Day-degree development and phenology modelling of the immature stages of Chrysophtharta agricola (Chapuis) (Coleoptera: Chrysomelidae), a pest of eucalypt plantations

Day-degree developmental requirements and lower temperature thresholds were determined in the laboratory for the immature lifestages and preoviposition periods of Chrysophtharta agricola, a pest of eucalypt plantations in Tasmania and Victoria. These data were used to provide a predictive model for C. agricola's spring-summer phenology under field conditions. The model was validated using field data from two Tasmanian field sites over three seasons. Lower temperature thresholds for immature development ranged from 2.8°C (Liv) to 10.3°C (Li), while the lower temperature threshold for oviposition was 7.4°C for teneral and overwintered adults. Total immature development time (egg-adult) was approximately 400 ± 16 DD above 8 ± 0.41°C. Development time did not differ between males and females, or between offspring of different females. Beetles reared at 25°C were significantly larger than those reared at low temperatures. Day-degree models were usually a good predictor of the appearance of developmental stages in the field.