Biological and behavioural characteristics of Diaeretiella rapae (McIntosh), a parasitoidof Lipaphis erysimi (Kaltenbach) infesting oilseed brassicas in India

摘要

Biological and behavioural characteristics of Diaeretiella rapae were studied in a laboratory using Lipaphis erysimi as a host. The total developmental period of the parasitoid was longer in early instars as compared to that in later instars. Host age at the time of oviposition affected the oviposition period, post-oviposition period and fecundity of the parasitoid. Survival of the immatures was higher in older than the younger instars. The sex ratio for the parasitoid was found to be female-biased. Adult longevity of D. rapae was longer for females when compared to that of males. The mean longevity of adult females of the parasitoid was longer while parasitizing nymphs of younger age groups (1-2 days) compared to that of older age groups (4-5 days). L. erysimi reared on mustard was found to be the best host for D. rapae based on high parasitisation (%), female-biased sex ratio and the shortest time required by the parasitoid for completion of the total developmental period. The parasitoid showed a higher preference towards second instar nymphs of L. erysimi, both in choice and no-choice tests. The per capita parasitisation and search efficiency of the parasitoid decreased with an increase in parasitoid density. Logistic regression exhibited type-II functional response for the parasitoid D. rapae. Overall, D. rapae appeared to be a potential biocontrol agent of L. erysimi that would supplement its biological control in oilseed brassicas.