Depth of pupation and survival of the Oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae) pupae at selected soil moistures

Estimates of pupation depth and survival of the Oriental fruit fly, Bactrocera dorsalis (Hendel), are important for optimizing soil control and for better understanding its natural mortality in the agricultural system of Guangzhou, China. Late third-instar larvae were placed in soils having relative moistures of 0–100% for pupation. No pupae were found on the surface at soil moistures of 0–70%. Instead, more than 50% of the larvae pupated on the surface at soil moistures of 80, 90, and 100%. Most of the larvae preferred to pupate in less than 4 cm of the soils, while relatively few larvae moved more than 4 cm when the soils received too little water or too much water. The survival rate of pupae at 70% moisture level was low, and the pupae were unable to survive at soil moistures of 0, 80, 90, and 100%, while emergence rates exceeded 90% at the conditions of 10–60% moisture levels. Moreover, soil moistures had an influence on the average time to emergence (average time between the larvae release and the emergence of adults). Adult flies at 30% moisture level emerged earlier than those at the other moisture levels, whereas the average time to emergence at 70% moisture level was the longest.