Studies On The Effects Of Bt Cotton On Biological And Ecological Characteristics Of Phenacoccus Solenopsis Tinsley

The safety of Bt cotton has attracted much attention in recent years, Phenacoccus solenopsis Tinsley has become a major pest which was serious damage to cotton. This paper studies on the solenopsis mealybug feeding on Bt cotton and normal cotton showed the differences in biological habits, behavioral ecology, laboratory population life table, the interaction between host and predators (Harmonia axyridis), and the harmfulness. To confirm whether the Bt cotton can directly or indirectly affect on Solenopsis mealybug.The results showed that:solenopsis mealybug feeding on Bt cotton which at seedling stage, vegetative stage or reproductive stage, there were no significant differences on the morphological characteristics, female ratio, behavioral ecology, the development duration of Harmonia axyridis, and the predation. But it was showed a significant difference on some biological habits, such as the development duration of the continuous generation larvae, the developmental duration of individual instars, the fecundity of female adult, and the life of male/female adult. In the laboratory population life table, there were no significant differences on the survival of every development larvae or generation, the female ratio, and index of population trend.Solenopsis mealybug feeding on the different varieties cotton might not directly influence on the development duration of Harmonia axyridis, also might not directly affect the predating numbers of Harmonia axyridis. But, the predating numbers of Harmonia axyridis feeding on solenopsis mealybug which was parasites in Bt cotton, was higher than the control group during a day. The Predation efficiency was also higher than the control group.Bt cotton showed some extent resistance to solenopsis mealybug. When the1st instar nymphs’population density was less than120, the seedling stage Bt cotton’s tolerance degree was higher than the normal cotton’s. When the1st instar nymphs’ population density was less than360, the vegetative stage Bt cotton’s tolerance degree was higher than normal cotton’s. However, if the damage cumulative time was longer than the minimum time of solenopsis mealybug’s one generation required, there were no significant difference between Bt cotton and normal cotton, they suffered serious damage and dead at a rapid speed.