On July 27-28, the National Agricultural Technology Center held a corn disease and insect meeting chamber of commerce in Jilin City, Jilin Province, and the monitoring and reporting technicians and corn industry system experts of 24 corn producing provinces (autonomous regions and cities) made predictions on the occurrence trend of diseases and insects in the middle and late stages of corn in 2017 based on the current base of occurrence of corn diseases and insect pests, corn cultivation methods and crop layout, combined with future climate trend predictions and other factors.
First, the occurrence of diseases and insect pests in the early stage of corn
The pre-maize diseases and insects are mainly the first generation of corn borer, the second generation of armyworms, the second generation of cotton bollworms, the two-point nocturnal moth, underground pests, thrips and blight, which are generally light, and the degree is close to that of previous years, with an area of 265 million mu, of which 240 million mu of corn insect pests occur and 24.8 million mu of corn diseases occur. A generation of corn borer occurs more heavily in Xinjiang, Heilongjiang, western Liaoning, central and western Jilin and eastern Inner Mongolia, and most areas in other parts of northeast China, north China, Huanghuai, and southwest China are mild to moderate. At present, most areas have passed the first generation of harm period, the second generation of corn borer has begun to be harmful, and Shandong and other places have occurred more seriously. The overall occurrence of second-generation armyworm is moderate, the occurrence area is larger than that in 2015 and 2016, the degree of occurrence in some areas is heavier than the same period in the past four years, and high-density fields appear in Shandong, Henan, Shaanxi, Yunnan, Inner Mongolia and Heilongjiang, with the highest number of 100 insects in various places being 120-900 heads. It occurs moderately in Hebei, with heavy occurrence in local fields and light occurrence in other parts of the Huang-Huai-Hai Region. The incidence of second-generation cotton bollworm in North China, Huanghuai and Northwest China is significantly heavier than in previous years, among which Hebei, Shandong, Gansu, Ningxia and other places are more serious. Thrips occur more heavily in Shandong, Tianjin and north-central Hebei. Underground pests occur heavily in parts of northeast and northern China, and Chifeng in Inner Mongolia is seriously damaged. Double-spotted long-planted fluorescent leaf beetles occur more heavily in Heilongjiang, northern Shanxi, eastern Inner Mongolia, and northern Xinjiang. The beet nocturnal moth has increased significantly in Huanghuaihai and Inner Mongolia. Brown-footed horned horbiformis occurs in Hebei and Beijing on a mild to moderate basis. Maize large spot disease, small spot disease, brown spot disease, striped blight, curvular leaf spot disease, powdery mildew, silk smut disease and other diseases in the northeast and northwest spring maize areas and the Huang-Huai-Hai summer maize area first appeared late, and the incidence was less than usual.
Second, the trend of diseases and insect pests in the middle and late stages of corn
It is expected that the overall occurrence of diseases and insect pests in the middle and late stages of corn this year will be heavier than that of the previous year, and the end of July to the end of August will be the peak period for various diseases and insects.
(1) The type and area of occurrence
In the middle and late stages of maize, the diseases and insects are mainly drill moths, leaf-eating, stinging pests and leaf diseases, and corn borers, cotton bollworms, aphids, large spot diseases, small spot diseases and brown spot diseases are more common and more harmful; leaf mites, double-spotted long tarsal fireflies, curved leaf spot disease, silk smut disease, powdery mildew, striated blight, stem rot, gray spot disease, etc. cause certain harm in some areas. It is estimated that 869 million mu of diseases and insect pests will occur in the middle and late stages of maize, 592 million mu of insect pests, and 277 million mu of diseases (see Table 1 for the estimated area and key areas of each disease and insect).
(2) Degree of occurrence and key areas
1. Drill moth pest. The first generation of corn borer occurs in Heilongjiang and northeast Inner Mongolia, where the second generation occurs more heavily in central and western Liaoning and Jilin, western Xinjiang and eastern Inner Mongolia, and in other regions, and occurs in other regions with light to moderate occurrence; the third generation occurs more heavily in Henan and Anhui, and occurs in other regions with light to moderate. The third and fourth generations of cotton bollworms occur more heavily in the Huang-Huai-Hai and northwest regions, and the peach borer and the large borer are aggravated in some areas.
2. Leaf-eating pests. Three generations of armyworms occur in the northeast, north China, Huanghuai, southwest and northwest, and in Liaoning, Jilin, Heilongjiang, Inner Mongolia, Shandong, Shaanxi, Shanxi, Henan and Yunnan, and some areas with high moths and suitable climate have the possibility of high-density plots;
3. Stinging pests. Aphids occur moderately in most parts of Northeast China, North China, Northwest China and Huanghuai, and more frequently in arid areas of Northeast, North China and Northwest China, leaf mites occur moderately in most areas of Northwest China, and Ningxia, Gansu and central and western Inner Mongolia.
