Study On Biology Characteristics And Resistance Selection Of Imidacloprid On Harmonia Axyridis Pallas

Harmonia axyridis (Pallas) (Coleoptera, Coccinellidae), is a kind of important predators on extractive industry. Due to large appetite, high fecundity, adaptability and many generations annually, Harmornia axyridi (Pallas) is one of the important predatory natural enemies in agriculture system. In this paper, the biology characteristics and resistance selection of Harmornia axyridi (Pallas) were investigated.1. Growth and development of Harmonias axyridis (Pallas) feed on Chaitophorus populeti (Panzer), Rhopalosiphum padi (Linnaeus), Lipaphis erysimi (Kalteback), Hyalopterus amygdale(Blanchard), and Aphis gossypii (Glover) were studied, the result showed that an average of development duration were 30.5d, 23.8d, 25.3d, 26.5d, and 23.8d, respectively. An average of lay-egg duration were 87d, 34d, 56d, 52d, and 38d. Each female laid an average of 1238 eggs, 855 eggs, 1835 eggs, 1396 eggs and 710 eggs. The weight of female was 21.3g, 26.1g, 27.3g, 30.9g, and 25.4g, respectively. The weight of male was 21.6g, 23.3g, 25.4g, 29.1g, and 23.3g. The innate capacity for increase was 0.068/d, 0.132/d, 0.112/d, 0.103/d, and 0.102/d. In summary, Lipaphis erysimi (Kalteback) and Hyalopterus amygdale(Blanchard) were the better food for development of Harmonias axyridis (Pallas) than the other three.2. The functional response of Harmonias axyridis (Pallas) predating on Chaitophorus populeti (Panzer), Rhopalosiphum padi (Linnaeus) and Lipaphis erysimi (Kalteback) were investigated in the laboratory. The results showed that the predation capacity of different instar (form) of Harmonias axyridis (Pallas) has biggish diversity. The daily predation numbers ascended as the age increased. The 1st and 2nd instar preyed on 13.6～17.6 capita, the 3rd instar preyed on 57.3～67.8 capita, the 4th instar was 106.8～119.2 capita, and the adult preyed on 96.8～109.2 capita.. The predation number of Harmonias axyridis (Pallas) ascended with the increasing of the density of aphids. The functional response of the Harmonia axyridis (Pallas) to aphids was simulated with models of Holling-â…¡. The research will provide the theoretical basis for controlling the aphids using Harmonia axyridis (Pallas).3. Selection of a susceptible strain of Harmonias axyridis (Pallas) with imidacloprid resulted in a moderate level resistance. The result showed that the resistance selection of Harmonias axyridis (Pallas) was in a low resistant level at present. After 11 generations of selection, the resistance ratios of Harmonias axyridis (Pallas) to imidacloprid was 9.67-fold compared with that of the unselected parental strain. From F₁ to F₅, the resistance ratios ascended from 0.0329μg/head to 0.1178μg/head, which was ascending much slowly. From F₈ to F₁₁, the resistance ratios ascended from 0.1693μg/head to 0.1693μg/head, which was ascending much quickly.4. Studies on resistance selection and mechanisms of Harmonias axyridis (Pallas) to imidacloprid were also carried out, the result showed the difference of CarE activity(0.79μmol·mg^-1·min^-1 and 0.83μmol·mg^-1·min^-1) and GSTs activity (2.83 OD·mg^-1·min^-1 and 2.62 OD·mg^-1·min^-1) between the strain unselected and the strain selected by imidacloprid was not significant, whereas the activities of AchE activity (0.32μmol·mg^-1·min^-1å’Œ1.56μmol·mg^-1·min^-1)was significantly different. This indicated that AchE might be involved in resistance mechanism of Harmonias axyridis (Pallas).