Preliminary Studies On Impact Factors Of Parasitoids Of Bactrocera Dorsalis(Hendel) For Host-finding

In order to improve the effectiveness of parasitic wasps on the biological control,in this study,three impact factors were selected from the perspective of insect chemical ecology.In the first aspect,we investigated the effects of methyl eugenol(ME)on host-finding behavior of parasitic wasps which was a theoretical basis for optimizing the roles of ME and parasitic wasps among comprehensive control strategies of Bactrocera dorsalis(Hendel).In the secord aspect,preliminary discussion on the role of volatiles from host plants in the host-finding behavior of Fopius arisanus(Sonan).In the third aspect,the morphology and ultrastructure of ovipositor and abdominal sensilla of four species of parasitic wasps,such as F.arisanus,Psytallia incisi(Silvestri),Diachasmimorpha longicaudata(Ashmead)and Fopius vandenboschi(Fullaway),were observed and studied by scanning electron microscopy(SEM)that conduce to research the mechanism of host-finding of parasitic wasps.The results were as follows:(1)Effects of ME on parasitic wasps.The results of Y-olfactometer showed that there were no significant differences in the selection reaction of mature F.arisanus and immature P.incisi between ME and control,while other parasitoids showed significant repellent response to ME.Attractant behavior activities occurred at the lower concentrations(0.01,0.1,1?l/ml)of ME,while repellent effects increased to a significant level as the concentrations increased(100,1000?l/ml).The highest EAG value of F.arisanus female occurred at 1 ?l/ml,while F.arisanus male at 10?l/ml.The results of Six-choice olfactometer showed that four parasitic wasps preferred to the lower concentrations of ME(0.1,1 ?l/ml)in the environment with different concentrations of ME.Meanwhile,compared to the control,the number of parasitoids attracted by the host egg traps was significantly decreased in the environment with(10,100,1000 ?l/ml)ME,and different concentrations of ME significantly affected the ovipositional behavior of F.arisanus female.(2)Behavioral response of F.arisanus to different treatments of host plants.Y-olfactometer bioassays showed that healthy,infected and mechanically damaged banana and orange significantly attracted mature females of F.arisanus,and the attraction of infected orange to mature females of F.arisanus was more significant than healthy orange,but different treatments of tomatoes had no attractive effect on F.arisanus female.On the third day after the orange infected and on the fifth day after the banana infected,the attractiveness was the strongest,while on the fifth day after the tomatoes infected,tomatoes had a significant repellent effect on the mature females of F.arisanus.Based on the results of behavioral responses,the composition of fruit volatiles from different host plants were analyzed by GC-MS.After infected by B.dorsalis,the infected fruits newly produce Leaf acetate,Trans-Farnesol,beta.-Ocimene,Benzaldehyde,cis-Thujopsene,Cedrol,Ethyl octanoate,Methyl octanoate,Tetradecane,Pentadecane and Eicosane hysteresis,Linalool and P-Myrcene were found in the second day and third day after orange infected,respectively,and the relative content increased gradually.(3)Eight kinds of sensilla were found on the ovipositor and abdomen of four species of parasitoids by scanning electron microscopy(SEM),respectively,were sensilla trichoidea,Bohm's bristles,sensilla campaniformia,slight surface depression,sensilla styloconica,sensilla coeloconical,sensilla chaetica and secretory pore.At the same time,the ovipositor speculas of F.arisanus and F.vandenboschi were tapering,while the ovipositor speculas of P.incisi and D.longicaudata were barb-shaped.