Study On Mass-rearing Of Fopius Arisanus And Biological Control Effects On Bactrocera Dorsalis In Orchards

Fopius arisanus (Sonan) (Hymenoptera: Braconidae) belong to the Opiinae subfamily. It is an egg-pupal parasitoid of Tephritid fruit flies which primarily parasitize the eggs and young first instars of the fruit flies. The mass-rearing of this parasitoids was studied based on the study of artifical oviposition dish and some biology and ecology of F. arisanus. The Mass-rearing technics process was built. The dispersal behavior of room-rearing F. arisanus and its parasite rate in the fields were studied, the results showed that this parasitoid can suppress the next generation population of oriental fruit fly Bactrocera dorsalis (Hendel).1. Effects of agar to water ratio on the parasite efficiency of F. arisanus was studied. The result showed that the parasite rate of F. arisanus increased with the increasing of agar ratio and reached a plateau at 1 part strip agar to 50 part tap water. Room rearing of F. arisanus from April 2007 to September 2008 was recorded. The percentage of parasitoids recovery was 37.5% before oviposition dish bettered and after that was 61.0%.2. Effects of the adults rearing density and host egg to female F. arisanus ratio on the offspring of F. arisanus were studied in laboratory condition. The results showed that the adults rearing density of F. arisanus is one of important factors to influence the female ratio of the offspring. When the adults rearing density were 300 pairs (♀:♂=1:1) per cage, the percentage of female offspring was 60.34%. The female offspring decreased with the adult rearing density increasing. When the adults rearing density increased to 700 pairs per cage, the percentage of female offspring was only 38.30%. The correlation between female offspring rate and adult rearing density assumed Y=-0.0501x+74.176, (R2=0.9456). When host egg to female parasitoid ratios was 5:1, the mean number of host pupae and parasitoids offspring recovery were 10.25 and 8.88. The yield of parasitoid offspring increased with host egg to female parasitoid ratios increasing and reached a plateau at 25:1.3. The effects of diet (sugar feeding), host provision on the longevity, fecundity and sex ratio of F. arisanus were investigated. The results showed that diets and host provision can significantly influence the adult longevity of F. arisanus. The mean longevity of adult female parasitoids was 37.8±1.1d when deprived of host eggs, which was only 19.2±3.8d when host eggs were provided. The adult longevity of female was no longer than one week whether host eggs were provided or not when honey was deprived. Honey + water Feeding can significantly enhanced the fecundity, and the female ratio of offspring was also significantly increased when fed with honey + water.4. Temperature also influenced the longevity and fecundity of F. arisanus. The adult longevity of the parasitoids shortened when the temperature increased within 19℃-31℃, and fecundity of female F. arisanus was enhanced with the temperature increased from 19℃to 25℃, and which depressed when temperature increased from 25℃to 31℃. The offspring of F. arisanus was male bias when the temperature was too higher or lower. The correlation between female offspring rate and temperature was Y=-0.681T2+34.128T-361.22 , (R2=0.9433).5. The impact of F. arisanus parasite on the survival of oriental fruit fly B. dorsalis was studied. Research was carried out applying dechorionation treatment, a non-destructive procedure that makes host eggshells transparent to microscopic observation without interfering with development. The results showed that parasitized host eggs were subject to a higher mortality than non-parasitized ones. Moreover, super-parasitized host eggs were subject to a higher mortality than normal parasitized ones during the egg stage. Few parasitoid eggs did not development to the adult stage. The death factors of host eggs were analyzed, the quality of the host egg and the wounds that the parasitoids parasitized and super-parasitized were the main factors result in the death of host eggs.6. The room mass-rearing of F. arisanus was carried out using the oriental fruit fly B. dorsalis eggs as the host. The equipment, the technic processes and the instructions of room mass-rearing which were the bases of biocontrol on oriental fruit fly B. dorsalis in the fields were described. 7. Interspecific competition between F. arisanus and local dominant species Psyttalia incise (Silvestri) was investigated at 25℃in the laboratory. The P. incise can not discriminate the hosts which had previously been parasitized at egg stage by F. arisanus. Most of the hosts died which parasitized by F. arisanus at egg stage first and parasitized by P. incise at larva stage second, and the eclosion of adult parasitoids from the host pupal finally were only F. arisanus.8. The distance and dispersal behavior of adult F. arisanus in the fruit orchards were studied. The results showed that F. arisanus advanced gradually from the released point. The parasitoid arrived on the fruit nearby the release point to detect and locate host, and then flew away to forage others. F. arisanus flew and dispersed mainly within a distance of 50m from the released point and only a few of individuals dispersed over 100 m. The parasite rate was more than 60% within 30m. The dispersal and parasitized behaviors of room reared F. arisanus were no difference in different space position.9. The parasitoids of room reared were released in the guava and star-fruit orchards at Fuzhou suburb in 2008. The parasite rate and the factors which influence the parasite rate were studied. The results showed that the mean parasite rate to the oriental fruit fly in guava orchard was 45.8% on trees and was 30.1% on the ground, and which in star-fruit orchards was 33.3% on trees and was 22.1%on the ground when the population of fruit fly were high in the fields. The parasite rate of the local dominant species P. incise was significantly lower than that of F. arisanus. The cage experiments showed that F. arisanus more like to forge and parasitize the eggs of the host which were concealed in the fruit on the tree than that on the ground. The parasitized rate was 61.1±2.7 when the female parasitoid to female fruit fly was 1:1, and which was increased with the increasing of parasitoid to fruit fly ratios.