Research On The Relationship Between Trichogramma And Ostrinia Furnacalis Using⁶⁰Co Radiation

Trichogramma ostriniae Pang et Chen and T. dendrolimi (Matsumura) are endophagous parasitoids of insect eggs. They are two most important species of parasitoids used in controlling O. furnacalis (Guenee) in China. Study found that the T. ostriniae parasitic O. furnacalis egg is higher, and the T.dendrolimi is lower. In this paper, taking two Trichogramma species and O. furnacalislCorcyra cephalonica as system, we investigated the relationship between T. ostriniaelT. dendrolimi and O. furnacalis by using multiparasitism and pseudoparasitism. The results are summarized as following:(1) T. ostriniae radiation dose selection. The minimum effective radiation dose is80Gy,80Gy radiation doses could sterilize but does not affect the parasitization behavior; The mortality of T. ostriniae reached a peak at4th day after radiation, and the second peak occurred at6th day. The pattern is different with that in CK. These results indicated that radiation affected the lifespan of T. ostriniae. Nutritions prolonged the longevity of radiated T. ostriniae females.(2) The fecundity of radiated T. ostriniae females in24h was significantly different from that in control for wasps of1-day and2-days old, but not for3-days and4-days old wasps. There was no significant difference in number of C. cephalonica eggs parasitized between radiation and control, whereas the total number of eggs laid per day by and number of egg residue in wasps was significantly different between treatment and control. When wasps were sequentially exposed to hosts in4days, the number of eggs parasitized by wasp at1st and2nd day was not significantly different between radiation and control, whereas it was at3rd and4th day. The development of C. cephalonica eggs parasitized by radiated T. ostriniae is different from those unparasitzed, the eggs were yellow at4th day and gradually become flat, finally can’t develop into larva of C. cephalonica or Trichogramma. (3) The turn of exposition of C. cephalonica eggs to radiated T. ostriniae and T. dendrolimi with time intervals of12,24,36and48h, respectively, did not affect the emergence rate of T. dendrolimi and the female ratio.(4) With O. furnacalis egg as host, no wasp emerged from O. furnacalis eggs parasitized by radiated T. ostriniae females. The emergence rate of T. dendrolimi from O. furnacalis eggs parasitized by T. dendrolimi was less than10%, whereas it increased to70%when the eggs were parasitized by radiated T. ostriniae and T. dendrolimi females in turn. The turn of parasitizations by two wasp species did not affect the female ratio of offspring of T. dendrolimi. With C. cephalonica eggs as host, except the treatment in which the host eggs was exposed only to radiated T. ostriniae females there were no significant differences in emergence rate and female ratio of offspring among other three treatments.