Abstract:

The aim is to clarify the biological control potential of three dominant natural enemies, Hippodamia variegata, Coccinella septempunctata L. and Megalocaria dilatata, against Frankliniella occidentalis and Bemisia tabaci. Under indoor conditions, three species of ladybugs were fed with different benefit-to-harm ratios using field collected F. occidentalis and B. tabaci nymphs, the density of F. occidentalis and the number of B. tabaci nymphs with feeding marks was recorded, as well as the proportion of their adults that had emerged, for each treatment during the experiment. The results showed that after 3 days of feeding and treatment of F. occidentalis, the control ability of the three adult ladybugs and larvae on F. occidentalis was: adults of H. variegata>third instar larvae of C. septempunctata L.>adults of C. septempunctata L.>third instar larvae of M. dilatate> third instar larvae of larvae of H. variegata> adults of M. dilatata, among which the adult H. variegata had the highest control effect on F. occidentalis, reaching 48.35%. After 3 days of feeding and treatment of B. tabaci nymphs, the number of bite marks of young nymphs in the third-instar larvae treatment group of M. dilatata was 2.61%, which was significantly higher than that in the control group, and there was no significant difference between the other treatments. There was no significant difference in the adult plumbing rate of B.tabaci between the treatment groups. This study showed that the adults of H. variegata had a high control effect on F. occidentalis, and the third instar larvae of M. dilatate had a certain feeding tendency against the young nymphs of B. tabaci nymphs, and the three kinds of ladybirds did not have feeding tendency to the old nymphs of B. tabaci nymphs.

Key words: Frankliniella occidentalis, Bemisia tabaci, Hippodamia variegate, Coccinella septempunctata, Megalocaria dilatate, biological control, benefit-to-harm ratio, feeding preference