Effects of winter temperatures on the sex ratios ofAphytis melinus [Hym.: Aphelinidae] in the San Joaquin Valley of California |
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Authors: | R. W. Hoffmann C. E. Kennett |
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Affiliation: | (1) Division of Biological Control, University of California, 94720 Berkeley |
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Abstract: | Laboratory bioassays of overwintering field populations of the California red scale parasitoidAphytis melinus DeBach showed a shift in sex ratio of F1 progeny after prolonged exposure to winter temperatures in Tulare County, California. In 7 of 8 tests, short-term winter field exposure (<75 days) did not result in a significant male bias in sex ratios of F1 progeny when compared to sex ratios observed in laboratory cultures maintained at 27°C. Long term exposure (109–139 days), however, resulted in significantly (P<0.05) higher male bias in F1 sex ratios in 5 of 6 tests. These results from field populations ofA. melinus agree with conclusions of low temperature laboratory tests onAphytis species (lingnanensis, melinus) by other workers. Mention of a proprietary or commercial product in this paper does not constitute an endorsement of this product by the University of California. |
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Keywords: | Biological control Aphytis melinus low temperature sex-ratio |
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