COMPARATIVE LABORATORY EVALUATION OF SPINOSAD AND PHLOXINE B AS TOXICANTS IN PROTEIN BAITS FOR SUPPRESSION OF THREE FRUIT FLY (DIPTERA: TEPHRITIDAE) SPECIES

Authors: McQuate, Grant; PECK, STEVEN - BRIGHAM YOUNG UNIV; Barr, Paul; Sylva, Charmaine

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2005
Publication Date: 8/20/2005
Citation: Mcquate, G.T., Peck, S.L., Barr, P.G., Sylva, C.D. 2005. Comparative Laboratory Evaluation of Spinosad and Phloxine B as Toxicants in Protein Baits for Suppression of Three Fruit Fly (Diptera: Tephritidae) Species. Journal of Economic Entomology. 98: 1170-1178

Interpretive Summary: Tephritid fruit flies are serious pests of fruit crops throughout the world. Suppression programs, in areas where these species are established, and eradication programs in areas of recent invasion, have typically entailed the use of protein bait sprays incorporating malathion. Although these sprays are effective, they are controversial because of concerns for adverse effects on human health and on nontarget organisms. Two potential more environmentally friendly alternative toxicants for use with protein baits for suppression or eradication programs are spinosad and the photoactive dye, phloxine B. There have, however, been no publications which present comparative laboratory toxicological bioassays of phloxine B and spinosad among different tephritid fruit fly species. Laboratory tests were conducted to assess the relative toxicity of these two toxicants for melon fly (Bactrocera cucurbitae), oriental fruit fly (B. dorsalis), and Mediterranean fruit fly (Ceratitis capitata) females. A field test was also conducted with oriental fruit fly females to compare these toxicants under outdoor light and temperature conditions, because effectiveness of photoactive dyes increases with increased light intensity. In laboratory tests, spinosad was found to be effective at much lower concentrations for all three fruit fly species. In comparison among species, Mediterranean fruit fly was found to be significantly more sensitive to spinosad than were melon fly or oriental fruit fly, whereas melon fly was found to be significantly more sensitive to phloxine B than were Mediterranean fruit fly or oriental fruit fly. The higher outdoor light and temperature conditions led to greater enhancement of effectiveness of phloxine B than of spinosad, but phloxine B concentration still had to be significantly higher than spinosad to generate comparable levels of mortality. Although both toxicants have been shown to give good levels of tephritid fruit fly population suppression in the field, comparable levels of population suppression for any of the three species tested here will require a much higher concentration of phloxine B than spinosad in the bait.

Technical Abstract: Spinosad and phloxine B are two more environmentally friendly alternative toxicants to malathion for use in bait sprays for tephritid fruit fly suppression or eradication programs. Laboratory tests were conducted to assess the relative toxicity of these two toxicants for Bactrocera cucurbitae, B. dorsalis, and Ceratitis capitata females. A field test was also conducted with B. dorsalis females to compare these toxicants under outdoor light and temperature conditions. In laboratory tests, spinosad was found to be effective at much lower concentrations with LC50 values at 5 h of 9.16, 9.03, and 4.30, compared to 250.0, 562.1, and 658.9 for phloxine B (27, 63, and 157 times higher) for these three species, respectively. In comparison among species, C. capitata was found to be significantly more sensitive to spinosad than were B. cucurbitae or B. dorsalis, whereas B. cucurbitae was found to be significantly more sensitive to phloxine B than were C. capitata or B. dorsalis. The higher outdoor light and temperature conditions reduced LC50 values for both toxicants, but led to greater enhancement of effectiveness of phloxine B than of spinosad, with the LC5o value for phloxine B (30.97) dropping to less than 10 times that of spinosad (3.20). Fly behavior, though, is likely to keep flies from being exposed to maximum possible outdoor light intensities. Although both toxicants have been shown to give good levels of tephritid fruit fly population suppression in the field, comparable levels of population suppression for any of the three species tested here will require a much higher concentration of phloxine B than spinosad in the bait.