Prey stage preference and functional response of the coccinellid Hyperaspis polita, feeding on the mealybug Nipaecoccus viridis

The spherical mealybug, Nipaecoccus viridis (Newstead) is one of the major citrus pests with economic importance in the world which also occurs in southern Iran, including Khuzestan province. In this research, prey stage preference and functional response of the coccinellid Hyperaspis polita Weise feeding on N. viridis were studied at 30 ± 1°C, 65 ± 5% RH and a photoperiod of 14:10 (L:D) h. Results indicated that the eggs of mealybug were preferred more than any other stages by most stages of H. polita, whereas adult females were less preferred. Results of logistic regression for 4th larval stage, adult female and adult male of ladybeetles by feeding on mealybug eggs, the preferred stage, revealed functional response type II, II and III, respectively. The searching efficiency (a) for 4th instar larvae and adult females were 0.2553 and 0.1983 h-1, respectively, using Rogers equations. Constant coefficient (b) for adult males was estimated to be 0.00405. The minimum handling time (Th) was estimated to be 0.0881 for 4th instar larvae and maximum was 0.3101 for adult males of ladybeetles. The maximum theoretical predation rate (T/Th) was calculated as 298.51 eggs/day by 4th instar larvae and minimum was 77.39 eggs/day by adult males. According to our results, it seems that H. polita has the potential for biological control of N. viridis. Nevertheless, additional field investigations of H. polita and comparison to other available predators would be necessary.