The relationship between adult preference and offspring performance in the invasive tephritid species, Dacus frontalis, of wild and cultivated cucurbitaceous hosts at different stages of fruit maturity.

Abstract

Dacus frontalis (Diptera:Tephritidae), is an emerging pest that causes damage to fruit in Africa and now represent a threat to Cucurbitaceae production in Europe. Understanding interactions between D. frontalis and host plants is important to improve pest management and prevent their invasions in areas where this pest is not yet established. In this study, female preference and larval performance of D. frontalis with regard to wild and cultivated Cucurbitaceae species at different stages of fruit maturity (green, intermediate, and ripe) were examined. Host plant quality, species, and fruit maturity play a major role in oviposition preference under both choice and no-choice conditions. They also influence larval performance (larval survival, development time, and pupal weight). Larval survival rates differed significantly between fruit species and different stage of fruit maturity, ranging from 0.2% to 0.7% in the case of ripe melon and green Bitter apple, respectively. Larval performance was higher in fruit with low soluble sugar, such as green bitter apple. Results revealed that D. frontalis has distinct ovipositional preferences for the cucurbitaceous host plants tested, with a clear preference for cultivated fruit compared with wild fruit. In cultivated cucurbitaceous fruit, the highest number of eggs was laid on the oviposition device containing green cucumber (48 eggs/female) and the lowest on that containing green melon fruit, where there was no oviposition. Females of D. frontalis were able to choose fruit for oviposition that promoted high larval performance, such as cucumber, pumpkin, zucchini, and watermelon particularly at the green stage. This behaviour reveals a positive preference-performance relationship. Predicting the interactions between exotic insects and their potential host plants is important for preventing invasions using Pest Risk Analyses and associated quarantine procedures.