| Popis: |
To develop a rearing programme for the egg parasitoid Trichogrammatoidea lutea for augmentative biological control, the effects of ultraviolet (UV) irradiated host eggs were evaluated on the number of eggs parasitized, development time, number of progeny and sex ratio of T. lutea, using eggs of the lepidopteran species Helicoverpa armigera, Chilo partellus and Cadra cautella as hosts. UV-irradiation of 13 min was sufficient to kill embryos of all three hosts. The highest mean percentage parasitism on UV-irradiated and un-irradiated eggs occurred on those of H. armigera (47.8% and 33.3%) and C. cautella (33.2% and 55.5%), followed by C. partellus (6.6% for both). The mean number of individuals emerged per single parasitized host of UV-irradiated and un-irradiated eggs was highest for H. armigera (2.5 and 2.1) and lower for C. partellus (1.3 and 1.4) and C. cautella (0.9 and 0.8). The sex ratio of T. lutea was female-biased on UV-irradiated eggs of H. armigera, on UV-irradiated and un-irradiated eggs of C. cautella, and male-biased for C. partellus eggs and un-irradiated eggs of H. armigera. The developmental time of T. lutea from egg to adult male and female differed slightly between UV-irradiated and un-irradiated eggs. Overall, UV-irradiation of host eggs had negligible effects on percent parasitism, number of progeny per parasitized egg and sex ratio of T. lutea. Of the three lepidopteran species evaluated, H. armigera appears to be the most suitable host for mass-rearing of T. lutea. The results indicate that UV-irradiation of Lepidoptera eggs is suitable for mass rearing of T. lutea. |
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