From late July to late August is the peak period for corn diseases and pests; farmers must strengthen prevention and control measures.

　　From July 16 to 18, the National Agricultural Technology Center convened the 2018 National… in Harbin, Heilongjiang Province. Corn and Cotton Seminar on the Consultation and Forecasting of Pest and Disease Trends. Participants from 23… Corn The pest monitoring and forecasting technicians and relevant experts from the producing provinces (autonomous regions, municipalities) are summarizing… Corn Based on the early-stage incidence of pests and diseases, and in light of the current situation… Corn Baseline incidence of pests and diseases, Corn Based on a comprehensive analysis that integrates tillage and cultivation practices, crop‑rotation patterns, and projections of future climate trends, it is anticipated that this year… Corn In the mid-to-late growth stages, pest and disease incidence was generally moderate, with the third-generation armyworm and ear-stage damage. Corn Sesamia inferens, cotton bollworm, southern corn leaf blight, and brown spot disease are locally severe; the peak period of damage from these pests and diseases occurs from late July to late August.

1. Corn Overview of Early-Season Pest and Disease Incidence

     Corn Early-stage pests and diseases are primarily those of the first generation. Corn The main pests include stem borers, the second generation of armyworms, the first generation of grass cutworms, the second generation of cotton bollworms, the two-spotted armyworm, underground pests, thrips, and sheath blight. Overall, the incidence is relatively mild, at a level similar to that of recent years, with an affected area of 318 million mu‑times; among these, Corn Pest outbreaks occurred on 289 million mu of farmland, Corn Disease incidence totaled 28.5 million mu‑times. First generation. Corn The stem borer is occurring at moderate to severe levels in the northern part of Northeast China, while in other areas of the Northeast, North China, the Huanghuai region, and most of Southwest China, it is expected to occur at mild to moderate levels. At present, with the exception of the first generation in the Northeast, which is currently in its damage‑causing phase, the second generation in other regions… Corn The stem borer has begun to cause damage. The second generation of the armyworm is generally at a moderate level of occurrence, with high-density fields reported in parts of Heilongjiang, Liaoning, Inner Mongolia, Shaanxi, and Shanxi, where the peak density reached 1,500 larvae per 100 plants. The first generation of the grass cutworm is locally severe in Xing’an League and Hulunbuir in Inner Mongolia, as well as in Baicheng, Jilin. Corn High-density larvae were detected in amaranth, with peak densities reaching 15,000 per 100 plants and 1,000 per square meter, respectively. The two-spotted armyworm occurred at moderate levels in localized areas of Shandong, Shanxi, and Hebei, while in other parts of the Huanghuaihai region it was relatively mild. The second generation of the cotton bollworm was observed at a mild level across North China, the Huanghuai region, and Northwest China, less severe than the previous year. Soil-dwelling pests ranged from moderate to moderately severe in parts of Northeast China, North China, and Northwest China. Thrips occurred at a relatively severe level in localized areas of North China and Northwest China. The two-spotted leaf beetle was moderately severe in certain areas of Inner Mongolia and Shanxi. Pests such as the beet armyworm, snails, and the brown‑footed leaf beetle caused significantly increased damage in the Huanghuaihai region. Sheath blight was moderately prevalent across most of Southwest China. Corn In the Northeast, North China, and Northwest regions, large spot disease is progressing into its period of economic impact, while in the Huang-Huai-Hai region, brown spot disease is gradually entering its damaging phase (see Table 1 for the affected areas of each disease and pest).

2, Corn Trends in the Occurrence of Pests and Diseases in the Mid-to-Late Stages

(1) Types and Area of Occurrence

     Corn In the mid- to late growth stages, the major pests and diseases are borers, leaf-eating insects, sap-sucking pests, and foliar diseases. Corn Sesame stem borers, cotton bollworms, aphids, southern corn leaf blight, northern corn leaf blight, and brown spot are widespread and cause significant damage; spider mites, two-spotted lady beetles, Curvularia leaf spot, smut, common smut, sheath blight, stem rot, ear rot, and gray leaf spot also inflict some harm in certain regions. It is projected that nationwide… Corn In the mid-to-late stages, pest and disease outbreaks affected 844 million mu‑times, with pests accounting for 571 million mu‑times and diseases for 274 million mu‑times (see Table 1 for the projected affected areas and key regions of each pest and disease).

