In this study, some behavioral characteristics of Diaeretiella rapae (McIntosh), parasitoid wasp of cabbage aphid (Brevicoryne brassicae L.) were studied. The main purpose was to evaluate the rate of efficacy of D. rapae by studying functional response, host stage preference as well as mutual interference parameters. All experiments were conducted in laboratory at 25+1°C, 60+5% RH and a photoperiodism of 16:8 h (L:D).
In functional response experiment, second instar nymphs of aphid in different densities were presented to individual parasitoid females for 24 hours. First to fourth instar nymphs as well as adult aphids were used for conducting host stage preference experiment. Different wasp densities were used in mutual interference study. The functional response of parasitoid to different densities of host was of type II. There was a significant relationship between wasp density and per capita searching efficiency. The interference index indicated that as the wasp density increased, per capita searching efficiency decreased. The results in host stage preference experiment indicated that D. rapae prefered second instar nymphs more. First instars and adults were less preferred than others for parasitising.
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