Major outbreak of southern corn rust? Early signs are already appearing in many regions—urgent warning!

At present, major corn-producing regions are in a critical period for yield formation; however, the warm, moist airflow on the periphery of Typhoon Goni is creating favorable conditions for the interregional spread of southern corn rust. The muggy, “sauna‑like” weather is further increasing the risk of a severe outbreak of this disease.

Southern corn rust is caused by Puccinia polysora. Puccinia polysora Underw. It is a highly destructive airborne fungal disease that primarily occurs in tropical and subtropical maize-growing regions. In recent years, driven by climate change, the disease has begun to spread into higher-latitude areas and has gradually become a major pathogen in China’s Huang–Huai–Hai summer maize region.

Southern corn rust is a globally distributed, air-borne disease that was first reported in South Africa in 1949, causing yield losses of over 50% in maize. In China, it was first detected in the 1970s in Hainan Province, particularly in Ledong, Lingshui, and Yacheng. In 1997, an outbreak occurred in Chun’an County, Zhejiang, with infected maize accounting for 22.1% of the autumn maize acreage. Following 1998, the disease spread rapidly across summer maize‑producing regions in the Yellow–Huai–Hai Plain, including Hebei, Henan, Shandong, and Shanxi. In 2004, it once again became widespread in China’s major maize‑growing areas: in Henan, the affected area reached 27.8%, with severe outbreaks showing average incidence rates of 60%–90%; in Laizhou, Shandong, the average incidence ranged from 30% to 60%; and in Luanping County, Hebei, the affected area totaled 5,333 hectares. ² In 2011, Luohe City experienced a severe outbreak of southern rust, with infected plant rates exceeding 50% in heavily affected areas. In 2014, the disease broke out in autumn maize-growing regions of Wuhan, Hubei, resulting in yield reductions of 60% to 70%, and in some severely affected fields, total crop failure. By 2015, the nationwide area affected by southern rust had reached 5.36 million hectares. ² Moreover, the incidence in the major summer maize‑growing regions of the Huanghuaihai Plain was significantly more severe than usual. Henan Province recorded the largest affected area and the most serious damage; during the peak period, the proportion of infected plants ranged from 18.5% to 66.6%, with an average disease‑leaf rate of 30.7%, and in severely reinfested fields both the plant‑infection rate and the leaf‑infection rate reached 100%. In 2021, under the influence of Typhoon “Yinhua,” the Huanghuaihai region experienced widespread and severe outbreaks, characterized by extensive acreage, rapid spread, and high disease intensity. The percentage of infected fields was 100%, with disease‑leaf and plant infection rates both exceeding 70%; in the most severely affected areas, these rates approached 100%, resulting in yield reductions of 20%–30%. Once southern rust breaks out extensively in summer maize‑producing areas, the leaves are quickly covered within about a week by orange‑yellow urediniospore masses, leading to rapid drying and death of the foliage and causing yield losses of varying degrees.

Phenotype of Southern Corn Rust

Major outbreak of corn rust? Early signs are already appearing in many regions—urgent warning!

01

National Agricultural Technology Center: The projected affected area for southern rust is 80 million mu, with the peak incidence occurring from mid-August to late September.

The latest pest and disease report issued by the National Agricultural Technology Extension Service Center indicates that, influenced by the recent northward movement of Typhoon No. 3 “Gami,” the inoculum of southern corn rust may spread to the Huanghuaihai region. Moreover, the heavy rainfall and significant temperature drop brought by the typhoon will create warm, humid weather conditions, which are highly conducive to spore deposition, infection, and the outbreak and widespread dissemination of southern corn rust.

Based on expert consultations and a comprehensive analysis of factors including pathogen inoculum, cultivar susceptibility, the northward movement of typhoons, weather conditions, and cropping systems, southern corn rust is expected to occur at moderate to severe levels in the major corn‑producing regions of the Huanghuaihai Plain this year, posing a significant threat to corn production. The nationwide affected area is projected to reach 80 million mu, with the peak epidemic period occurring from mid‑August to late September. According to model forecasts, over the next two to three weeks, most of Henan Province, localized areas in Jiangxi, Hunan, and Hubei, northern Zhejiang, Anhui, and Jiangsu, western Shandong, as well as Hebei, Beijing, and Tianjin, will face a high risk of outbreaks and widespread epidemics of southern corn rust.

02

Henan: Issues a high-risk warning for southern corn rust; experts urge the adoption of preventive measures, and the Department of Agriculture has released management guidelines.

On July 24, the Henan Provincial Meteorological Bureau and the Department of Agriculture and Rural Affairs jointly issued a high‑risk weather warning for southern corn rust, noting that maize in Henan is currently at a critical stage of yield formation. Typhoon “Goni” is expected to move northward from the 25th to the 28th, and its peripheral warm, moist air flow will create favorable conditions for the interregional spread of southern corn rust. Most areas within the province are classified as high‑risk zones, making scientifically sound preventive measures to safeguard maize production an urgent priority.

