Early-spring incidence dynamics of major wheat diseases and pests, along with trends for the next phase, call for enhanced monitoring and surveying.

Currently, most wheat-growing areas in Southwest China are at the booting to heading stage, while Yunnan is in the grain-filling stage; in the southern regions where early sowing occurred, crops have entered maturity and are being harvested. In the middle and lower reaches of the Yangtze River, wheat is progressing from jointing to booting. In much of the Huanghuai and North China plains, wheat has already greened up, with Henan entering the tillering–jointing phase. In Northwest China, green-up is underway, and Shaanxi has reached the jointing stage. Spring-sown wheat areas have largely completed planting. As temperatures gradually rise, major diseases and pests in key wheat-producing regions are beginning to intensify. Specifically, stripe rust is entering a localized spreading phase in the Southwest and the Han River basin, while sheath blight and stem base rot are reaching their peak incidence in the Huanghuai and North China wheat belts. Wheat aphids, spider mites, and powdery mildew are at their initial outbreak stages across major wheat-growing areas. As of March 15, the total area affected by major wheat diseases and pests stood at 101.55 million mu, with overall infestation levels remaining relatively light—making this the fourth‑lightest occurrence for the same period since 2010.

I. Dynamics of Major Pest and Disease Outbreaks

Stripe rust The spread in the Han River basin has accelerated. As of March 15, disease was observed in 192 counties (cities, districts) across seven provinces and municipalities—Yunnan, Sichuan, Guizhou, Chongqing, Shaanxi, Hubei, and Gansu—covering an area of 754,200 mu. This represents a 92.7% reduction compared with the same period in 2020, the lowest level since 2013; the number of affected counties decreased by 33.6% year-on-year, though it was 1.6% higher than during the same period in 2022, when the outbreak was mild. Overall, the disease situation in the Southwest wheat-growing region is comparable to that of 2022 but milder than the long-term average. In Yunnan, Sichuan, Guizhou, and Chongqing, 171 counties (cities, districts) reported 602,900 mu of affected land, with both the number of affected counties and the affected area down 1.8% and 54.5%, respectively, relative to the average for the same period from 2018 to 2022. Specifically, in nine cities (prefectures)—including central and eastern Yunnan, Zhong County and Kaizhou in Chongqing—some fields are in a phase of widespread dissemination. Meanwhile, in the rest of Yunnan’s major wheat‑growing areas, eastern and southern Sichuan, northwestern Guizhou, Tongnan and Wushan in Chongqing—totaling 20 cities (prefectures) and 49 counties (cities, districts)—disease is occurring sporadically in localized patches, while other localities report only isolated cases. In the Han River basin, disease severity remains lower than at the same time in 2022, yet its recent expansion has been rapid. In Hubei and Shaanxi, 19 counties (cities, districts) across five cities reported 141,900 mu of affected land, with the number of affected counties and the affected area down 33.3% and 45.3%, respectively, year on year, and 64.3% and 93.7% below the average for the same period from 2018 to 2022. Over the past two weeks, eight cities and 15 counties in eastern Hubei, the Jianghan Plain, and the Han River region have seen new disease outbreaks, with symptoms beginning to appear more concentratedly. Jingling County in Jingzhou, Hubei, has entered a phase of widespread dissemination, while in the central Jianghan Plain—Jingzhou, Jingmen, Qianjiang—and along the Han River in Shaanxi—four cities and ten counties—are experiencing patchy outbreaks. Isolated cases continue to occur in eastern Hubei and the northern and western parts of the Jianghan Plain.

Sheath blight In the major wheat-producing regions of central and eastern China, the disease affected 38.05 million mu, the lowest level for this period since 2010 and 31.6% lower than the 2010–2022 average. The Huanghuai and southern North China wheat areas experienced relatively severe outbreaks, with average incidence rates ranging from 5.8% to 7.4% in western Shandong, central and eastern as well as northern Henan, and northern Anhui. In southern Hebei, northern Anhui, and localized fields in Shandong, incidence rates reached 56% to 76%, while in parts of northern Jiangsu, local incidence soared to 95%. Elsewhere, most other wheat-growing areas reported only mild infections.

