Plant cultivars that negatively influence fitness of target phytophagous insects can be an important component of integrated pest management when they substantially restrict population growth of the target pest. In this study, the effects of seven cabbage (Brassica oleracea var. capitata L.) cultivars on survival and development of immature stages, pupal weights, moth longevity and oviposition rates of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), were evaluated in the laboratory. Under the no choice test, overall survival of P. xylostella immature stages was highest on Karabo (67.26 %) and lowest on Megaton (44.92 %). The larval and pupal developmental period, and thus generation time took longer on Empowa (18.48 d), Karabo (14.64 d) and Beverly Hills (17.48 d), while development on Hollywood F1 (13.79 d) was the fastest. Male and female P. xylostella pupal weights were lower in larvae that fed on Megaton (4.13 and 4.65 mg), Menzania (4.53 and 4.91 mg), and Hollywood F1 (4.11 and 5.08 mg), whereas pupal weights from Karabo (6.0 and 6.82 mg) were the heaviest. Unfed female moths reared on Beverly Hills lived the longest (5.05 d), whereas those reared on Leano (3.54 d) and Megaton (3.89 d) lived for a shortest period. Under the choice-test, P. xylostella laid significantly more eggs on Empowa (48.8 %) and Hollywood F1 (45.6 %) and least on Menzania (11.8 %) and Leano (10.6 %). Although these results show differential impact of the cultivars on the fitness parameters studied, low survival rate of offspring on a crop is the primary target for using plant resistance as a pest management tactic. As survival rates of immature P. xylostella were lower on Megaton together with lower pupal weights and moth longevity, which together negatively impacts fecundity, and thus overall fitness of the pest was lower when developing on it. Megaton was more resistant to P. xylostella. The results of this study show that Megaton can play a major role in restricting population growth of this pest and generational number of eggs deposited on it.
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Vol. 24 • No. 1