Developmental response of tropi cal warehouse moth, Ephestia cautella (Walker) (Lepidoptera: Pyralidae)'s larvae to stored cocoa beans fermented at varied degrees

Abstract

Developing larvae of major insect pests like Ephestia cautella rapidly degrade stored cocoa beans through feeding and other biological activities on the beans. Completion of developmental stages of insects may be influenced by a number of biochemical factors triggered by the primary post-harvest processing of cocoa beans prior to storage. Hence, this study assessed the development of E. Cautella from first instar larval stage to adult stage on cocoa beans fermented at varied degrees. Fresh ripening pods of Amelonado variety (N38) were harvested and fermented variedly at 0 - 7 days, and sun-dried to about 5 - 6% moisture content. The variedly fermented cocoa beans (300g/treatment) were infested with newly hatched first instar larvae of E.cautella (N=10) in a completely randomized design with four replications at 28±2°C and 70±5% relative humidity(RH). Days to adult emergence of the larvae of E.cautella on the cocoa beans varied significantly (P>0.05) between 0 day and 76.50 days in 4 days and 7 days-fermented beans, respectively. Significant variations occurred (P>0.05) in the total adult emergents of E. cautella, ranging between 0 and 8.25 in 4 days and 1 day fermented beans, respectively. This study reveals that the fermentation period of cocoa beans prior to drying and storage influenced adult emergence of E.cautella on stored cocoa beans, with 0 - 3 days fermented beans highly susceptible to E.cautella’s development to adult stage. Cocoa beans need to be fermented adequately for 4 to 7 days before drying to prevent insects’ damage. Notably, 4-days fermented cocoa beans did not support E.cautella development to adult stage at 90 days post larvae-introduction. The 4-days fermented cocoa beans require further investigations for its nutritional suitability and importance in human diets.

Keywords: Varied fermentation, Ephestia cautella, total adult emergents, days to adult emergence