(2) Severity and Key Areas

Borer pests. Corn The first generation of the cotton bollworm is moderately severe in Heilongjiang and the northeastern part of Inner Mongolia; the second generation is severely prevalent in southwestern Heilongjiang, with moderate to severe incidence in eastern Inner Mongolia, western Jilin, southeastern Liaoning, Sichuan, and Xinjiang, and moderate occurrence elsewhere. The third generation is moderately severe in Hebei, Shanxi, Henan, and Hubei, with mild to moderate incidence in other regions. During the heading stage, the cotton bollworm is moderately prevalent in the Huanghuaihai, Northwest, and southern Northeast regions, while the peach fruit borer is causing increased damage in the Huanghuaihai area.

Leaf‑feeding pests. The three generations of the armyworm are generally at moderate levels, with localized areas in Northeast, North China, Northwest China, and the Huanghuai region experiencing high‑density, concentrated damage. The second generation of the grass webworm may occur at a relatively severe level in eastern Inner Mongolia and adjacent areas. The two‑spotted leaf beetle is expected to be moderately to severely prevalent in Shanxi, Inner Mongolia, and Heilongjiang, while most other regions will see mild to moderate infestations.

Sucking pests. Aphids are moderately prevalent across Northeast, North China, Northwest, and most of the Huanghuai region; spider mites are slightly to moderately prevalent in the Northwest and most of North China.

Diseases. Large spot disease is severe in eastern Northeast China, while it occurs at moderate levels in central and western Northeast China, northern North China, eastern Northwest China, and localized areas of Southwest China; small spot disease is moderate in southern Huanghuai and localized areas of Southwest China; brown spot disease is moderate in the Huanghuai–Bohai region and eastern Inner Mongolia; Cercospora leaf spot is moderate in the Huanghuai region and southern Northeast China; gray leaf spot is moderate in the mountainous areas of Southwest China and most of Northeast China; sheath blight is moderate to severe in most of Southwest China and localized areas of Northeast China; southern rust may be severe in southern Huanghuai and other regions; stem rot poses a high risk of severe occurrence in the Huanghuai–Bohai region. In addition, diseases such as smut and ear rot will also cause some damage in localized areas.

3. Forecast Basis

(1) The initial population levels of the grass cutworm and plant diseases are relatively high, Corn The initial population levels of stem borers, armyworms, and cotton bollworms are relatively low.

The weighted average residual pest density of the second-generation armyworm across different types of fields ranged from 1.2 to 6 larvae per square meter in Heilongjiang, Liaoning, Inner Mongolia, Sichuan, Yunnan, and Guizhou, while in other provinces it remained below 1 larva per square meter. Recent monitoring of adult armyworm populations nationwide shows that in Zhaozhou, Heilongjiang, from July 7 to 17, the light trap recorded a cumulative total of 37 moths, and the moth‑attracting device captured 124 moths; in Gongzhuling, Jilin, the peak daily catch reached 36 moths; in Zhangwu, Liaoning, a moth‑peak occurred from the 9th to the 13th, with seven monitoring sites collectively recording 998 moths on peak days, and a single trap capturing as many as 142 moths. During the first half of July, high‑altitude light traps reported the following: in Shuangcheng, Heilongjiang, a cumulative total of 31 moths was recorded, with 8 moths on the peak day; in Horqin District, Inner Mongolia, the peak day saw 71 moths; in Laizhou, Shandong, 41 moths were accumulated; in Fengtai, Anhui, 8 moths were recorded; and in Zhuanglang, Gansu, 77 moths were accumulated, with 15 moths on the peak day. In all these locations, moth catches were lower than the same period last year. Meanwhile, Changling, Jilin, recorded a cumulative total of 1,398 moths, with 750 moths caught on July 13—the peak day arrived one week earlier than usual—and the total catch was seven times that of the previous year. In Zhangwu, Liaoning, 285 moths were accumulated, three times last year’s level; in Luan County, Hebei, 1,642 moths were recorded, forty times last year’s figure, with 805 moths on the peak day.

