Analysis of the Occurrence Trends of Major Pests and Diseases in the Mid-to-Late Stages of Corn Growth

Release Date:

2020-08-06

Recently, the Ministry of Agriculture and Rural Affairs Corn The expert panel, based on the current… Corn Based on an integrated analysis of pest and disease baseline populations, regional distribution, and cropping practices, together with projected weather conditions, it is anticipated that this year… Corn In the mid-to-late growth stages, pest and disease incidence was generally moderate to severe, slightly higher than the long-term average but comparable to last year. Migratory pests such as the fall armyworm, third-generation armyworms, second-generation grass webworms, and cotton bollworms have affected… Corn The production threat is significant, Corn Sesamia, large spot disease, and brown spot disease are widespread; peak period of damage: northern regions. Corn In most growing regions, the planting period falls from late July to late August, in southern areas. Corn The planting season is sustainable until the end of October.
Trend in the second half of the year
It is expected that in the second half of the year, nationwide… Corn Pests and diseases occurred on 820 million mu of farmland, with pest infestations affecting 560 million mu and disease outbreaks covering 260 million mu—down 4%, 3%, and 7% year on year, respectively. Migratory pests have… Corn The mid- to late-stage production faces significant threats. Among these, the fall armyworm poses a major threat to the Southwest, South China, and the Jiangnan region during the summer and autumn seasons. Corn Severe outbreaks have occurred in border regions such as Yunnan and Guangxi; the areas affected in the Huanghuaihai Plain and Northwest China are expected to continue expanding, with overall occurrences remaining localized or sporadic, covering approximately 10 million mu.
Overall, the three generations of armyworms are expected to occur at moderate levels, with localized areas in Northeast China, North China, the Huang-Huai region, and Southwest China experiencing high-density outbreaks. The affected area is estimated at 30 million mu.
The second generation of the grass cutworm is likely to occur at a severe level in Inner Mongolia and surrounding areas, with an affected area of 6 million mu.
The third and fourth generations of the cotton bollworm may reach a moderately severe level in the Huang-Huai-Hai region, while other regions will experience moderate infestations, with an affected area of 60 million mu.
Corn The stem borer is moderately prevalent across most of Northeast China, North China, the Huanghuai region, and Northwest China, with a cumulative infested area of 220 million mu‑times across all generations.
Aphids are moderately prevalent across most of Northeast, North, and Northwest China, affecting an area of 60 million mu.
Spider mites and the two-spotted leaf beetle are moderately prevalent in parts of Northwest and North China, with infestations covering 25 million mu each.
The migratory locust causes some damage in certain arid regions of northern China, with an infestation covering 10 million mu.
Large spot disease is severely prevalent in the western part of Northeast China, while moderate outbreaks are observed across most of Northeast China, northern North China, eastern Northwest China, and localized areas in Southwest China, affecting 63 million mu. Small spot disease occurs at a moderate level in southern Huanghuai and localized areas of Southwest China, covering 42 million mu. Brown spot disease is moderately prevalent in the Huanghuai–Hai region, with an affected area of 33 million mu.
In addition, diseases such as Curvularia leaf spot, sheath blight, and southern rust will also cause some damage.
Basis of the Forecast
(1) High baseline pest population
The fall armyworm is currently present in 1,082 counties across 22 provinces nationwide, with its northern range now extending to the north bank of the Yellow River—approximately 1.5 degrees of latitude farther north than at the same time last year. In Shandong, larvae were observed a week earlier, while in Ningxia, adult moths appeared 20 days earlier than last year. Nationwide, control measures have been implemented on a cumulative area of 13.6 million mu, 1.24 times the extent of the infested area. Corn The incidence of damaged plants has generally been kept below 5%. Recently (July 10–16), some areas have experienced peaks in moth populations: at monitoring lamps, cumulative trap catches reached 50–200 moths in Kaiping, Deqing, Huidong, and Heshan in Guangdong, as well as in Napo, Guangxi; at high-altitude monitoring lamps, cumulative catches ranged from 50 to 100 moths in Nan County, Hunan; Heshan, Guangdong; and Mengla, Yunnan, while in Daye, Hubei; Yongshun, Hunan; Raoping, Guangdong; Hepu, Guangxi; Longling and Jiangcheng, Yunnan, they reached 120–530 moths. At sex pheromone traps, cumulative catches were 30–65 moths in Baiyun and Huadu, Guangdong, and Daye, Hubei, whereas in Luquan, Xundian, Longyang, Fengqing, Gengma, Mile, Hekou, Guangdong’s Zengcheng, and other locations, they ranged from 100 to 1,000 moths.
