Structure And Dynamic Of Insect Communitie In Spring-sowing Rape Field And Resistance Of Its Varieties To Rape Aphids

Rape is the most important economic crop, and often attacked by many pests in Gansu.Insect community structure and functions in spring sowing rape and the resistance of different spring sowing rape varieties to aphids were studied with the principles and methods of community ecology and insect resistance of crop to meet the need of rape SPM (Sustainable Pest Management) at Kangle and Lintan in 2007. The results were as follows:1 The survey of insect community structure in the spring sowing rape field1.1 Insect community structure in the spring sowing rape field Of all insect species, 38 species were rape pests, 23 species were natural enemies (22 predator species and 1 parasitoid species), 11 species were natural insect. During investigation, r-tacting insects of them were still dominant in population. The orders with high species richness were Coleoptera (47 species), Diptera (6 species) and Lepidoptera (6 species).The families with highest species richness were Chrysomelidae (9 species) and Coccinellidae (8 species).In the spring sowing rape field, the orders with high relative individual abundance were Homoptera (95.48%) and Diptera (2.75 %); the families with high relative individual abundance were Aphididae (95.47%) and Agromyzidae (1.92%).In the spring sowing rape field of Kangle, the dominant rape insect species were Myzus persicae(Sulzer), Lipaphis erysimi(Kaltenbach) and Brevicoryne brassicae (L.), frequent rape insect species was Phytomyza atricornis Meigen; in the spring sowing rape field of Lintan ,the dominant insect species was Myzus persicae(Sulzer), abundant insect species was Lipaphis erysimi(Kaltenbach), frequent insect species were Brevicoryne brassicae(L.), Meligethes aeneus abricius, Ceutorhynchus quadridens (Panzer) and Phytomyza atricornis Meigen.1.2 Characteristics of insect community in the spring sowing rape fields.The richness, diversity index, evenness index and dominance indexes of pest and natural enemy sub-communities all changed with time. The natural enemy sub-community had a similar dynamics of diversity, dominance and evenness with pest sub-community. The highest diversity and evenness indexes of pest sub-community were in the seedling stage and maturaty stage and the lowest of them was in the blooming stage in Kangle. The dominance indexes of pest in Lintan were still high and all above 0.5 through the whole spring sowing rape growth stage. The diversity indexes of the pest sub-community were lower and less than 2 after the buds stage.1.3 Clustering analysis of insect community in the spring sowing rape field Based on the component structure of insect communities and rape developmental period, the dynamics of pest and natural enemy sub-communities communities in the spring sowing rape field were divided by the method of fuzzy clustering, and the community characteristics and control strategies in different periods were given. The results showed that both of pest and natural enemy sub-communities could be grouped into 3 clusters in Kangle, and natural enemy and pest sub-communities of Lintan could be grouped into 2 and 3 clusters.This clustering reflected the complexity of the community structures.1.4 Niches Analysis of rape aphids To understand the interspecies relationship among common rape aphids species, the niche breadth and overlap of Myzus persicae (Sulzer), Lipaphis erysimi (Kaltenbach) and Brevicoryne brassicae (Linnaeus)on spring sowing rape, were measured based on the survey data in Kangle and Lintan. The results indicated that M. persicae could use more host resources than other two species, and had the greatest temporal niche. However, in Kangle B. brassicae and L. erysimi overlapped mostly in both temporal and tempo -spatial niches than M. persicae and L. erysimi.2 Resistances of spring sowing rape varieties to rape aphids28 spring sowing rape cultivars were screened to select genetic resources resistant to aphid by the method of aphid index. The result showed that the resistances of varieties were significantly different and classified into five groups: one variety behaved highly resistant, which was 06 Guan chunyun No.3; 17 moderately resistant varieties, which was 06 Jingza No.32, 06 Jingza No.20 etc; six lowly resistant ones, which was Menyuan, Huaxie No.1, 06jinza No.18 etc; three susceptive varieties, which was Qinza No.2, Qingyou No.14, 06jingza No.21; Mianyou No.14 was high susceptive variety.