Author
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McQuate, Grant |
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Vargas, Roger |
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Submitted to: Fruit Flies of Economic Importance International Symposium
Publication Type: Abstract Only Publication Acceptance Date: 7/31/2006 Publication Date: 9/13/2006 Citation: Mcquate, G.T., Vargas, R.I. 2006. Effectiveness of bait sprays on border windbreaks for population suppression of Bactrocera spp. in papaya orchards. Fruit Flies of Economic Importance International Symposium. Interpretive Summary: Effectiveness of bait sprays for suppression of tephritid fruit fly populations requires that they be applied in areas where the flies feed. It is standard practice to apply bait sprays to plants bordering a host crop area, and not to the host crop itself, for suppression of melon fly, Bactrocera cucurbitae (Coquillett), populations. In contrast, bait spray applications for suppression of oriental fruit fly, B. dorsalis (Hendel), populations have traditionally been applied to the host crop, rather than to crop borders. However, in certain crop environments (e.g., papaya, Carica papaya), oriental fruit flies roost on some non-host plants adjacent to the crop. To better understand the importance of roosting hosts for both melon fly and oriental fruit fly, we (1) Tested the attractiveness of a range of plant species as roosting hosts; (2) Compared roosting behavior of the two fruit fly species in one roosting host; and (3) Tested the efficacy of bait sprays applied to a wiliwili (Erythrina variegata) hedgerow bordering a papaya orchard for suppression of populations of both fly species. (1) Roosting Hosts. Relative attractiveness of potential roosting hosts was tested using protein-baited traps associated with clusters of potted plants placed 20 m distant from a fruiting papaya orchard known to have established populations of both oriental fruit fly and melon fly. We identified castor bean (Ricinus communis), panax (Polyscias guilfoylei), wiliwili, and guava (Psidium guajava) as preferred roosting hosts for melon fly and wiliwili, panax, castor bean, cocklebur (Xanthium strumarium), christmasberry (Schinus terebinthifolius), ti leaf (Cordyline terminalis), guava and several Citrus spp. as preferred roosting hosts for oriental fruit fly. Establishment of preferred roosting hosts as crop borders provides sites for bait spray applications for suppression of both fruit fly species. (2) Roosting Host Utilization. Using torula yeast – baited traps hung at different heights in the columnar form of wiliwili trees bordering papaya orchards, we found that oriental fruit flies roost, on average, at a higher height. This difference in roosting height may relate to the difference in height of common host fruits of the two fly species. The higher roosting height could make it more difficult to control oriental fruit fly populations if bait sprays cannot be readily applied to the higher parts of the roosting host. (3) Suppression Test in Papaya Orchard Setting. We made weekly applications of the spinosad-based GF-120NF Fruit Fly Bait to wiliwili borders of papaya orchards in Kapoho, Hawaii, which had good populations of both melon fly and oriental fruit fly. Fly populations were assessed through weekly catches at torula yeast - baited traps positioned in the wiliwili borders, as well as in the orchard, and through infestation rates of ground fruits collected weekly. Overall, both melon fly and oriental fruit fly populations were suppressed by bait sprays applied only to the bordering vegetation, but additional suppression techniques (e.g., male annihilation) would be needed to further reduce the fruit infestation rate. We discuss the difference in effectiveness between the two fruit fly species and note that additional research is needed to better understand the relative use of host crops versus border plants for roosting of oriental fruit flies in different crop environments. Technical Abstract: It is standard practice to apply bait sprays to plants bordering a host crop area, and not to the host crop itself, for suppression of melon fly, Bactrocera cucurbitae (Coquillett), populations. In contrast, bait spray applications for suppression of oriental fruit fly, B. dorsalis (Hendel), populations have traditionally been applied to the host crop, rather than to crop borders. However, in certain crop environments (e.g., papaya, Carica papaya), oriental fruit flies roost on some non-host plants adjacent to the crop. To better understand the importance of roosting hosts for both melon fly and oriental fruit fly, we (1) Tested the attractiveness of a range of plant species as roosting hosts; (2) Compared roosting behavior of the two fruit fly species in one roosting host; and (3) Tested the efficacy of bait sprays applied to a wiliwili (Erythrina variegata) hedgerow bordering a papaya orchard for suppression of populations of both fly species. (1) Roosting Hosts. Relative attractiveness of potential roosting hosts was tested using protein-baited traps associated with clusters of potted plants placed 20 m distant from a fruiting papaya orchard known to have established populations of both oriental fruit fly and melon fly. We identified castor bean (Ricinus communis), panax (Polyscias guilfoylei), wiliwili, and guava (Psidium guajava) as preferred roosting hosts for melon fly and wiliwili, panax, castor bean, cocklebur (Xanthium strumarium), christmasberry (Schinus terebinthifolius), ti leaf (Cordyline terminalis), guava and several Citrus spp. as preferred roosting hosts for oriental fruit fly. Establishment of preferred roosting hosts as crop borders provides sites for bait spray applications for suppression of both fruit fly species. (2) Roosting Host Utilization. Using torula yeast – baited traps hung at different heights in the columnar form of wiliwili trees bordering papaya orchards, we found that oriental fruit flies roost, on average, at a higher height. This difference in roosting height may relate to the difference in height of common host fruits of the two fly species. The higher roosting height could make it more difficult to control oriental fruit fly populations if bait sprays cannot be readily applied to the higher parts of the roosting host. (3) Suppression Test in Papaya Orchard Setting. We made weekly applications of the spinosad-based GF-120NF Fruit Fly Bait to wiliwili borders of papaya orchards in Kapoho, Hawaii, which had good populations of both melon fly and oriental fruit fly. Fly populations were assessed through weekly catches at torula yeast - baited traps positioned in the wiliwili borders, as well as in the orchard, and through infestation rates of ground fruits collected weekly. Overall, both melon fly and oriental fruit fly populations were suppressed by bait sprays applied only to the bordering vegetation, but additional suppression techniques (e.g., male annihilation) are needed to further reduce the fruit infestation rate. We discuss the difference in effectiveness between the two fruit fly species and note that additional research is needed to better understand the relative use of host crops versus border plants for roosting of oriental fruit flies in different crop environments. |
