| Effects of Bacillus thuringiensis crystal protein and transgenic B. thuringiensis cotton on the parasitoid, Campoketis chloridae Uchida (Hymenoptera: Ichneumonidae), and comparative impacts of the univalent and bivalent transgenic cottons on main cotton pests and their natural enemies in fields were studied. Results were showed as followed:1. The artificial diets containing B. thuringiensis protein in higher concentration could kill the majority of C. chloridae, main because its host-cotton bollworm larvae had a higher mortality. Effects of sub-lethal dose of B. thuringiensis on approximate larval weight, larval development period, pupal weight and development period . adult weight of and adult longevity of C. chlorideae were significantly different from the control, although B. thuringiensis in sub-lethal dose condition might not cause parasitoid death.2. The liquid artificial diets containing concentration of 0 g/g (the control), 2.5 g/g and 25 g/g were fed with adult female and male parasitoid and adult longevity was investigated and recorded. Analytical results revealed that B. thuringiensis have no direct effects on parasitoid compared with the control.3. Host larvae were fed with transgenic B. thuringiensis cotton leaves and the control cotton leaves for different hours before and after being stung by C. chloridae. Effect of transgenic cotton on approximate larval weight, larval development period, pupal weight and development periods adult weight of and adult longevity of C. chlorideae were checked. Results could be drawn that when feeding time before and after being stung were prolonged, developmental characters of parasitoid were notably different from the control.4. The univalent and bivalent transgenic cotton were excellently resistant to cotton bollworm in the former period of cotton growth and development. Moreover, two insect-resistant cottons had on significant difference. But in the latter period, resistance of bivalent cotton was significantly stronger than univalent one. The population numbers of majority of non-target pests in transgenic cotton fields were more than in the common cotton field. However, the population of the majority of natural enemies in transgenic cotton fields were less than in the control field. These demonstrated the results: Damages resulting from non-target pests were more serious and numbers of predatory natural enemies were lower in transgenic fields than in common field. The population of piercing-sucking pests in transgenic fields were significantly higher than in common field; With regard to each piercing -sucking pest, number in bivalent and univalent transgenic cotton fields were different. The population of two parasitic enemies of Cotton aphids changed with the number of aphids and had no notable difference in bivalent and univalent cotton fields. Effects of transgenic cotton on parasitic natural enemies of lepidoptera were significant.5. The dominant pests in the univalent and bivalent cotton fields were more different from the ones in common cotton field. Cotton bollworm was not only dominant pest in transgenic cotton, Cotton aphid(Aphis gossypii Glover), Bemisia tabaci Gennadius, Ejnpoaca biguttula Shiraki had become the dominant pests. The dominant natural enemy populations had no changed in transgenic cottons compared with common cotton.6. The diversity index and the evenness were also lower in the univalent and bivalent cotton fields than in the control one, but the dominant concentration were higher in the two transgenic cotton fields than in the common one. So stability was better in the control cotton field than in the univalent and bivalent cotton ones. The bivalent cotton had higher the diversity index and the evenness than the univalent cotton. Therefore, the former had better stability.7. The principal component analyses were carried out by SPSS. There were the same conclusion: Eringonidium graminicola Sundevall and Orius minutus Linnaeus were dominant natural enemies in the former period of the growth of cotton. Chry...
|
PDF Full Text Request