Bionomics Of Bactrocera Tau(Walker) (Diptera: Tephritidae) And The Effect Of Foods On Population Dynamics

Bactrocera tau (Walker) is an important quarantine pest in vegetable and fruit tree which belongs to Diptera, Tephritidae, Bactrocera Macquart. It distributs overseas mainly in Southeast Asia and South Pacific Ocean. The South of China is the primary distribution area interiorly. B. tau has a large feeding extent, chiefly doing harm to pumpkin, loofah, balsam pear, cucumber, wax gourd, tomato, eggplant, hot pepper, citrus, pomelo, watermelon, pawpaw, and so on. The female adult cause mechanical damages with pierceing epidermis and oviposition inside the fruits by ovipositor. The larva does harm directly. It eats pulp inside fruit causing rot and lost the edible value. This study combinated the investigation outside and experiment inside. On the basic of study in biological characteristics of B. tau, using artificial diet and five hosts plant, such as loofah, cucumber, pumpkin, balsam pear and orange to research the effect on growth, development and reproduction of B. tau. At the same time, study the preference of larvae and adults to different hosts fruit. The main study contents and results show followed:1 The establishment of experimental population of Bactrocera. tau1.1 Collection and expertise of fruit fly in ChongqingCollected the larvae and adults in the vegetable plot and orchard in Wanzhou and Sorthwest Agricultural University for the laboratory raise and expertise. The results suggested that B. tau belongs to Diptera, Tepfritidae, Bactrocera Macpuart, and it is the superior species in Chongqing.1.2 Morphologic character of B. tauCombined with the former describe of B. tau, the morphologic character of e.very stage has been observed carefully and the separation standard of larva instars has been researched. According to the three obvious concentrations of larvae oral hooks length, the larva is separated to three instrars. The really measurement scopes are as follows, the first instar: 0.08-0.16mm; the second instar:0.21~0.29mm; the third instar: 0.35~0.43mm. But the length of the body can't be the standard of the instar separation.1.3 The establishment of experimental population of B. tau.Through the experiments in different foods, feeding equipment and experimental conditions, the laboratory feeding technology of B. tau has been studied, at the same time, the experimental population of B. tau established. Using lump pumpkin as food, 28±0.5℃ feeding temperature, 70±5% for relative humidity, L14:D10 for illumination cycle. This is the rather ideal environment for the growth and development of B. tau.2 The bionomics of/?, tau2.1 The natural population dynamics of B. tauThe result of luring indicated that B. tau undergoes several generations one year and generations lapped seriously. In Chongqing, it can be 3-5 generations one year and has two flourishing periods. The first period is in June-July, the second period is in September-October and the second period usually is more seriously.2.2 Feeding and oviposition preference of B. tau to different foodsThe trial results of larvae feeding preference showed that towel gourd was the most preferable food for B. tau larvae. Proportions of 1st and 3rd instar larvae feeding in towel gourd were 30.68% and 40.00% respectively. Proportions of 1st instar larvae feeding in orange and artificial diet were 3.14% and 5.68% only. There was no 3rd instar larvae feeding in orange and artificial diet. Oviposition preference of B. tau was in correspondence with feeding preference. Proportion of B. tau oviposition in towel gourd was the greatest, it's 44.88%. It's 1.46 times, 2.19 times and 11.39 times than the proportion of B. tau oviposition in cucumber, cushaw and balsam pear. There was no B. tau oviposition in orange and artificial diet.2.3 Behavioral science ofB. tauB. tau oviposites inside the fruit. The larva grows in the interior of fruits. When the larva develops to the last instar, it creeps out and falls down to earth. Then it looks for the suitable place to pupate. More than 70% larvae pupated in the 0~5cm soil depth, only 3.7% larvae become pupa in deeper soil depth more than 10cm. When the pupae were located in the 0~7.5cm soil depth, the eclosion rate were more than 90%. The eclosion peak of pupae was in 06:00-10:00 and the proportion of eclosion in this time was 85.8% all day. The adults developed to sexual maturation needed 8-15d after eclosion. Then, after l~2d of mating, the female started to oviposite. And the quantity of eggs perfemale oviposited each day is l~70granule unequal.3 Effect of different foods on growth, development and reproduction of B.tau3.1 Effect of different foods on growth, development and reproduction of B. tauFed B. tau on towel gourd, cucumber, cushaw, balsam pear, orange and artificial diet with the same feeding conditions. Trail results shwoed, under the conditions of 28±0.5℃,70±5%RH, L: D= 14: 10 and the same light intensity, development period of the larvae fed on towel gourd and cucumber were significantly shorter than others larvae fed on other foods, respectively 4.50d and 4.58d. Development period of larvae fed on balsam pear was the longest, it's 6.15d. When the larvae were fed on towel gourd, cucumber and cushaw, Survival rates of larvae were all above 80%, and had no remarkable difference among each other. The average survival rates of larvae fed on balsam pear, orange and artificial diet were notably depressed, 51.17%, 45.67% and 30.33% in turn. The average weight of larvae fed on cucumber was the weightest. It's 0.0180g. When larvae were fed on balsam pear, the average weight of pupa, female and male adults were the weightest It's 0.0156g, 0.0141g and 0.0117g, but there were no significant difference to the average weight of pupa, female and male adults when the larvae were fed on cucumber. When the larvae was fed on artifitial diet, the weight of larvae, pupa and adults were all the lightest. The quantity of oviposition female'1 and oviposition period were remarkably more or longer than the quantity of oviposition female"1 and oviposition period of the females fed on balsam pear, orange and artificial diet when adults were fed on towel gourd, cucumber and cushaw. The average longevity of the females fed on towel gourd was the longest, it's 57.79d. The average longevity of the females fed on balsam pear was the shortest, it's 18.89d. The longevity of males fed on balsam pear and artificial diet were remarkably shorter than the longevity of males fed on the other four foods. There were no significant difference existing in the development period of egg, survival rate of pupa and preoviposition period of B. tau fed on different foods.The age-specific life table of B. tau fed on different foods indicated that the trend index of B. tau population fed on towel gourd, cucumber, cushaw and balsam pear were 22.62, 31.69, 20.78 and 3.52 respectively. The trend index of B. tau population fed on orange and artificial diet were less than 1, it's 0.54 and 0.11 respectively.Several population parameters were got by analyzing the time-specific life table. The results showed, though the net production rate of B. tau population fed on cucumber was lower than the net production rate of B. tau population fed on cushaw, the greatest intrinsic rate of increase, shorter mean generation time and the shortest population double time of B. tau population mean that...