4. Diseases. Large spot disease occurs more heavily in the eastern part of the northeast, moderate in the central and western parts of the northeast and northern North China; small spot disease occurs moderately in Huanghuai and most of the southwest and other regions are mild; southern rust is likely to occur more heavily in southern Huanghuai and other places; curvular leaf spot disease and brown spot disease occur more lightly in most parts of the Huang-Huai-Hai Sea; gray spot disease occurs moderately in the mountains of southwest China and the eastern part of the northeast; striated blight occurs more heavily in most of the southwest; and stem rot is at great risk of heavy occurrence in the Huang-Huai-Hai Sea. In addition, diseases such as powdery mildew and ear rot will also cause certain harms in local areas.
2. Basis for forecasting
(1) In some areas, the base of second-generation armyworm and cotton bollworm is high, and the base of corn borer and disease is low
In July, the black light lamps monitored the number of adult armyworms of the second generation, and the average single lamp of 19 monitoring and reporting points in 11 cities such as Heze, Yantai and Jinan in Shandong Province was 129 moths, which was 2.1 times that of the previous year, and the cumulative number of moths in Wenshang and Yuncheng with high insect volume was 525 and 476 respectively, and the peak daily moths were 105 and 172, respectively. The cumulative number of moths in Yongcheng, Yichuan and Yancheng in Henan was 198, 267 and 348 respectively. The total number of moths in Hebei Daimyo is 673, and the number of moths is 131 on July 17. The cumulative number of moths in Ruicheng, Shanxi Is 343. Liaoning Shenyang, Faku, Kaiyuan, Zhangwu single-lamp single-day maximum lure moths 18-75, higher than the same period last year.
The cumulative moths in Xingping, Shaanxi, Shuangcheng, Heilongjiang, and Changdao, Shandong were monitored by high-altitude monitoring lamps in various places
There were 798 heads, 580 heads and 278 heads, and the peak daily moth volume was 146 heads, 169 heads and 140 heads, which was the highest among the monitoring points; the cumulative moth volume and peak in the northeast region were higher than that of the previous year, except for the Long Island point in Shandong, the cumulative moth volume and peak in the Huanghuai and North China monitoring points were lower than the same period last year.
The second-generation cotton bollworm is on the high base in north China, northwest China and most of The Huanghuai, and occurs in crops such as corn, peanuts, soybeans, vegetables, Chinese medicinal materials, and oil sunflowers, and the maximum is 15-30 heads of 100 corn plants in hebei re-issued plots, with a maximum of 46 heads. Provinces (autonomous regions, municipalities) count the average number of 100 live insects in a generation of corn borers, 50 in Guizhou, 47 in Heilongjiang, 31 in Chongqing, 10-20 in Jilin, Hunan, Jiangsu and Liaoning, and other provinces are below 10, and most of the bases are low.
At present, the leaf disease of corn has begun to occur in various places and showed a gradual aggravation trend. In the early drought of maize large spot disease in northeast China, Shanxi and other places, the source base of the disease was reduced, and the initial peak period was delayed by nearly one month than the year in which it occurred heavily.
(2) Maize varieties and planting systems are conducive to the occurrence of a variety of diseases and insect pests
There are few varieties of disease and insect resistance in corn planting in China, and the continuous planting method of corn in the north is conducive to the occurrence of diseases and insects in a large area. Some extensively managed plots are conducive to the occurrence of concentrated occurrence of armyworms. At the same time, the plants are tall and the fields are closed in the late stage of corn growth, which makes it difficult to prevent and control corn diseases and insect pests, resulting in aggravation of pests and diseases.
(3) Future meteorological conditions are favorable for the occurrence of corn diseases and insects in most areas
According to the forecast of the National Climate Center, in August, the eastern part of the northeast region, the southern part of the southwest region, the northern part of Xinjiang and Jiangnan and other places have more precipitation, which is conducive to the occurrence of wet-loving diseases and insects such as corn borer, armyworm, large spot disease, small spot disease, brown spot disease, curvular leaf spot disease in the above areas. Precipitation in central Inner Mongolia, most of North China, and northern Huanghuai is 20%-50%, which is conducive to the occurrence of drought-loving pests such as cotton bollworms, aphids, leaf mites, and double-spotted long-planted fireflies in these areas. It is expected that 1 to 2 tropical cyclones will make landfall in August or significantly affect China, which will help the spread of southern rust in southern Huanghuai.