New associations and host status: infestability of kiwifruit by the fruit fly species Bactrocera dorsalis, Zeugodacus cucurbitae, and Ceratitis capitata (Diptera: Tephritidae).
We conducted no-choice cage and field infestation studies to determine if the fruit of kiwifruit (Actinidia chinensis var. deliciosa, 'Hayward' [green-fleshed], and Actinidia chinensis var. chinensis, 'Zesy002' [gold-fleshed]) are hosts for three invasive tephritid fruit fly species that may enter New Zealand or other kiwifruit growing areas. For cage studies, punctured and unpunctured (intact) fruits of green and gold kiwifruit were exposed to gravid female flies of Bactrocera dorsalis (Hendel) (Oriental fruit fly), Zeugodacus cucurbitae (Coquillet) (melon fly), or Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), in screen cages outdoors for 24 h, and then held on sand in the laboratory for three weeks for pupal development and adult emergence. Unpunctured green kiwifruit produced an average of 1.3, 0.0 and 48.8 puparia per kg of fruit for B. dorsalis, Z. cucurbitae and C. capitata, respectively. Unpunctured gold kiwifruit produced an average of 54.7, 6.1 and 0.0 puparia per kg of fruit for B. dorsalis, Z. cucurbitae and C. capitata, respectively. For comparison, unpunctured papaya, a preferred host for all three species, produced 492-795 puparia per kg of fruit across all species. These results indicate that kiwifruit is a poor ovipositional host for B. dorsalis, Z. cucurbitae and C. capitata. When kiwifruit were punctured to facilitate oviposition, the number of puparia per kg fruit increased significantly compared with those on unpunctured fruit for B. dorsalis, but not for Z. cucurbitae or C. capitata, indicating that kiwifruit is a poor developmental host for these two species. For all fruit fly species, the average weight of individual puparia recovered from green and gold kiwifruit was roughly 50% of the weight of puparia recovered from papaya. Field infestation of kiwifruit suspended from papaya trees resulted in no infestation of green kiwifruit and very low infestation of gold kiwifruit by B. dorsalis, and no infestation in either cultivar by Z. cucurbitae under natural conditions. Overall, kiwifruit is a poor host for B. dorsalis, Z. cucurbitae and C. capitata. This information will help inform decisions about quarantine restrictions and potential crop loss in the event of incursions of these fruit flies into New Zealand or other kiwifruit producing countries.