夾竹桃紅顏料(Phloxine B)對東方果實蠅(Bactrocera dorsalis)之毒效評估

Abstract

Tests were conducted to determine the toxic effects of phloxine B (a xanthene dye) to the Oriental fruit fly, Bactrocera dorsalis (Hendel). Dye-containing diets were made of 25 % yeast autolysate, 75 % sugar, and various concentrations of phloxine B (0.125 %, 0.25 %, 0.5 %, 1 %, 2 %, and 4 %). The tested adult flies were starved for 12 h prior to the experiment, and then allowed to feed on various diets for 4 h in the dark. After 4 h of feeding, these flies were separated into 3 groups with each group consisting of flies from all of the various groups fed different concentrations of dye. The 3 groups were then kept under the following conditions, respectively: (1) light first at an intensity of 8000 lux for 8 h, then dark, followed by a 12: 12 (L: D) h photoperiod throughout the remainder of the 72-h experimental period and fed a non-phloxine B diet; (2) complete darkness throughout the 72-h period and fed a non-phloxine B diet; (3) totally dark for 7 d with a phloxine B-containing diet. The results showed that in dye-fed flies kept under condition (1), 100 % mortality was observed after 1 h of exposure to the light in both sexes of flies fed previously with 4 % phloxine B. For the dye-fed flies kept completely in the dark and fed the non-dye food, no mortality occurred within 72 h. However, if the flies were kept completely in the dark but were fed the phloxine B diet, 100 % mortality occurred in the flies which had fed on 4 % phloxine B. These results indicate that phloxine B elicits light-independent toxicity in Oriental fruit flies; however, the light may have facilitated its toxic effects. In addition, female flies fed the dye laid fewer eggs. Our study suggests that phloxine B has the potential to be used as an environmentally friendly control agent for Oriental fruit flies, and further investigations should be carried out.