| The regularity, characteristic, and degree of pest imperilment of Dewu in Zhongshan district(middle-high altitude) and Lemin town in Panxian district (middle-low altitude) was researched in this thesis. And by analysing the similarities and differences of different pests in the two regions, this thesis bringing forward the control efficienticy from the views of production and ecology.1. The first part covered the morphological characteristic, regularity of onset, characteristic and degree imperilment of blank cutworm, Asiatic corn borer and armyworm on corn main pest.2. The major onseting period of blank cutworm is between middle and later of April and May in Dewu region. Often it would take 60 to 66 days of one generation from egg to larva, pupa, and imago in Dewu region.3. There isn't obvious selectivity in blank cutworm imperilment, the onseting quantity and imperilling degree is similar on different crops. It's more serious in the field of invasion of weeds and corn intercrop potato than single cropping of corn, and the field of forecrop green manure is more serious than single cropping. Imperilment degree of black cutworm is very serious in both high altitude region as Dewu (1780 meters) and low altitude region as Lemin (1450 meters). The imperilment degree in two regions have no obvious differences.4. The imperilment of second generation armyworm is very serious in both high altitude region of Dewu and low altitude of Lemen town. The onset period of larva is between the early and middle of June and July. The onseting time of Lemin was earlier than Dewu for 3 to 5 days. It will take 51 to 63 days for second generetion of armyworm to develop from egg to larva, pupa, and imago in Dewu region.5. There is evidently difference of armyworm imperilment degree in different altitude. High altitude region is more srious than low region. The armyworm imperilment degree varies in different crops. The field planted wheat as forcrop is serious. Also, different levels of cultivation management have evident effects on the imperilment degree of armyworms. For instance, the fields of rough management and bad crop growing suffered more serious imperilment than those of high quality management, intensive cultivation and good crop growing way.6. The first generation of Asiatic corn borer is onseting between later of May and early of July in Lemin (1450 meters). And in Dewu the time is between the early of June and the early and middle of July. The second generation of Asiatic corn borer appeared in the later of July in Lemin and in the early of Augest in Dewu. It will take 56 to 63 days for the frist generetion of Asiatic corn borer to develop from egg to larva, pupa, and imago in Dewu region.7. The primary imperilment period of first gemeration of Asiatic corn borer is shooting stage. And the heading stage, grain filling stage in early sowing corn and belling stage in late sowing cron is disserved by the second generation. The imperilment degree of second generation is more serious than frist generation.8. The best way for the prevention of black cutworm is to spray on early larva and to trap and kill with poison bait in late larva. The average of control efficiency reaches 90.33 percent. The worst way is to trap and kill with poison bait in late larva, reaching 57.86 percent in avarage.9. The best way for prevention of Asiatic corn borer is using granule in belling stage combine with spray in heading stage, could reach 92.58 percent of control efficenticy, and the worst control efficiency is to just spray in the heading stage, with only 73.78 percent of efficiency.10. Using four types of pesticides to spray in early onset period of larva in this research and find all the emendation rate of reducing number reached above 94 percent, so the control efficenticy is good. |
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