Temperature Requirements for Development and Oviposition of the Carrot Weevil12

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Abstract
Laboratory studies were conducted to determine temperature thresholds and thermal requirements for development and reproduction of the carrot weevil, Listronotus oregonensis (LeConte), using a 16:8 L:D photoperiod and temperatures ranging from 7.2 to 32.3°C. Development rate, increased linearly with increasing temperature. Calculated thresholds and centigrade degree days (CDD) necessary for development were: egg, 9.5°C and 90 CDD; larvae, 6.7°C and 264 CDD; prepupae, 7.8°C and 107 CDD; pupae 7.2°C and 128 CDD; and total development from egg to adult, 7.0°C and 623 CDD. No oviposition occurred at 12.7°C with a threshold of 14.8°C and 131 CDD necessary for newly emerged carrot weevils to oviposit. The number of eggs laid per day increased as temperature increased, from 18.3 to 29.4°C, but at 32.3°C the number of eggs laid was reduced and the preoviposition period increased, indicating that the latter temperature was unfavorable for oviposition. Validation of laboratory data indicated a satisfactory fit between expected and observed development under field conditions.