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 at the booting to heading stage; late-season rice in South China and the Yangtze River region is in the regreening to tillering stage; and single-season rice in the middle and lower reaches of the Yangtze River is at 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 parts of Southwest China and the Yangtze River region, with pest densities exceeding those of the previous year. According to forecasts from the National Meteorological Center, the next phase will see frequent showers in the rice-growing regions of Southwest and Northeast China, which will 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 mild 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 in South China, eastern Southwest China, and southern Jiangnan: July 14–17 and July 23–27. Notably, on July 24, Yiliang in Yunnan and Xinyi in Guangdong each recorded over 10,000 insects caught by a single light 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 regional monitoring, in South China, central Jiangnan’s medium‑season rice areas, and the single‑cropping rice zones of Southwest China, planthopper densities generally range from 200 to 900 per 100 plants, with some fields reaching 1,000 to 2,000. In central Chongqing, nine districts and counties reported peak densities exceeding 10,000 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 average density has now fallen to 557 per 100 plants. Compared with the same period last year, field populations remain elevated, with Chongqing, Sichuan, Yunnan, and Hunan showing increases of 65.2%, 55.5%, 26.7%, and 6.3%, respectively. In South China, late‑season rice areas of Jiangnan, and the single‑cropping rice zones along the middle and lower Yangtze River, planthopper densities are typically below 150 per 100 plants, with higher counts ranging from 250 to 650; in Xiantao, Hubei, isolated poorly managed plots have exceeded 10,000 per 100 plants. Overall, field populations remain lower than last year, though localized areas along the middle Yangtze show higher densities—Hubei’s levels are 2.4 times those of the same period last year, and Anhui’s have risen by 24.6% year on year.
　　Rice leafroller
　　In the southern rice‑growing regions, the rice leafroller has been generally mild to moderately prevalent, with a current affected area of 51.57 million mu—close to the level of the same period last year. In late July, distinct peaks in adult moth populations were recorded in the middle and lower reaches of the Yangtze River, with moth counts 5 to 10 times higher than during the same period last year. Field densities ranged from 50 to 400 moths per mu, reaching 500 to 1,000 in areas along Lake Tai and along the riverbanks, and locally soaring as high as 13,000 moths per mu in Tongcheng, Hubei. Affected by sustained high temperatures, larval populations in South China, the mid‑season rice areas of Jiangnan, and the single‑cropping rice regions 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 late‑season rice areas of Jiangnan and in the single‑cropping rice zones of the middle and lower Yangtze River have risen markedly, ranging from 30 to 500 larvae per mu, with peak densities of 800 to 1,000. Overall, damage levels remain relatively light: in South China, Jiangnan’s mid‑season rice, and Southwest China’s single‑cropping rice, leaf‑rolling rates generally range from 2% to 6%, with higher rates of 8% to 13%, and locally peaking at 46.7% in Qianjiang, Chongqing; in Jiangnan’s late‑season rice and the middle and lower Yangtze River’s 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 even soared to 50,000 per mu. Field damage has resulted in a dead‑sheath rate of 1% to 3%, with peak rates as high as 16% to 30%; the dead‑heart rate stands at 0.7% to 1.2%, with local peaks 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 and the middle‑season rice areas of the Jiangnan region, as well as in the single‑cropping rice areas of Southwest China, the incidence of diseased plants generally ranges from 3% to 11%, with higher rates of 15% to 20%; the incidence of diseased tillers typically falls between 8% and 15%, reaching 30% to 40% in some cases. In South China and the Jiangnan region’s late‑season rice areas, as well as in the single‑cropping rice zones of the middle and lower reaches of the Yangtze River, sheath blight has entered a phase of lateral spread, with the incidence of diseased plants generally ranging from 1% to 5%, and higher rates from 5% to 10%; the incidence of diseased tillers usually stands at 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 South China and the middle rice‑growing regions of Jiangnan, as well as in the single‑crop rice areas of Southwest China 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 locally 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 in these areas, particularly blast disease of the panicle neck, as well as the reproduction and proliferation of “two‑migration” pests in the Southwest rice region. 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