-season rice areas of Southwest China; stem borer populations are also higher than last year in the northern Southwest and the Yangtze River region, posing a greater risk than in the previous year. According to forecasts from the National Meteorological Center, the coming period will see frequent showers in the rice-growing regions of Southwest and Northeast China, which could favor the occurrence and spread of rice diseases and pests, particularly blast disease of the panicle neck.
　　Rice planthopper
　　Brown planthoppers have been occurring at light to moderate levels across southern rice-growing regions, with localized areas experiencing heavier infestations. The current affected area totals 71.02 million mu‑times, roughly unchanged from the same period last year. Since mid-July, two peak trapping periods have been observed: one from July 14–17 and another from July 23–27, in South China, eastern Southwest China, and southern Jiangnan. Notably, on July 24, Yiliang in Yunnan and Xinyi in Guangdong each recorded over 10,000 insects caught by a single trap in a single day. Overall trap catches were down 22.4% year-on-year; whitebacked planthopper populations remained similar to last year, while brown planthopper numbers declined by 69.1%. According to local monitoring, in South China, mid-season rice areas of Jiangnan, and single-cropping rice regions of Southwest China, the average pest density is typically 200–900 insects per 100 plants, with some fields reaching 1,000–2,000. In central Chongqing, nine districts and counties reported peak densities exceeding 10,000 insects per 100 plants in mid-July, and in parts of Dianjiang and Liangping, “tunneling” damage has already appeared in some paddy fields. Following effective control measures, the city’s current average pest density has fallen to 557 insects per 100 plants. Compared with the same period last year, field populations remain elevated, with Chongqing, Sichuan, Yunnan, and Hunan reporting increases of 65.2%, 55.5%, 26.7%, and 6.3%, respectively. In South China, late-season rice areas of Jiangnan, and single-cropping rice regions along the middle and lower Yangtze River, pest densities generally stay below 150 insects per 100 plants, though some fields reach 250–650. In Hubei’s Xiantao, isolated poorly managed plots have exceeded 10,000 insects per 100 plants. Overall, field populations are lower than last year, but localized areas along the middle Yangtze show higher-than-normal densities—Hubei’s figures are 2.4 times those of the same period last year, while Anhui’s have risen by 24.6% year-on-year.
　　Rice leafroller
　　In the southern rice‑growing regions, the rice leafroller has generally been at a light to moderate level of occurrence. To date, the affected area totals 51.57 million mu‑times, close to the level of the same period last year. In late July, distinct peaks in adult rice leafroller moths were detected in the middle and lower reaches of the Yangtze River, with moth populations 5 to 10 times those of the previous year. Field densities ranged from 50 to 400 moths per mu, reaching 500 to 1,000 in areas along Lake Taihu and the Yangtze River, and locally soaring as high as 13,000 in certain fields in Tongcheng, Hubei. Affected by sustained high temperatures, larval populations in the mid‑season rice areas of South China and Jiangnan, as well as in the single‑cropping rice areas of Southwest China, have declined somewhat, with field densities typically between 1,000 and 3,000 larvae per mu, and in some cases 5,000 to 10,000. In localized fields in southern Hunan and northern Guangxi, densities exceeded 10,000 larvae per mu. By contrast, larval numbers in the late‑season rice areas of Jiangnan and the single‑cropping rice regions of the middle and lower Yangtze River have risen markedly, ranging from 30 to 500 larvae per mu, with higher counts of 800 to 1,000. Overall, the extent of damage remains relatively mild: in South China, Jiangnan mid‑season rice, and Southwest single‑cropping rice, leaf‑rolling rates generally stand at 2% to 6%, with higher levels of 8% to 13%, and in some local fields in Qianjiang, Chongqing, reaching as high as 46.7%; in Jiangnan late‑season rice and the middle and lower Yangtze River single‑cropping rice, leaf‑rolling rates are typically below 2%.
　　Two-brooded stem borer
　　The rice stem borer is generally at moderate levels of occurrence across the Jiangnan, Southwest, middle and lower reaches of the Yangtze River, and the Jianghuai rice-growing regions. To date, it has affected 57.86 million mu‑times, a 2.8% decrease compared with the same period last year. In the northern Southwest and the Jiangnan rice areas, pest populations are higher than in the corresponding period last year, with larval densities typically ranging from 450 to 1,400 per mu, and in some cases reaching 2,000 to 5,000 per mu; in localized fields in Rui’an, Zhejiang, densities have soared as high as 50,000 per mu. Field damage has resulted in a dead‑sheath rate of 1% to 3%, with peak rates of 16% to 30%; the dead‑heart rate stands at 0.7% to 1.2%, with higher values of 4% to 7%, and in certain fields in Huangzhou, Hubei, it has reached as high as 23%.
　　Sheath blight
　　Sheath blight is occurring at moderate levels in the major rice‑producing regions, with a current affected area of 74.8 million mu, down 4.3% year on year. Field disease severity is lower than during the same period last year: in South China, the middle rice‑growing areas of the Yangtze River Basin, and the single‑cropping rice areas of Southwest China, the incidence of infected plants generally ranges from 3% to 11%, with higher rates of 15% to 20%; the incidence of infected tillers is typically 8% to 15%, reaching 30% to 40% in some cases. In South China, the late‑season rice areas of the Yangtze River Basin, and the single‑cropping rice regions along the middle and lower reaches of the Yangtze, sheath blight has entered a phase of lateral spread, with the incidence of infected plants generally between 1% and 5%, and up to 5% to 10% in localized hotspots; the incidence of infected tillers is usually 7% to 14%, with peaks of 16% to 30%.
　　Rice blast disease
　　Rice blast has generally been mild, with a current affected area of 10.93 million mu‑times, down 10.7% year on year. In the South China and middle‑rice regions of Jiangnan, as well as in the single‑crop rice areas of Southwest and Northeast China, the incidence of blast—measured as the percentage of infected leaves—typically ranges from 0.1% to 2.5%, with higher levels reaching 5% to 20%; the percentage of infected panicles is usually below 1%, though it can be as high as 3% to 4.6% in the Southwest. For late‑season rice in South China and Jiangnan, and for single‑crop rice in the middle and lower reaches of the Yangtze River, the rate of infected leaves is generally less than 1%, although in some poorly managed fields in Hong’an, Hubei, it has reached as high as 73.5%.
　　Future Trends and Recommendations
　　According to forecasts from the National Meteorological Center, over the next 10 days, the rice-growing regions of Southwest and Northeast China will experience frequent showers, with rainfall 30% to 80% above normal for this time of year. This weather pattern is likely to favor the occurrence and spread of rice diseases and pests, particularly blast disease of the panicle neck, as well as the reproduction and proliferation of “two‑migration” pests in the Southwest rice areas. All localities are urged to strengthen monitoring, maintain a comprehensive grasp of pest and disease dynamics, issue timely and accurate pest and disease advisories, and implement effective guidance on prevention and control measures.

Source: Pest and Disease Monitoring and Forecasting Division, National Agricultural Technology Extension Service Center