“Following a typhoon, outbreaks of southern corn rust may occur, primarily causing leaf drying, reduced photosynthetic efficiency, and impaired grain filling, ultimately leading to yield losses,” said Qiao Jiangfang, Director of the Corn Tillage and Cultivation Research Laboratory at the Institute of Cereal Crops, Henan Academy of Agricultural Sciences, and Head of the Provincial Autumn Grain Expert Guidance Group.

Agricultural meteorology experts are urging all regions to take proactive preventive measures, prioritizing prevention and seizing opportunities during breaks in rainfall to implement control efforts. In fields where disease has already appeared, apply fungicides and insecticides 1–2 times, using formulations tailored to the specific disease severity. With corn, soybeans, and other autumn crops currently in a critical phase of rapid growth, following several rounds of heavy rainfall in Henan, the Department of Agriculture and Rural Affairs has issued technical guidelines for post‑disaster field management. For areas with waterlogged soils, carry out timely inter‑row cultivation and soil hilling; in excessively wet fields, consider aerial application of appropriate solutions or growth regulators via drone. For corn, strengthen pest and disease forecasting and, when necessary, spray suitable fungicides and insecticides.

03

Hebei: Defense measures issued as the meteorological risk of widespread damage from southern corn rust is high!

On July 26, the Hebei Provincial Meteorological Bureau and the Hebei Provincial Department of Agriculture and Rural Affairs jointly issued a meteorological risk warning for southern corn rust: From July 27 to 29, the remnants of Typhoon “Gami” are expected to affect Hebei Province. The warm, moist air on its periphery will carry spores of southern corn rust across regions, while favorable temperature and humidity conditions will greatly facilitate long-distance dispersal, deposition, infection, and widespread damage. According to reports from the National Agricultural Technology Extension Center, southern corn rust has already become widespread in southern corn‑producing areas such as Fujian. In recent days, disease lesions have been detected in Nanyang, Zhoukou, Xuchang, and other locations in Henan, with an ample supply of pathogen inoculum. Consequently, most parts of Hebei Province face a high meteorological risk of widespread outbreaks and severe damage from southern corn rust.

04

Yantai, Shandong: Be on alert for the outbreak of southern corn rust.

Southern corn rust is a major epidemic disease that severely threatens maize production. In the early stages of infection, circular, scattered, irregular yellow spots about 1 mm in diameter appear on the leaves. After 1–2 days, these spots develop into blister-like raised structures; over the next 3–5 days, the host epidermis beneath the blisters ruptures, releasing golden‑yellow or orange powdery summer spores. Even mild infections can impair photosynthesis, increase water loss, and reduce 100‑kernel weight. In severe cases, leaves wither prematurely and may spread throughout the plant. Later in the season, heavily affected leaves often wilt due to nutrient depletion, or the stalks lodge. In severely infected fields, yield losses can exceed 20%. In recent years, southern corn rust has become the principal disease in the Huang‑Huai‑Hai summer maize‑growing region, with more frequent large‑scale epidemics and an earlier onset compared with typical years.

Since July, Yantai City has experienced significantly above‑average rainfall, creating field conditions—warmth and humidity—that are highly conducive to the infection and spread of southern rust. According to the National Meteorological Center, Typhoon No. 3 “Gami” is expected to make landfall in Fujian on the afternoon or evening of the 25th and gradually move northward, with a strong likelihood of bringing substantial quantities of southern rust pathogen to the Huanghuaihai corn‑growing region. Meteorological forecasts further indicate that from late July through August, the city’s rainfall will be above normal. Taking into account factors such as the path of pathogen dispersal, anticipated weather conditions, host cultivar resistance, and management practices, the risk of a widespread outbreak of southern rust in this year’s summer corn crop is projected to be high. The total affected area is estimated at 320,000 mu, with the peak epidemic period occurring from mid‑August to mid‑September. At present, southern rust has already been detected in Xuchang, Zhoukou, Nanyang, Kaifeng, and other areas in Henan Province, with an earlier onset and a greater number of disease foci than during the same period last year. A large reservoir of pathogen can be transported northward by the typhoon. The summer spores of southern rust are well adapted to germinate and penetrate hosts under high‑temperature conditions, then proliferate within plant tissues; however, visible symptoms typically require cooler temperatures. The extensive rainfall brought by the typhoon, coupled with temporarily lower-than‑normal temperatures, could easily trigger widespread, concentrated symptom expression across regions and lead to rapid escalation of damage.

In light of the above, all districts and cities must attach great importance to this issue, strengthen monitoring, conduct thorough field surveys, and promptly issue early warnings and forecasts, ensuring early detection, early warning, and early response. They should promptly develop contingency plans for prevention and control, stockpile adequate emergency supplies, and, in conjunction with key measures such as the “one‑prevent‑two‑reduce” approach for corn, vigorously implement unified pest management, joint prevention and control, and community‑based prevention and treatment, thereby making every effort to contain outbreaks and safeguard the security of autumn grain production.

Source: Hebei Provincial Plant Protection Association