The overwintering generation of the grass webworm and its first-generation larvae have spread over a wide area and are causing severe damage. The density of first‑generation larvae in crop residues is 1.27 per square meter in Inner Mongolia, 0.01 per square meter in Jilin, and 0.06 per square meter in Ningxia. Recently, localized areas in Inner Mongolia have experienced peak moth‑catching events for the first generation: at the Ulanhot high‑altitude monitoring lamp, 20,000, 47,000, and 32,000 moths were trapped on July 9–11, with 7,520 moths on the 13th; the monitoring lamps recorded 592, 1,984, and 848 moths from July 9 to 11, and 1,290 on the 13th. In Tuquan County, the high‑altitude monitoring lamp captured more than 10,000 moths on July 11 and 2,950 on the 13th, while within a hundred steps of the lamp, 1,500–2,000 moths were flushed out; by contrast, only a few moths were disturbed within a hundred steps of the fields’ surrounding weeds and grasslands. In Arong Banner, Hulunbuir, the high‑altitude monitoring lamp caught 12,000 moths on July 11, and in Hailar and Mo Banner, in barren lands and areas densely populated with amaranth, 300–600 moths were flushed out within a hundred steps. In Nenjiang, Heilongjiang, the monitoring lamp accumulated 136 moths from the 13th to the 16th, with 5 moths detected within a hundred steps.

The second-generation cotton bollworm is generally expected to occur at a relatively low level across North China, Northwest China, and most of the Huang-Huai region, with a low initial population density. Corn 、 Peanut 、 Soybean In fields of vegetables, Chinese medicinal herbs, oilseed sunflower, and other crops, the pest incidence was observed as follows: in Tianjin, the maximum number of pests per 100 plants reached 10; in Henan, the average was 2 per 100 plants; in Hebei, it generally ranged from 1 to 5 per 100 plants, with heavily infested plots showing 8 to 20 per 100 plants. The residual pest population remained lower than last year.

Statistics of one generation across various regions Corn The average number of stem borers per 100 plants was 47 in Heilongjiang, with 64 live borers per 100 plants after winter in the first-generation region; 40 in Guizhou; 31 in Chongqing; and 10–27 in Hunan, Jiangsu, Shandong, Jilin, Liaoning, and Inner Mongolia. In all other provinces, the count remained below 10, with most regions showing relatively low initial infestation levels.

Various places Corn Diseases such as large spot and brown spot have been recurring year after year, and the increasing proportion of straw returned to the field has resulted in a substantial reservoir of pathogenic fungi. At present, Corn Diseases such as leaf spot, sheath blight, small spot, and rust have begun to occur across various regions and are showing a trend of gradual intensification. Among them, Corn In Inner Mongolia, the incidence of large spot disease ranges from 5% to 20%; in Shanxi, the average incidence is 1% to 2%, with a maximum of 5%; in Hebei, the mean incidence is 8.5%, with a peak of 21%; in Jilin, the incidence is 1.1%; and in Pengyang and Yuanzhou, Ningxia, the incidences are 4.8% and 15%, respectively, with corresponding leaf‑disease rates of 1.6% and 1.8%.

(2) Corn The crop varieties and cropping systems are conducive to the occurrence of multiple pests and diseases.

Our country Corn There are few disease- and pest-resistant varieties planted, such as Xianyu 335, etc. Corn The proportion of susceptible varieties planted is high. Northern regions. Corn The practice of contiguous planting facilitates the widespread occurrence and damage caused by pests and diseases, while some poorly managed fields create favorable conditions for the concentrated outbreak of armyworms and grass cutworms. Meanwhile, Corn In the later growth stages, the plants become tall and the canopy becomes dense in the field. Corn The difficulty of pest and disease control has led to a worsening of damage caused by pests and diseases.

(3) Future meteorological conditions across most regions Corn Favorable conditions for the occurrence of diseases and pests

According to forecasts from the National Climate Center, during the second half of July through the first half of August, eastern Northwest China, North China, southern Northeast China, and northern Huanghuai regions are expected to experience 20%–50% above-normal precipitation. Temperatures across most of northern China are likely to be near normal, which will facilitate the interregional movement and population reproduction of migratory pests such as the oriental armyworm, the grass webworm, and the cotton bollworm, while also being conducive to… Corn Moisture‑loving pests and diseases such as stem borers, large spot disease, small spot disease, brown spot disease, and Curvularia leaf spot are expected to occur. In southern Huanghuai and northern Jiangnan, rainfall is 20%–50% below normal, which will favor the outbreak of drought‑tolerant pests like cotton bollworms and aphids in these regions. It is forecast that 3–4 typhoons will make landfall in China, exceeding the long-term average for this period (about 2), and the average intensity of these landfalling typhoons is expected to be relatively strong, thereby promoting the spread and prevalence of southern rust across the Huanghuai and Haihe regions.

　Source: Pesticide Express