Development of Hypsipyla grandella (Zeller) (Lepidoptera: Pyralidae) in response to constant temperatures

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 35degreesC), 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 (30degreesC) and 104 days (15degreesC). Larval mortality was high at those temperatures, reaching values of 90% (15degreesC) and 45% (30degreesC). Also, mortality of the first larval instar was relatively high (51-75%) at all temperatures in the range 15-30degreesC, except at 25degreesC (14%). Pupal weight was lower at extreme temperatures (15degreesC and 30degreesC). Estimation of a common lower thermal threshold for all immature stages (8.5degreesC) allowed calculation of a general thermal constant (1320 degree-days), which could be used to predict population peaks in the field.