| The oriental fruit fly, Bactrocra dorsalis Hendel(Diptera, Tetriphitidate), is an important quarantine pest worldwide. In recent ten years, this fly has dispersed all over the South and Southwest China and created huge economic damage to fruit production. The potential distribution of this species may expand northward and to larger area. The Chongqing region lies in the upper reaches of Changjiang River, with the climate of hot summer, warm winter and abundant rain. The subtropical moist monsoon climate was thought be suitable for the oriental fruit fly. This fly is difficult to be eradicated if it established population, because of the wide host plant range, high reproductive potential and dispersal capacity. The eggs and larva of the oriental fruit fly in the fruits can expand with the human activities, the adults also have relatively high dispersal capacity. Along the process of invasion, the host plants of the oriental fruit fly may change, and the secondary host plant may become the main because of the rapid adaption to new host. To infer the influence of host switching on the oriental fruit fly, the selective propensity of the oriental fruit fly to six host fruits, the population dynamic of the oriental fruit fly and the activity change of several kinds antioxidase when transformed from banana to several main kinds of vegetables and fruit in chongqing, the content of the soluble sugar and protein, the relationship between the growth and development and the content of the nutriment were analysed. The results are as follows,1. The selective propensity of the oriental fruit fly to six host fruitsThe analysis of selective propensity of the oriental fruit fly to pumpkin, tomato, banana, orange, peach and cucumber was performed using the means of paper cup. The results showed that the egg laying amount on the six host fruits from the most to the least was:banana, peach, orange, tomato, pumpkin, cucumber. The egg laying amount on banana was the most and was significant lager than that on peach, cucumber and pumpkin; there was no significant difference of egg laying amount on banana, orange and tomato. The least amount of eggs was found on cucumber.2. The population dynamic of the oriental fruit fly on six host fruitsThe influence of host switching on the growth and development, and the reproductive potential of the oriental fruit fly was studied under the condition of 28±0.5℃, RH 70±5℃, and 14 L:10 D. The results showed that the survival rates and developmental periods of the egg, larva and pupa changed when transformed from banana to other five host fruits, and the index of growth and development were different among the five fruits. The developmental periods on orange and tomato were relatively short, and that on cucumber was the longest. The oriental fruit fly could complete life history on all of the five host fruits and all of the population trend index were bigger than 1. The high population trend index of the oriental fruit fly on orange and peach(90.73 and 77.96, respectively) indicated that the two plants might be the most suitable host of this fly among the studied five fruits. Although the population trend index on tomato, cucumber and pumpkin were lower by far than that on another two fruits, and were 13.90,9.02 and 5.13 respectively, the population size on the three hosts showed a increasing trend.The content of soluble sugar and protein of the six host fruits were tested, and the relationship between population growth and the content of the two energy materials were inferred. The results of energy materials content analysis showed that the content of soluble sugar were 6.03%,4.53%, 4.23%,4.25%,2.47% and 1.77%; the content of protein were 5.71%,6.44%,13.15%,18.64%, 15.45% and 15.01% in banana, orange, peach, pumpkin, tomato and cucumber, respectively. The correlation analysis indicated that positive correlations existed between population growth and reproduction and soluble sugar content, negative correlation existed between population growth and reproduction and protein content.3. The influence of host switching on antioxidase.The Peroxidase (POD), Catalase (CAT) and Superoxide dismutase (SOD) are important enzyme system in organisms to eliminate radicals and prevent from oxidation. The activities of the three antioxidases in larvas after feeding orange, peach, banana, tomato, cucumber and pumpkin were test using colorimetric method. The result showed that no significant difference of POD existed among the larvas feeding on six fruits. The significant difference of SOD and CAT was observed among larva feeding on six fruits. The highest activity were 9.834 U/mgprot,9.7840U/mgprot on orange and pumpkin, and no significant difference was observed between this two. The lowest activity of CAT were 8.0474 U/mgprot,6.1088U/mgprot,6.1628 U/mgprot on peach, banana and tomato respectively, also no significant difference were observed. The CAT activity of larvas feeding on cucumber was 8.3170 U/mgprot. |
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