Biological control potential of an aphid parasitoid, Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) against Brevicoryne brassicae (Linnaeus) (Hemiptera: Aphididae), a pest of oilseed brassicas in India

Abstract

Biological and behavioural attributes of Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) were studied on Brevicoryne brassicae (Linnaeus) (Hemiptera: Aphididae). The total developmental duration of the parasitoid was longer in younger nymphal instars compared to that in older nymphal instars of aphid. Host age affected the oviposition period and fecundity of the ovipositing parasitoid. Survival of the immatures was higher in older as compared to the younger instars. Sex ratio for the parasitoid was found to be female-biased. Adult longevity of D. rapae was longer for females compared to that of males. Mean longevity of adult female parasitoid was longer, while parasitizing nymphs of younger age groups (1–2 days) compared to that of older age groups (4–5 days). B. brassicae reared on cabbage (Brassica oleracea var. capitata) was found to be the best host for D. rapae based on high per cent parasitism and high fecundity. The parasitoid showed a higher preference towards third nymphal instar of B. brassicae both in choice and no-choice tests. The results from experiments on mutual interference revealed that per capita searching efficiency decreased significantly from 0.99 to 0.05 with an increase in parasitoid densities from 1 to 8. Logistic regression exhibited a type II functional response for D. rapae. The handling time (Th) and searching efficiency (a) values were calculated to be 1.35 ± 0.05 h and 0.025865 ± 0.001525 h, respectively. This investigation suggests that D. rapae could be an effective biocontrol agent of B. brassicae that would supplement its management options in oilseed brassicas.