Effect of irrigation on population growth of pomegranate aphid, Aphis punicae (Hem.: Aphididae)

Pomegranate aphid, Aphis punicae (Passerini) (Hem.: Aphididae), damages pomegranate trees through feeding and producing considerable amounts of honeydew. The effect of drought stress on fertility-life table parameters of A. punicae was studied by using leaf cages on plant in three treatments including control (irrigation at 100% of field capacity), moderately (at 75% of field capacity) and highly (at 50% of field capacity) drought stressed pomegranate plants (Robab cultivar) in greenhouse (natural photoperiod, 30±5˚C and 50±10% RH). Life table parameters and their pseudo-replication were calculated by a computer program for the age-stage two sex life table analysis and bootstrap technique (10000 replications), respectively. The highest mean number of nymphs per female (16.54 nymphs), female adult longevity (7.14 days), the intrinsic rate of increase (0.39 day-1), the finite capacity for increase (1.74 day-1) and the net reproductive rate (15.19 nymphs) were observed in aphids that reared on moderately drought stressed trees. The highest mean generation time of A. punicae was 8.02 days in aphids reared at control condition. Amount of proline, phenol and soluble carbohydrate in leaves increased by increasing drought stress and the highest amount were measured in plant under highly drought stress. Considering that the highest population growth rate of pomegranate aphid calculated in plants under moderately drought stress, it seems that the highest quality of host plant for aphids obtained under this irrigation condition. Also, highly drought stress can lead to a decrease in aphid population growth by increasing the level of plant defensive compounds.