Forecast of occurrence trend of diseases and pests in Maize in the middle and late stage
By: Date: 2022-07-29 Categories: foodtechnology Tags: ,
According to the current occurrence base of diseases and insect pests, the regional layout and planting mode of corn, combined with the comprehensive analysis of future weather conditions, it is expected that the overall occurrence of diseases and insect pests in the middle and late stages of this year will be more serious, with pests slightly lighter than last year and diseases heavier than last year. Migratory pests such as Spodoptera graminearum, armyworm of the third generation and cotton bollworm pose a great threat to maize production, and diseases such as large leaf spot, brown spot and southern rust are more likely to occur in local areas; In the peak period of damage, most of the northern corn producing areas are from late July to early September, and the southern corn producing areas can last until the end of October.
 
I. occurrence trend
 
It is estimated that there will be 810 million mu of pests and diseases, 530 million mu of pests and 280 million mu of diseases in the middle and late stage of Maize in China, with a year-on-year decrease of 4%, 7%and an increase of 4%respectively.
 
Spodoptera graminearum mainly endangers summer and Autumn Sown corn in southwest, South China and Jiangnan, and occurs heavily in annual breeding areas such as Yunnan, Guangxi and Guangdong, and occurs locally; It occurs moderately in the south of the Yangtze River and the middle and lower reaches of the Yangtze River, with partial emphasis; The Yellow Huaihe River and Northwest China are light, and the North China is dotted; The possibility of adult migration and sporadic larval occurrence is greater in the south of Northeast China; It is estimated that the area of occurrence nationwide will exceed 30million mu. The occurrence of the third generation armyworm is generally moderate, and there will be high-density concentrated damage areas in the northwest, northeast, North China, Huang Huai and southwest regions, with an area of 25million mu. The second generation of meadow moth occurs moderately in Inner Mongolia and its surrounding areas, and the first generation of adults and the second generation of larvae occur 10million Mu times. The third and fourth generations of cotton bollworm occur moderately in the Huang Huai Hai and Northwest China, with an area of 65million mu. Corn borer occurs in some parts of the Huang Huai River, moderately in most parts of North China and southwest China, and 180 million mu times in the second and third generations. Aphids occur moderately in Northeast, North and Northwest China, with an area of 55 million mu. The double spotted leaf beetle occurs moderately in parts of North China and Northeast China, with an occurrence of 35 million mu. Tetranychus mites occur moderately in some areas such as northwest and North China, with an occurrence of 20million mu.
 
The disease mainly occurs in Northeast and North China, and moderately in Huang Huai and southwest China, with an area of 80million mu; Southern rust is more likely to be prevalent in the Huang Huai sea, with an area of 65million mu; Small spot disease occurs moderately in the Huang Huai River and most of the southwest, with an area of 35 million mu; Brown spot disease occurs moderately in the Huanghuaihai sea and heavily in Hebei, with an area of 33million mu; Anthrax in the North occurs moderately in the north of Northeast China, with an area of 10million mu. In addition, ear rot, stem rot, Curvularia leaf spot, sheath blight, gray spot and other diseases will also cause certain harm.
 
II. Prediction basis
 
(I) high insect source base
 
As of July 14, 24.71 million mu of grassland Spodoptera occurred in 653 counties in 20 provinces; Recently, four new larval provinces in Henan, Shaanxi, Gansu and Hebei have been added. Among them, the elderly larva was found in Fengnan District of Tangshan, Hebei Province on July 11, and the migration time was about 1 month earlier than the previous three years. This week, the average number of 100 larvae in various places is less than 10, but the number of 100 larvae in some fields in Mangshi, Gengma, Gaozhou, Guangdong and other places is more than 100.
 
As of July 14, the second generation armyworm has occurred in 20million mu in the northwest, Huang Huai, North China, northeast and southwest, with a year-on-year decrease of 42.8%. The occurrence degree is lighter than that of the previous year and all the year round. Only some areas of Liaoning and Jilin have high-density concentrated hazardous fields. At present, the harm of the second generation armyworm has basically ended, and the number of residual insects in Yunnan and Inner Mongolia is 7.2 head /m2 and 1.8 head /m2 respectively, and less than 1 head /m2 in most other regions.
 
The first generation larvae of meadow moth only occur in Inner Mongolia, Hebei and other places. The population density of Wuchuan County, Liangcheng County, Fengzhen City, Inner Mongolia and Kangbao County, Hebei is relatively high. Among them, the maximum population of corn in Wuchuan county is 2000 heads/100 plants, and the maximum population of weeds in Kangbao County is 232 heads/m2.
 
The base number of corn borer continues to decline year by year. The average number of one generation larvae per 100 plants is 23 in Yunnan, 6.7 in Xinjiang and Hubei, and less than 5 in other provinces.
 
(II) the growth period and planting method of corn are suitable for the occurrence of diseases and pests
 
At present, corn in Northeast, northwest and other places is mostly in the stage from bell mouth to tassel stage, corn in Huang Huaihai and other places is mostly in the jointing stage, corn in the south is planted alternately, and corn growth periods are different in summer and autumn, which is suitable for the occurrence of Spodoptera xylostella. Continuous planting of corn, with tall plants and closed fields in the later stage, is conducive to the occurrence of diseases and pests. Some plots with extensive management and many weeds are particularly conducive to the centralized spawning of armyworm and meadow moth. The strip compound planting of soybean and corn is conducive to the transformation of polyphagous pests such as meadow moth, cotton bollworm, leaf mite, double spotted leaf beetle, etc. At the same time, in some areas, diseases such as large leaf spot and brown spot occur year after year, and the proportion of straw returning to the field is large, which is conducive to the accumulation of pathogenic bacteria.
 
(III) meteorological conditions are favorable for the occurrence of corn diseases and pests in most regions
 
According to the prediction of the National Climate Center, from July to August, there will be more precipitation in the southeast of Northeast China, North China, most of East China, North Central China, South China, east northwest, southwest and other places, which is conducive to the occurrence of Spodoptera graminearum, armyworm, meadow moth and epidemic diseases; The temperature in Xinjiang and Central East China is 1-2 ℃ higher and the precipitation is 20-50%less, which is beneficial to the occurrence of drought loving pests such as cotton bollworm, aphid and spider mite. In addition, the possibility of a northward typhoon in midsummer, which will significantly affect East China and the north, is conducive to the epidemic harm of Southern rust in the Huang Huai Hai region, and will promote the northward migration of Spodoptera graminearum.