| In this article, the harmful insects on the sweet corn in the Nanning city, Guangxi Province were taken as the objective of the study, of which their occurrence, species, population dynamics, the kinds of natural enemies, and the effect of the prevention and cure technique to the main pest by using non-chemical pesticides etc. The main results were listed as follows.1). The harmful insects' species occurred on sweet corn. There were 6 orders which include 28 families and 77 species, among which Lepidoptera has 24 species, Orthoptera, 19 species, Coleopteran, 10 species and Hemiptera, 9 species, And there were 1 order of Acariformes, which includes 1 family and 2 species. All of these different species had been reported in the past time.2). The community structure of the pests on the sweet corn. Both the diversity index (H) and the evenness index (J) of community were higher, but the centrality probability index(λ)and the dominant index (D) were lower. The results showed that there were little differentiation between the number of the different species and their distributions also were even. The main dominant species are the Asian corn borer Ostrinia furnacalis Guenee, but it's dominant index was no clear. 3). The varieties and the season fluctuation of population in the corn field. The species of fluctuation of them was the pattern of single peak. During the first ten days of March, April, May and June in 2004, there were 3 species, 5-6species, 7 species and 12 species respectively on the Spring sweet corn, which showed the summit was the beginning of June. In the same period in 2005, the same species were discovered, the number of which were 4 species, 4-5 species, 8 species, 3 species respectively, but the summit was the middle of May. During August, September, October, and November in 2004, 2 species, 3-4 species, 4 species, 5 species were respectively discoved on the Autumn sweet corn, and the summit was the later of October and the beginning of November. But in 2005 there were 6 insects species in September, and 2-3 species in the rest month, Ialso discoveried the summit was the later of September.The main species of order on the spring sweet corn in 2004 were: Leucania separata Walker>Ostrinia furnacalis Guenee>Agrotis ypsilon (Rottemberg)>Prodenia litura Fabricius>Euproctis latifascia Walker>Sesamia inferens Walker. And the main species of order on the autumn sweet corn in 2004 were: the Asian corn borer Ostrinia furnacalis Guenee>Leucania separata walker>Agrotis ypsilon Rottemberg>Prodenia litura Fabricius>Euproctis latifascia walker. I also found that the main species in order on the spring sweet corn in 2005 were: the Asian corn borer Ostrinia furnacalis Guenee>Euproctis latifascia Walker>Leucania separarta Walker>Agrotis ypsilon Rottemberg>Amsacta lactinea Cramer>Prodenia litura Fabricius>Sesamia inferens Walker. And the main species in order on the autumn sweet corn in 2005 were: the Asian corn borer Ostriniafurnacalis Guenee>Leucania separata Walker>Euproctis latifascia Walker>Sesamia inferens Walker.4). The different pests of weed species on the sweet corn. The main weed species of experimental corn field were 8 families and 24 species, the fomer included Graminacea, 7species, compositaceae, 6 species and Cyperaceae, 4 species. There were different harmful insects in the different weed species on the sweet corn. They are Locusta migratoria manilensis Meyen, Oxya chinensis (Thunberg), Atractomorpha sinensis I. Bolivar, Euproctis sp's larve and Nezara viridula. Fabricius5). The main natural enemies of the harmful insects of the sweet corn. There were 13 families and 26 species in the experimental field occurred, among which were Trichogramma ostriniae Pang et Chen, Coccinella sp. Chrysopa sinica, C septempunctata and C phyllochroma etc.6). The main effect of the prevention and cure technique to the main pest by using non-chemical pesticides.①Trapping lamp: 5 orders, 17 families and 35 species of insects were trapped during the spring and autumn in 2005, among which were killed were: Asian corn borer Ostrinia furnacalis Guenee>Leucania separata Walker>Sesamia inferens Walker>Cnaphalocrocis medinalis Guenee>Prodenia litura Fabricius>Nilaparvata lugens Stal>Nilaparvata sp.>Agrotis ypsilon Rottemberg>Rhopalosiphum maidis Fitch>Laphygma exigua Hubner>Spilartia obliqua Walker. But many natural enemies of harmful insects were also attracted. They were: Leis oxyridis (Pall as), Coccinella sp, Prophyleae sp, Geocoris sp, Paragus sp, and Lasiopticus p, etc. The number of the harmful insects attracted by the trapping lamp wa more than that by the black light insect number, which showed that the use of trapping lamp was more effective and safer than the traditional back lamp in trapping pest. (2) The harmful insects trapped by the yellow plaque were 11 species. The more species pest are Rhopalosiphum maidis Fitch, Leucania separata Walker, Cnaphalocrocis medinalis Guenee, Nilaparvata lugens Stal and Asian borer Ostrinia furnacalis Guenee.③7 days after the application of Bt, the decrease rate of Leucania separata Walker larva and the Euproctis latifascia Walker were respectively 57.42%, 44.68% and 65.84% 73.47%. And the decrease rate of Prodenia litura Fabricius larva and the Cnaphalocrosis medinalis Guenee were respectively 76.46% and 38.46%.④Integrate controlling the main pests on the sweet com by using the trapping lamp, yellow plaque and Bt could make the Ostrinia furnacalis Guenee larva on 100 plants of com decrease about 90.7% and 83.33%, the Leucania separata Walker larva on 100 plants of corn decrease about 82.35% and 100% and also made the puceron Rhopalosiphum maidis Fitch on 100 plants decrease about 43.15% and 57.74%. The proportion of parasitism of the Trichogramma ostriniae on the Ostrinia furnacalis Guenee larva and corpusculum were respectively about 23.51% and 49.55% in the experimental field, and the population intensity of the other natural enemy, such as Leis oxyridis (Pall as), Coccinella sp, Propylaca sp etc, increased by a little.
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