Temperature-dependent development of Otiorhynchus ovatus (Coleoptera : Curculionidae) pupae

Temperature-dependent development of strawberry root weevil, Otiorhynchus o vatus (L.), pupae was studied in strawberry (Fragaria X ananassa Ouch. vari ety 'Totem'). The development of pupae was investigated at constant tempera tures from 3 to 33 degrees C at 3 degrees C intervals. The upper thermal le thal limit for strawberry root weevil pupae was between 30 and 33 degrees C . Pupae did not eclose below 6 degrees C. Pupal duration was 127 d at 6 deg rees C and 7 d at 30 degrees C. Rate of development (1/d) was greatest at 3 0 degrees C. We used the development of strawberry root weevil as a model s ystem to suggest a modification on the traditional method of creating linea r degree-day models. This method used weighted regression and was based on the assumption that the purpose of creating prediction models is to model t he development of insects based on the temperatures to which they are expos ed in the field. The predictive ability of this weighted model was compared with a traditional nonweighted linear degree-day model by relating predict ions to the observed occurrence of strawberry root weevil lifestages determ ined by field sampling. The weighted linear pupal prediction model produced a developmental threshold of 4.3 degrees C and a degree-day requirement of 227.3. The nonweighted linear pupal prediction model produced a developmen tal threshold of 6.2 degrees C and a degree-day requirement of 163.9. Using a weighting method maintains the utility of a linear model while allowing for more accurate estimate of the lower developmental threshold.