Bionomics of an Aphidiid Parasitoid<i>Trioxys indicus.</i>30. Effect of Host Plants on Reproductive and Developmental Factors

Abstract

ABSTRACT The present work was undertaken to evaluate the effect of three cucurbit host plants, viz., Lagenaria vulgaris, Luffa cylindrica and Cucurbita maxima on the oviposition pattern, fecundity, developmental rate, longevity and sex ratio of the parasitoid Trioxys indicus on its host Aphis gossypii. The daily oviposition pattern of T. indicus did not vary significantly in host insects bred on different host plants. However, the frequency of oviposition was significantly less in the hosts bred on C. maxima than others. The female laid about 80% of the total eggs during the first four days irrespective of the host plants. The females oviposited for 8.3 ± 0.95 days, 5.5 ± 1.08 days and 5.3 ± 0.67 days in the hosts reared on L. vulgaris, C. maxima and L. cylindrica respectively. The oviposition period also corresponded with the life-span. Host plants significantly influenced the mean fecundity of T. indicus. It was approximately three times as high on the aphids bred on L. vulgaris (164.5 ± 18.87 mummies/female) and L. cylindrica(144.0± 18.16mummies/female)than on C. maxima (51.3 ± 13.57 mummies/female). The rate of development of both sexes of T. indicus was not influenced by host plants at all. However, host plants significantly influenced the sex ratio of the parasitoid; C. maxima substantially reducing the production of females. The findings established a direct relationship between the host plants and the parasitoids and, therefore, the importance of the host plants as a factor in the success of a bioagent should also be considered.