The Study On The Protein Bait Of Fruitflies (Diptera: Tetriphitidae)

The oriental fruit fly is a polyphagous pest. The adults of B. dorsalis deposit eggs into the fruit, the larvae eat into the fruit pulp, and then the infested fruits fallen and rotted. The occurrence of B. dorsalis not only leads to economic losses, but also presents a huge influence on its distribution and trade in endangered area, with a result of its consequential losses far exceeding the direct losses.As an important quarantine pest, B. dorsalis can be easily dispersed with the transportation of fruits, vegetables and flowers. Therefore, how to control this pest species to economic crops such as citrus fruits is an urgent issue now. Based on the method of protein bait selection, our object is to design an attractive protein to B. dorsalis and mix this protein with other active chemicals to get some different lures. Finally, we tested the trapping activities of these lures to B. dorsalis and Bactrocera (Tetradacus) minax (Enderlein) in the lab and field. The main results are displayed as follows:1. Bioassay Methods of protein bait established in the laboratoryBehavioral responses of B. dorsalis to methyleugenol and metabolites of microorganisms were studied using the Y-tube olfactometer and the large nylon cage. Our results suggested that little error was found in the behavioral response of B. dorsalis in the bioassays of the large cage, meanwhile, the attactant rates were higher than that in the Y-tube olfactometer. Accordingly, large cages were used to simulate outside circumstances to test the behavioral responses of B. dorsalis in our subsequent experiments.2. Selections on the protein bait against Bactrocera dorsalisTwelve kinds of proteins were used to be tested the behavioral responses of B. dorsalis to them in the large cages, respectively. The results indicated that the tested proteins had different attractant abilities to B. dorsalis. Among the tested proteins, panceas peptone, soy peptone, beef extract and PY culture medium performed greater attractive ability to female adults than to males. Tangible attractant effects can be found in protain X, with an attractant rate of 24.83% in the primary bioassays. Therefore, mixed lures were made with the protein X as the basic ingredient in the latter bioassays. In the secondary bioassays, we found that attractant rate was 39.33%.3. Bioassays on the protein baits with different compositons to B. dorsalis in the laboratoryBioassays on the different baits which was composed of protein X, a major ingredient, brown sugar, vinegar (white vinegar or black vinegar) and ammonium acetate. These materials were mixed in different ratios to get the different baits. Our results showed that brown sugar, vinegar (white vinegar or black vinegar) and ammonium acetate could synergize the attractive ability of protein X to B. dorsalis. Attractant rate of the bait contained brown sugar, protein X and white vinegar was 29.5%, that of the other bait contained brown sugar, protein X and ammonium acetate was 32.1%. Therefore, these results suggested that the best protein bait was consitituted by brown sugar, protein X and ammonium acetate.By comparing the number of trapped B. dorsalis adults of two baits, one was composed of 5g brown sugar:5g protein X:3g ammonium acetate:50mL water and the other contained 5g brown sugar:5g protein X:10 mL white vinegar, at the different time spot in 24 hours, we found that attractant rate of the two baits increased with the duration, and it reached at the highest point at the 24th hour. The average attractant rate of the first bait was 55%,57.6% of the adults trapped by this bait were female, but less males were trapped. In the bioassays on the second bait, we got two higher attratant rates at two time spots, they were 42% at the 22th hour and 48% at the 23th hour, respectively.45.7% of the trapped adults were female and the others were male. Consequently, we thought the best duration of the tested protein bait to evaluate the attractiveness of bait to fruit flies was not over 24 hours.4. Field bioassays on the bait made by protein X+brown sugar+ammonium acetateIn the field bioassays, a mixture of sugar and vinegar was designed as the contrast. Our results suggested that the bait, protein X+brown sugar+ammonium acetate, performed the highest attractant rate, and much more females were especially trapped by it. The percent of trapped females by this bait was 9.2 times than that in the contrast. The number of trapped B. dorsalis adults of the tested protein bait was 4.1 times than that of methyleugenol. Accordingly, the bait made by protein X, brown sugar and white vinegar was chosen as the best bait used in the latter bioassays.The largest number of oriental fruit flies were trapped by the above bait on the third day, which was 6.3 times than that in the contrast. The attractiveness decreased since the third day. The bait performed little attractiveness five days later, so the effective duration of this bait was five days.After 0.1%,0.5%,1%,2% of methyleugenol were added, respectively, the trapping activities of the protein bait was significantly improved in contrast with blank controls.Dichlorvos EC is an effective pesticide against pests. After 0.1%,0.2%,0.5%,1% dichlorvos EC were individually added into the above bait, the poisonousness of the bait was enhanced against the B. dorsalis adults.When 0.5% methyleugenol and 0.5% dichlorvos EC were simultaneously added into the above bait, either the trapping activity or the poisonousness of the bait was improved against B. dorsalis adults.5. The trapping acitivities of the protein bait to Bactrocera (Tetradacus) minax (Enderlein)The bioassays of the protein bait to Bactrocera (Tetradacus) minax (Enderlein) were conducted in three field sites. Our results demonstrated that the bait made by protein X, brown sugar and ammonium acetate was significantly attractive to this pest species. The quantity of trapped flies was almost 3.0 times than the contrast of sugar and vinegar. In a word, the bait contained protein X, brown sugar and ammonium acetate was ont only attractive to B. dorsalis but also to Bactrocera (Tetradacus) minax.