Functional response of coccinelid, Harmonia axyridis Pallas on Crapemyrtle aphid, Tinocallis kahawaluokalani Kirkaldy in laboratory condition

Background and Objectives Aphids are one of the major pests in ornamental plants may cause damage to plants directly by sucking their sap, and indirectly by injecting toxic salivary secretions, transmitting pathogens, attracting ants and favoring the development of sooty-mold. Crapemyrtle aphid, Tinocallis kahawaluokalani Kirkaldy, currently is considered the most serious pest of ornamental woody plant, Lagerstroemia spp. and produce large amounts of honeydew while feeding. T. kahawaluokalani causes premature drop of leaves, decline of summer flowering and reduces the commercial market. The multicolored Asian ladybird, Harmonia axyridis Pallas, is capable of eliminating T. kahawaluokalani populations on crape myrtle plants. There is no data about the predatory behavior of H. axyridis on T. kahawaluokalani. So, functional response of third and fourth larval instars, and females and males of H. axyridis to T. kahawaluokalani was studied in the laboratory condition. Materials and Methods Adults of H. axyridis and nymphs of T. kahawaluokalani were collected from Crapemyrtle plants in Mazandaran province (North of Iran). They were reared together on the Crapemyrtle leaves in the laboratory conditions (25± 2 °C, 60%± 10% RH and a photoperiod of 16:8 h L: D) h. Prey densities were 5, 10, 20, 30, 60, 80 and 120 aphids for third and fourth larval instars, and adult females and males. The number of prey consumed by each stage of the predator was recorded at each density after 24 hours. The type of the functional response was determined by logistic regression analysis (SAS/STAT, CATMOD pro cedure) of the proportion of prey killed (Ne) in relation to initial prey density (N0). The handling times and attack coefficients were estimated using Holling’s disk equation. Statistical analysis of the functional response was performed using the SAS software. Results In all the predator stages, according to the logistic regressions results, linear parameter, P1 was negative that shows a type II functional response. The response curve rises in a negatively accelerating manner to a plateau and the proportion of preys consumed by a predator decreases exponentially as the prey density increases. In highest densities, mean number of consumed aphids by third, fourth, and male and female adults were determined 50.5, 69.2, 75 and 83.9 aphids, respectively. Based on Rogers’s random equation, the lowest (0.0560 h-1) and the highest (0.1370 h-1) attack rates were obtained for third larval instar and adult female, respectively. Handling time was shortest (0.1821 h) in third larval instar and longest (0.2870 h) in female adult. Discussion Based on positive predatory characteristics including voracity and high searching efficiency of females, H. axyridis has high predation capacity and can be important in suppressing the T. kahawaluokalani populations.