Influence of Different Diets on Two-sex Life Table Parameters of Oenopia conglobata contaminata (Menteries)

The common pistachio psylla (CPP), Agonoscena pistaciae Burckhardt and Lauterer, 1989 (Hem.: Psylloidea: Rhinocolinae) is an important pest of pistachio trees. The presence of a large population of psyllid causes severe problems such as falling buds and leaves and therefore this pest causes heavy economic damage to farmers. Predators are the largest and the most diverse natural enemies of the CPP. They are offered as biological control agents against pistachio pests, especially CPP, although they are mostly general predators. Oenopia conglobata contaminata (Menteries) is one of the common psylla predators of pistachio orchard that have a significant role in biological control of Agonoscena pistaciae population. Despite the importance of this efficient predator, the limited study has been done on the effect of different hosts on the biological parameters of this lady beetle. In this study, the demographic parameters of this lady beetle by feeding on 4 different prey species, A. pistaciae , Aphis fabae Scopoli (Hem.:Aphididae), Aphis gossypii Glover (Hem.:Aphididae) and eggs of Ephestia kuehniella (Zell.)(Lep.:Pyralidae) were studied in the laboratory conditions (25 ± 2°C, relative humidity of %65 ±5 and photoperiod of 16 hours light and 8 hours of darkness).
Nymphs of CPP (A.pistaciae) and adults of O. conglobata contaminata beetles were collected on the pistachio leaves from a pistachio orchard. Aphids (A. fabae and A. gossypii) were reared on the bean and the cotton plants planted in a greenhouse. Eggs of E. kuehniella were prepared from insectarium of Kerman Plant protection management and rearing of E. kuehniella was done in the laboratory conditions in Kerman Agricultural and Natural Resoarce Research Center. Before starting the experiment, one generation of O. conglobata contaminata was reared in the laboratory on the different host separately. One hundred eggs of O. conglobata contaminata were used to determine the demographic parameters. After hatching of eggs, larvae was individually transferred to a plastic container (5*10 cm) and kept in a growth chamber. Every day the larvae were fed with the above mentioned host. Their growth and development were monitored daily and also mortality rate was recorded. In the experiments, fourth-instar nymph of the aphids and A. pistaciae were used. The raw data of the developmental time and female daily fecundity of O. conglobata contaminata individuals were analyzed based on the age-stage, two-sex life table using the computer program TWO SEX MS Chart.
Results showed that the maximum net reproduction rate (R0) and intrinsic rate of increase (rm) in psylla diet was 290.87 , 0.1559, respectively and the minimum of R0 and rm belong to eggs of E. kuehniella diet (61.68 and 0.1103). This result proves that psylla diet is the best food for O. conglobata contaminata and aphids diets were in the next ranks (R0 and rm in A.fabae and A.gossypii diets were 200.48, 0.140; 72.44,0.128, respectively). Results of mean generation time of O. conglobata contaminata that was rearing on different diets showed that there were significant differences among the different diets. Mean generation time of O. conglobata in Psylla, A.fabae, A.gossypii and egg of E. kuehniella diets were 36.31, 37.72, 33.34 and 37.30 days, respectively. Finite rate of increase (λ) of O. conglobata contaminata by feeding A.pistasciae, A.fabae, A.gossypii and E. kuehniella was determined 1.198, 1.150, 1.136 and 1.116, respectively.The results of this study can be compared with the result of Mokhtari and Samih (2014), Rounagh and Samih (2014) and Hassani et al. (2009). Life expectancy of female and male O. conglobata contaminata by feeding A.pistasciae, A.fabae, A.gossypii and E. kuehniella were 80.82,64.16; 81.02,68.76; 80.54,68.88 and 59.75, 62.11 days, respectively. Results also indicated that the psylla and A.fabae diets improved the demographics parameters and the life expectancy of O. conglobata contaminata.
The results illustrated that this predator by feeding on nymphs of A. pistaciae has the highest intrinsic rate of increase (rm) and with respect to the demographic parameters, it was the most suitable prey .The compare of O. conglobata contaminata -rm that rearing by CPP with A. pistaciae -rm proves that this predator can control of A. pistaciae in the field and this ladybeetle can be used in IPM of pistachio orchards. According to the difficulty of rearing CPP in laboratory conditions, aphids are suitable preys for mass rearing of O. conglobata contaminata in insectariums.