oa Journal of the Entomological Society of Southern Africa - Sex ratios in adult populations of codling moth (Lepidoptera: Olethreutidae)
Sex ratios in orchard populations of adult codling moths, Laspeyresia pomonella (L.), were determined by sexing 16 412 pupal cases of newly emerged adult codling moths, collected at regular intervals for 10 consecutive years from marked zones on 120 unsprayed trees in a two-hectare pear orchard. There was a significant seasonal pattern in the adult sex ratios of the tri-voltine indigenous strain and highly significant differential ratios within each respective phase of the basic pattern. The overall adult female to male ratio was 0,9: I ,0. During the pre-blossom phase the ratio was 0,8: 1,0 and in the post-blossom phase of the first brood 1,3: I ,0. The overall first brood ratio was I, I: 1,0 showing that a preponderance of females emerged after the winter larval diapause. The ratios were 0,9: I ,0 and 0,7: 1,0 in favour of males in the second and third broods, respectively. The possible bearing of the seasonal pattern of differential sex ratios on interpretation of data from sex trap monitoring systems is discussed.
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