Life history parameters of the coccinellid beetle, Oenopia conglobata contaminata, an important predator of the common pistachio psylla, Agonoscena pistaciae (Hemiptera: Psylloidea)

The predatory beetle, Oenopia conglobata contaminata, is associated with the common pistachio psylla, Agonoscena pistaciae, the major pistachio pest in Iran. Successful development and reproduction on both A. pistaciae and Aphis gossypii (the major weed aphid in the pistachio orchards) indicated they were suitable prey for O. conglobata contaminata. Under ample prey supply, larval development on A. pistaciae was shorter and mortality was lower compared to those reared on A. gossypii. Furthermore, this ladybird attacks and destroys a large number of psyllid nymphs during the whole of its larval period (620±17 fourth stage nymphs) and also in its adult stage (191±7.5 4^th stage nymphs daily). The optimum temperature for development was 30°C, the theoretical threshold for development was 13°C and thermal requirements from egg to adult was estimated as 196 degree-days (°D). Fecundity for the first 21 days of adult life was 387 and 355 eggs when females fed on A. pistaciae and A. gossypii nymphs, respectively. The intrinsic rate of increase (r_m) at 27.5°C was 0.19 and 0.18 when ladybirds were fed on psyllid and aphid nymphs, respectively. In a laboratory choice experiment, the adult ladybirds showed a strong preference for A. pistaciae compared to A. gossypii. This was in agreement with our field observation that O. conglobata contaminata is almost always found on psyllid colonies, even when aphids were plentiful on weeds in the pistachio orchards. The influence of the predator on psyllid seasonal population under natural condition was not studied in this investigation and this subject must be measured in subsequent trials.