Functional Response of Cryptolaemus montrouzieri Mulsant (Col.; Coccinellidae) to Citrus Mealybug, Planococcus citri (Risso) (Hom.; Pseudococcidae) Under Laboratory Conditions

Appropriate functional response to prey or host densities is one of the important criteria for evaluating the efficacy of natural enemies in biological control programs. Cryptolaemus montrouzieri Mulsant is one of the main predators of citrus mealybug,Planococcus citri (Risso). In this research, the functional response of fourth larval instars and the female adults of this ladybird to different densities of second and third instars and female adults of citrus mealybug was studied under laboratory conditions. All experiments were carried out inside incubator with 25±1˚C, 80±5 %RH and photoperiod of 14 L:10 D hours. Individual fourth larval instars and female adults of ladybird were kept separately at densities of 4, 6, 8, 16, 20, 30, 40, 50 and 60 preys for 24 hours. Duration of each experiment was 24 hours and all experiments were carried out in 6 replications. A logistic regression was used to determine the type of functional responses and a nonlinear regression was used to fit Rogers and Holling’s equations to data for estimating searching efficiency (a) and handling time (Th) parameters. The results showed that the functional responses of fourth larval instars to different densities of second and third instars and the female adults of citrus mealybug were type III, III and II respectively, while the functional responses of the female adult ladybird to different densities of second and third instars and the female adults of prey were type II, III and II respectively. The rates of searching efficiency (a) for fourth larval instars of ladybird on second and third instars and the female adults of prey were estimated 0.0126, 0.0165 and 0.002, and the rates of handling time (Th) were obtained 0.701, 1.012 and 2.05, respectively. The rates of searching efficiency of female ladybirds on second and third instars and the female adults of prey were estimated 0.048, 0.013 and 0.098 and the rates of handling time were obtained 0.177, 0.843 and 2.79, respectively.