Cold-hardiness and development of eggs of Rhopalosiphum insertum |
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Authors: | B. D. JAMES M. L. LUFF |
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Affiliation: | Department of Agricultural Biology, University of Newcastle upon Tyne |
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Abstract: | Abstract. 1. The eggs of Rhopalosiphum insertum (Walker) showed a seasonal increase in cold-hardiness under field conditions. Their supercooling point fell from -35°C in November to below -40°C in January, then rose to-35°C or above by March. 2. Laboratory experiments demonstrated that both temperature and date affected cold-hardiness of the eggs. The supercooling points of eggs kept at 16 h photoperiod or in darkness did not, however, differ significantly. 3. Eggs brought from the field into warm, long-day conditions would not hatch until after mid-January. After this date, per cent hatch was significantly greater in 16 h photoperiod than in darkness; it did not differ between eggs kept at 5 or 0°C, but was reduced at -5°C. 4. It is concluded that eggs of Rinserturn are in diapause until mid-January, and that hatching rate and cold-hardiness are determined by separate environmental factors. |
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Keywords: | Aphids supercooling cold-hardiness diapause apple Rhopalosiphum. |
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