Abstract
The impact of host plant-aphid combination on the prey consumption and prey preference by adult ladybird, Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae) was studied, using aphid-prey, Aphis craccivora (Koch) and Lipaphis erysimi (Kalt.), in the laboratory. Monotypic aphids, A. craccivora, raised separately on Indian bean, Dolichos lablab L., and poison buttercup, Ranunculus sceleratus L., and L. erysimi cultured on radish, Raphanus sativus L., and mustard, Brassica campestris L., were provided. Adult male and female ladybirds consumed significantly greater number of A. craccivora infested on D. lablab than those on R. sceleratus. Similarly, they consumed a greater number of L. erysimi raised on R. sativus than those on B. campestris. The results indicated that host plant allelochemicals/toxicants had a direct effect on the palatability and prey consumption, as the ladybird treated the same aphids differently that was raised on different hosts. Prey preference, using a choice condition, was tested by providing both the aphid species raised on toxic hosts in a common microcosm. Both adult male and female of M. sexmaculatus preferably consumed the aphid, A. craccivora-infested R. sceleratus over L. erysimi-infested B. campestris in all diet treatments. The preference indices (β and C) further skewed the results towards A. craccivora, which suggest that ladybirds preferred A. craccivora on encountering aphids raised on toxic hosts. It could be concluded that dietary selection in ladybirds depends largely on the aphid–host combination, and a suitable host may aid the augmentative rearing of both aphids and ladybirds.
Highlights
Majority of ladybirds (Coleoptera: Coccinellidae) are important predators and biocontrol agents of numerous phytophagous pests, viz. aphids, scale insects, mealy bugs, thrips, mites, and whiteflies (Omkar and Pervez 2004, 2016; Hodek et al 2012)
The proportions of the two aphids consumed by the adults M. sexmaculatus were subjected to two-way ANOVA using “aphid species” and “gender” as independent variables and “proportion of prey consumed” as a dependent variable (SAS 9.0, 2002). Both adult male (F = 25.86; P < 0.0001; df = 3, 39) and female (F = 45.51; P < 0.0001; df = 3, 39) of M. sexmaculatus consumed significantly greater number of aphids, A. craccivora infested on D. lablab, followed by L. erysimi infested on R. sativus (Fig. 1)
This revealed that A. craccivora cultured on D. lablab was the best aphid–host combination culminating in maximum prey consumption
Summary
Majority of ladybirds (Coleoptera: Coccinellidae) are important predators and biocontrol agents of numerous phytophagous pests, viz. aphids, scale insects, mealy bugs, thrips, mites, and whiteflies (Omkar and Pervez 2004, 2016; Hodek et al 2012). Aphids, scale insects, mealy bugs, thrips, mites, and whiteflies (Omkar and Pervez 2004, 2016; Hodek et al 2012). A thorough understanding of ladybirds’ dietary habits can help in maximizing their biocontrol potential (Michaud 2005; Provost et al 2006; Sloggett 2008a, b; Hodek and Evans 2012; Pervez et al 2018). Diet suitability in aphidophagous ladybirds seems unpredictable, as the same aphid can be both toxic and nutritious (Guroo et al 2017). Earlier reports considered black bean aphid, Aphis craccivora (Koch), as unsuitable food for ladybirds (Hodek 1996), due to the presence of toxic allelochemicals, viz. (=Lablab purpureus L.), and recommended it as the most suitable prey for mass rearing of certain aphidophagous ladybirds (Omkar and Mishra 2005; Chaudhary et al 2016) Recent findings suggested it to be highly nutritious after being raised on Indian bean, Dolichos lablab L. (=Lablab purpureus L.), and recommended it as the most suitable prey for mass rearing of certain aphidophagous ladybirds (Omkar and Mishra 2005; Chaudhary et al 2016)
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