Assessment of Attractiveness of Plants as Roosting Sites for the Melon Fly, Bactrocera Cucurbitae, and Oriental Fruit Fly, Bactrocera Dorsalis

Authors: MCQUATE, GRANT; VARGAS, ROGER

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2007
Publication Date: 11/14/2007
Citation: Mcquate, G.T., Vargas, R.I. 2007. Assessment of Attractiveness of Plants as Roosting Sites for the Melon Fly, Bactrocera Cucurbitae, and Oriental Fruit Fly, Bactrocera Dorsalis. Journal of Insect Science. 7(57):1536-2442.

Interpretive Summary: Protein bait sprays, incorporating a toxicant, are one technique used for suppression of tephritid fruit fly populations. Effectiveness of the bait sprays, however, requires that they be applied in areas where the flies feed. Because GF-120 Fruit Fly Bait, a bait spray registered for tephritid fruit fly suppression in Hawaii, has limits on permitted application rate, ground applied bait sprays can not be applied as complete cover sprays, but applications must be targeted. Improved understanding of roosting behavior (i.e., where the flies choose to feed and seek shelter) of tephritid fruit flies is needed to improve the targeting of the bait sprays. In this study, we compared the attractiveness of potential border plants as roosting hosts for melon fly, Bactrocera cucurbitae, and oriental fruit fly, B. dorsalis. Plant species tested included windbreaks, broad-leaved ornamentals, corn (Zea mays), common weed species found in cucurbit-growing areas in Hawaii, several nonflowering/nonfruiting fruit tree species and one melon fly host crop (zucchini, Cucurbita pepo). Plants tested were established in pots and placed in clusters in an open field bordering a papaya orchard known to have well established populations of both fly species. Each plant cluster included a protein bait trap for capture of attracted flies. For melon fly, trap catch associated with castor bean (Ricinus communis) exceeded catch with any other plant species tested. Although castor bean is a weed species, it can be established along crop borders and maintained as a focal point for bait sprays. In addition to castor bean, other preferred roosting plants were the windbreaks panax (Polyscias guilfoylei) and wiliwili (Erythrina sandwicensis), and guava (Psidium guajava). For oriental fruit fly, catch associated with both panax and wiliwili was consistently high while castor bean, cocklebur (Xanthium strumarium), christmasberry (Schinus terebinthifolius), and ti leaf (Cordyline terminalis), as well as a number of different fruit trees were also used as roosting sites. Of the fruit trees, trap captures associated with guava plants were significantly higher than trap captures in the papaya orchard while trap captures associated with lemon (Citrus limon), avocado (Persea americana), orange (Citrus sinensis) and mango (Mangifera indica) trees exceeded, but were not significantly greater than, trap captures in the papaya orchard. Establishment of preferred roosting hosts as crop borders may help to improve suppression of both fruit fly species by providing sites for bait spray applications. Further research is needed to assess the use of vegetation bordering other host crops as roosting hosts, especially for oriental fruit fly.

Technical Abstract: The use of toxic protein bait sprays to suppress melon fly, Bactrocera cucurbitae (Coquillett), populations typically involves application to vegetation bordering agricultural host areas where the adults seek shelter (“roost”). Although 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, roosting by oriental fruit flies in borders of some crop species (e.g., papaya, Carica papaya), suggests that bait spray applications to crop borders could also help in suppression of B. dorsalis populations. In order to develop improved recommendations for application of bait sprays to border plant for suppression of melon fly and oriental fruit fly, we tested the relative attractiveness of potential border plants, in a vegetative (non-flowering) stage, to wild melon fly and oriental fruit fly populations established in a papaya orchard in Hawaii. Plants tested included windbreaks, broad-leaved ornamentals, corn [Zea mays], common weed species, locally grown fruit trees and one melon fly host crop (zucchini, Cucurbita pepo). Plants were established in pots and placed in an open field, in clusters encircling protein bait traps, about 66 feet away from the papaya orchard. We identified castor bean (Ricinus communis), panax (Polyscias guilfoylei), wiliwili (Erythrina variegate), 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. Guava had not previously been identified as a preferred roosting host for melon fly. Other than for the use of panax as a roosting host, there has previously been little attention to roosting hosts for oriental fruit fly. Establishment of preferred roosting hosts as crop borders may help to improve suppression of both fruit fly species by providing sites for bait spray applications. Further research is needed to assess the use of vegetation bordering other host crops as roosting hosts, especially for oriental fruit fly.