The second generation of armyworms has infested 24 million mu in the Southwest, the Huang–Huai–Hai region, and Northeast China. In most areas, post‑control average pest densities are below one larva per square meter; however, localized averages remain higher in the Southwest and Northeast, with Yunnan and Liaoning reporting 1.5–1.8 larvae per square meter. Recently, some high‑altitude light‑trap monitoring stations in the Northeast have recorded unusually high moth catches: Changling, Jilin, reported 76 moths from July 1 to 20, up from 55 during the same period last year; Shuangcheng, Heilongjiang, recorded 409 moths from July 1 to 20—3.5 times and 5.8 times the levels observed in the same periods of the previous two years, respectively.
In the main outbreak area, the overwintering generation of the grass webworm has infested 16.21 million mu of land in Inner Mongolia, with moth populations in fields declining markedly since mid-July. First-generation larvae have been reported on 7.90 million mu, including 3.37 million mu in agricultural fields. The most severe outbreaks are concentrated in Baotou and Bayannur in the western region, where average larval densities in farmland range from 23 to 30 larvae per square meter; as of July 15, Dalad Banner… Corn Soybean In the intercropped fields, the density of field cutworm pupal cocoons was 40 per square meter; in the alfalfa fields, it was 1 per square meter; no pupal cocoons were detected elsewhere.
Corn The population of stem borers has been declining year by year, and in Northeast China during the spring season… Corn In the main production areas, the number of live pests per 100 tillers after winter has dropped below 50, more than 60% lower than the long-term average, and the first generation… Corn The average number of stem borers per 100 plants was below 10 in most areas.
(2) Corn The growth period and cultivation practices are conducive to the occurrence of pests and diseases.
North Corn Continuous monoculture leads to vigorous, tall growth and dense canopy closure in the field, creating favorable conditions for the occurrence and damage caused by diseases and pests. In particular, fields with lax management and abundant weeds provide ideal conditions for the concentrated oviposition and subsequent damage by the oriental armyworm and the rice stem borer. Southern regions. Corn Intercropping, summer–autumn season Corn The growing period varies; at present, in regions such as the Huang-Huai-Hai Plain and Northwest China… Corn Most are in the trumpet‑mouth stage, making them highly susceptible to feeding damage by the fall armyworm. Meanwhile, in China… Corn There are few disease- and pest-resistant varieties planted, such as Xianyu 335, etc. Corn The proportion of susceptible varieties planted is high; in various regions… Corn Diseases such as large spot and brown spot have been recurring year after year, and the high rate of straw return to the field further favors their occurrence.
(3) Meteorological conditions across most regions Corn Favorable conditions for the occurrence of diseases and pests
According to forecasts from the National Climate Center, eastern Inner Mongolia, western Northeast China, most of the Huanghuai region, northern Jianghuai, and the northwestern part of Southwest China are expected to experience 20%–50% above-normal rainfall in August, which will be conducive to the proliferation of the oriental armyworm, the grass webworm, and… Corn Disease incidence: In August, temperatures in southern Jianghuai, Jiangnan, South China, and the southern parts of Southwest China were 1–2°C above normal, with precipitation at or below average, which is unfavorable for the occurrence of fall armyworm and oriental armyworm, but favorable for damage caused by cotton bollworm and aphids. In the second half of the year, the number of typhoons making landfall in China is slightly higher than usual for this period, which will facilitate the spread and epidemic development of southern rust in the Huang-Huai-Hai region.