ABSTRACT
Avocados are generally poor hosts or nonhosts for tephritid fruit flies, which can influence the type of mitigation measures required by export protocols for trade. We conducted experiments to determine the susceptibility of the avocado, Persea americana, cv. 'Malama' to infestation by Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), in Hawai'i using laboratory and field no-choice cage tests, together with field sampling. In no-choice cage tests, infestation rates increased with decreasing fruit firmness over time after harvest. Although risk of infestation was negatively correlated with fruit firmness, about 50% of mature hard fruit exposed immediately after harvest became infested. In field cage tests, mature hard fruit on the tree at the 25% purple color stage were not infested, whereas fruit at the 50, 75, and 100% purple color stages were infested at relatively low rates. Field sampling of fallen 'Malama' fruit over two seasons showed no natural infestation by B. dorsalis and trap captures in avocado orchards using McPhail traps containing protein bait lures averaged 0.13 ± 0.03 (mean ± SE) flies per trap per week, underscoring the low prevalence of fruit flies in avocado orchards and the poor host quality of this cultivar. A systems approach based on poor host status, low prevalence, and a limited harvest period (October to March) and distribution area (northern tier states) is proposed to export 'Malama' avocados from Hawai'i to the continental United States.
Subject(s)
Persea , Tephritidae , Animals , Hawaii , Fruit , Drosophila , Systems Analysis , Insect Control/methodsABSTRACT
We examined the host status of the Australian finger lime, Citrus australiasica F. Muell. (Rutaceae), to Hawai'i's tephritid fruit fly pests using laboratory and field studies. In high-density (500 flies, 1:1 males and females) no-choice cage exposures (25 × 25 × 25-cm cage size), both undamaged and punctured finger limes were infested by Ceratitis capitata and Zeugodacuscucurbitae at a low rate compared to papaya controls, whereas Bactrocera dorsalis did not infest undamaged fruit, suggesting finger lime is a nonhost. In low-density (50 females) no-choice cage exposures, C. capitata and Z. cucurbitae readily oviposited in undamaged fruit but individuals rarely developed to the pupal or adult stage. For C. capitata, 274 finger limes exposed to 2000 gravid females, which laid an estimated 14,384 eggs, produced two pupae and no adults. For Z. cucurbitae, 299 fruit exposed to 2000 gravid females, which laid an estimated 4484 eggs, produced four pupae and one adult. Field sampling of undamaged fruit from the tree and off the ground from commercial farms produced five C. capitata pupa and one adult from 1119 fruit, for an infestation rate of 0.05 flies per kilogram of fruit; field collections found no natural Z. cucurbitae or B. dorsalis infestation, but the number of fruit available was too low to demonstrate nonhost status with a high degree of confidence.