Stem base rot disease In the North China wheat-growing regions of Shandong, Henan, Hebei, and Shanxi, the disease has affected 8.03 million mu, a decrease of 26.5% compared with the same period in 2022. Specifically, it is widespread across the southern, central, eastern, and northern wheat‑growing areas of Shandong, with average incidence rates ranging from 4.1% to 7.9%. In Henan, the provincial average disease‑affected field rate is 9.2%, and the average incidence rate is 1.9%, with the highest recorded at 29%; both figures exceed last year’s levels. The eastern and northern wheat‑growing areas of Henan have experienced relatively severe outbreaks, with average incidence rates between 3.6% and 7.9%. In Hebei, the average incidence rate is 0.9%, with localized peak rates as high as 20% in the southern wheat‑growing region.

Powdery mildew In the central and western wheat-growing regions, the affected area totaled 2.42 million mu, the fifth smallest for the same period since 2010, down 24.1% from the 2010–2022 average. In the southwestern wheat areas—including Sichuan, Chongqing, Yunnan, and Guizhou—the average disease‑leaf rate ranged from 1.8% to 12.0%, with a locally highest rate of 100% in Wenshan, Yunnan. In the Han River basin—covering Shaanxi, Hubei, and Henan—the average disease‑leaf rate was between 0.1% and 0.6%, with a peak of 24% in Yichang, Hubei. In Shanxi, the average disease‑leaf rate was 2.7%, with Ruicheng recording a maximum average of 40%.

Wheat aphid It has occurred widely across most wheat-growing regions, affecting 15.75 million mu‑times—marking the sixth‑smallest area for this period since 2010 and a 15.3% reduction compared with the 2010–2022 average. In the Southwest wheat region, the pest has entered its peak phase, with average aphid counts per 100 plants ranging from 108 to 235 in Chongqing, Guizhou, and Sichuan, and reaching 433 in Yunnan; in Dehong, Yunnan, the highest count recorded was 11,000 aphids per 100 plants. In the Jianghuai and Huanghuai wheat regions, Hubei reported an average of 94 aphids per 100 plants, with Jingshan recording a peak of 8,250; Anhui, Jiangsu, and Shaanxi averaged 13–25 aphids per 100 plants; while Hebei, Shandong, Shanxi, and Henan averaged 2–9 aphids per 100 plants, with Chuzhou, Anhui, reporting a peak of 3,000 aphids per 100 plants.

Spider mite In the major wheat-producing regions of eastern China, pest outbreaks occurred on 36.4 million mu, marking the fifth-largest figure for the same period since 2010 and a 15.7% increase compared with the 2010–2022 average. The average number of pests per linear foot was 47 in Hubei and 13–42 in Hebei, Shanxi, Shandong, and Henan. In certain wheat-growing areas of the Jianghuai and northern Huai regions, pest densities were relatively high, with the highest recorded count reaching 3,400 pests per linear foot in Yicheng, Hubei.

II. Development Trends in the Next Phase

According to forecasts from the National Meteorological Center, during March, temperatures across most of China’s wheat-growing regions are expected to be near or above normal for this time of year, with northern and central North China experiencing temperatures 1–2°C higher than average. Areas including central and southeastern Hubei, central and southern Anhui, and central and southern Jiangsu, as well as southeastern Henan, are likely to receive more than 50 mm of precipitation. Over the next two weeks, temperatures in most wheat-growing areas are projected to exceed normal levels by 1–3°C, while the southeastern parts of the Northwest wheat region, the eastern parts of the Southwest wheat region, and much of the Jianghan and Jianghuai plains are expected to see one to three episodes of significant rainfall. Overall, these meteorological conditions are favorable for wheat growth and development, and highly conducive to the proliferation of pests and the spread of diseases.

In the next phase, wheat stripe rust is expected to manifest prominently in the eastern and northern parts of the Southwest wheat region and in the Han River basin, while disease incidence will gradually appear across the middle Yangtze, Jianghuai, and southern Huanghuai wheat areas. In the Southwest, effective disease management and strict control of initial inoculum levels are essential. In “bridge” regions such as Hubei, Anhui, and Henan, enhanced monitoring and surveys, coupled with rigorous localized interventions to protect broader areas, will help slow the eastward and northward spread of the pathogen and alleviate pressure on the major wheat-producing areas of central and eastern China. With little significant rainfall forecast for most of the Huanghuai and North China wheat regions in the near term, populations of wheat aphids and spider mites are likely to increase rapidly, while sheath blight and stem base rot will enter their peak period of lateral spread. Close attention to disease dynamics and timely implementation of threshold‑based control measures are critical to keep pest densities low and contain disease progression before tillering, thereby ensuring healthy wheat growth and securing yield potential.

Source: Agricultural Inputs Herald