C. O estudo foi realizado em câmaras climáticas, com umidade de 80-90% e fotoperíodo de 8L:16D. Após a eclosão, as larvas foram alimentadas com folhas tenras de cedro (Cedrela odorata) e inspecionados a cada 24h para determinar a duração das fases larval e de pupa, e a emergência dos adultos em cada temperatura. As relações entre essas variáveis e a temperatura foram analisadas através de ANOVA, regressão e correlação. A temperatura teve grande influência no desenvolvimento das fases imaturas e na emergência dos adultos de H. grandella. A duração do ciclo biológico (ovo-adulto) variou de 30 dias (30ºC) a 104 dias (15ºC). A mortalidade do estágio larval foi alta nessas temperaturas, alcançando taxas de 90% (15°C) e 45% (30ºC). A mortalidade de larvas de primeiro instar foi também relativamente alta (51-75%) nas temperaturas dentro do intervalo de 15ºC a 30ºC, com exceção daquelas que se desenvolveram a 25ºC (14%). O peso das pupas foi menor em temperaturas extremas (15ºC e 30ºC). A estimativa da temperatura base de desenvolvimento para todos os estágios imaturos (8,5ºC) permitiu calcular a constante térmica (1320 graus dias), a qual possibilitará a previsão de picos populacionais no campo. PALAVRAS-CHAVE: Meliaceae, taxa de desenvolvimento, limiar térmico, constante térmica, Costa Rica ABSTRACT -Developmental response of the mahogany shootborer, Hypsipyla grandella (Zeller), to temperature was determined in laboratory trials in Turrialba, Costa Rica. Two hundred fresh eggs (less than 24h old) were placed individually inside glass flasks, and exposed to seven constant temperatures (10, 12.5, 15, 20, 25, 30 and 35°C), in separate experiments. These were carried out in environmental chambers, at 80-90% relative humidity and 8L:16D photoperiod. After hatch, larvae were fed tender foliage of Spanish cedar (Cedrela odorata) and were inspected every 24h to determine larval and pupal duration, and adult emergence, at each temperature. Relationships between these variables and temperature were analyzed by means of ANOVA, regression and correlation procedures. Temperature greatly influenced development of H. grandella immature stages and adult emergence; development time varied between 30 days (30ºC) and 104 days (15°C). Larval mortality was high at those temperatures, reaching values of 90% (15°C) and 45% (30ºC). Also, mortality of the first larval instar was relatively high (51-75%) at all temperatures in the range 15-30°C, except at 25ºC (14%). Pupal weight was lower at extreme temperatures (15ºC and 30ºC). Estimation of a common lower thermal threshold for all immature stages (8.5ºC) allowed calculation of a general thermal constant (1320 degree-days), which could be used to predict population peaks in the field.
1 Population trends of Hypsipyla grandella and their relationship with abiotic (humidity, precipitation and temperature) and biotic factors (availability of mahogany shoots and natural mortality agents), as well as damage patterns, were studied for 16 months in Turrialba, Costa Rica. 2 Hypsipyla grandella was active in the field all year round, and its population density was influenced by temperature, availability of new shoots and natural mortality agents. 3 It was possible to predict four population peaks, which appeared approximately every 1881 degree-days. 4 Even though H. grandella larvae mainly attack shoots, they also fed on the bark of the bole, especially when green shoots were scarce. 5 Four parasitoid species were recorded (Bracon c. chontalensis, Brachymeria c. conica, Apanteles sp. and Dolichogenidea sp.) but their impact on H. grandella abundance was negligible.
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