The diamondback moth, Plutella xylostella (L.), is one of the most economically damaging pests of cruciferous crops worldwide, and its widespread resistance to synthetic insecticides has intensified interest in plant-derived alternatives. In the present study, hexane and ethyl acetate extracts of six plant species viz., Azadirachta indica, Nerium oleander, Plumeria rubra, Sesbania grandiflora, Swietenia macrophylla and Tagetes erecta was obtained by Soxhlet extraction and evaluated at 5% concentration for their effects on larval weight gain, pupal weight and adult weight of P. xylostella under laboratory conditions, with azadirachtin 1% EC (2 ml/l) as a treated check and solvent and untreated checks for comparison. Both the extracts of six plant species significantly reduced larval, pupal and adult weights relative to the untreated and solvent checks (p < 0.001). Among the botanicals, S. grandiflora and S. macrophylla were consistently the most active comparable to the azadirachtin treated check, whereas their hexane and ethyl acetate extracts produced strong but sub-lethal growth suppression. Ethyl acetate extracts generally produced greater sub-lethal growth suppression than the corresponding hexane extracts for most species. These results indicate that solvent polarity strongly influences the growth- and development-inhibiting potency of these botanical extracts against P. xylostella, with ethyl acetate extracts of S. grandiflora and S. macrophylla emerging as the most promising candidates, approaching the potency of azadirachtin, for further evaluation as components of botanical-based integrated pest management programmes.