| Parasitoids conduct fitness tests to host before parasitism in egg parasitoids,this phenomenon is widespread,the number of parasitized host can reflect the suitability between host and parasitoid wasps.While one kind of Trichogramma wasps can parasitize a variety of host insects,for the same Trichogramma species,the suitability of different host species may be different,and affect the Trichogramma biological characteristics,such as body size,parasitic capacity.At the same time,the same host suitability of different kinds of Trichogramma wasps is different,the differences of host suitability of the combination of the different host-Trichogramma wasps affect the quality of the Trichogramma wasps.Even parasitoids or host geographic populations will also affect this fitness,and ultimately impact the Trichogramma control effect on target pest.In this study,in order to understand the relationship between the rearing host and egg load or between the female size and egg load of Trichogramma wasp,and the comparison of suitability for three Trichogramma wasps within two kinds of host,we studied the effects of rearing hosts on the female size and egg load of wasps of three Trichogramma species(T.dendrolimi,T.ostriniae,T.japonicum)using Corcyra cephalonica egg,Ostrinia furnacalis egg and Mythimna separata egg as hosts,respectively,and related factors for Trichogramma species,the results are as follows:(1)The egg load of wasps of three Trichogramma species increased as female age increased within 48 h after wasp emergence.At 48 h,egg load of three Trichogramma species reaches the maximum.The egg load of 72 h-old wasps was lower than that of 48 h-old wasps of the corresponding species except for T.ostriniae wasps emerged from C.cephalonica egg and T.dendrolomi wasps emerged from O.furnacalis egg.The egg load of T.dendrolimi wasps was the highest among three Trichogramma species of the same age when C.cephalonica egg were used as the rearing host,the egg load of T.dendrolomi were significantly higher than the egg load of T.japonicum.When the rearing host is O.furnacalis egg,egg load of T.ostriniae were significantly higher than egg load of T.dendrolimi and T.japonicum of the same age.While the host was M.separata egg,no significant differences in egg load happened among the three Trichogramma species.(2)At 48,72 h,the egg load of T.dendrolimi wasps emerged from C.cephalonica egg was significantly higher than that of the wasps emerged from O.furnacalis egg and M.separata egg.The egg load of T.ostriniae wasps emerged from O.furnacalis egg was significantly higher than that of the wasps emerged from C.cephalonica egg and M.separata egg.The egg load of T.japonicum wasps emerged from M.separata egg was significantly higher than that of the wasps emerged from C.cephalonica egg and O.furnacalis egg.Except T.dendrolimi emerged from M.separata egg at 72 h,there was a significant positive liner relationship between egg load and female size for the three Trichogramma species,and the relevance degree increased with female age.(3)We observed the total fecundity and lifespan of three Trichogramma species.When the rearing host was C.cephalonica egg or O.furnacalis egg,total fecundity of T.ostriniae was significantly higher than that of T.dendrolimi or T.japonicum.Total fecundity of T.japonicum emerged from C.cephalonica egg or O.furnacalis egg was not significant different.Whereas the result was opposite for T.dendrolimi and T.ostriniae.(4)Rearing host is C.cephalonica egg,lifespan of T.ostriniae was significantly longer than T.dendrolimi and T.japonicum,lifespan of T.dendrolimi and T.japonicum was also significant different.Rearing host is O.furnacalis egg,lifespan of T.ostriniae and T.dendrolimi was significantly longer than that of T.japonicum,while lifespan of T.dendrolimi and T.ostriniae was not significant different.In addition,the lifespan of T.ostriniae emerged from C.cephalonica egg was significantly longer than that of the wasps emerged from O.furnacalis egg,the lifespan of other two Trichogramma species was not significant difference between the two host speceis.(5)The evaluation of potential control of three Trichogramma species against M.separata egg showed that the parasitism rate by T.japonicum was the highest,followed by the T.dendrolimi and T.ostriniae held the least parasitism rate.Developmental time of T.japonicum was shortest.Female proportion of T.dendrolimi>Female proportion of T.Japonicum>Female proportion of T.ostriniae.The number of T.dendrolimi in per host egg was significantly higher than that of T.japonicum.Emergence rate of three Trichogramma species was not significantly different,in more than 95%.The present study indicated that T.dendrolimi and T.japonicum could be suitable biological control agent for M.separata egg.Effect of host to body size,egg load of Trichogramma wasps and the parasitic results of three Trichogramma species to hosts are associated with host suitability.Rearing hosts have a significant impact on body size,egg load of Trichogramma wasps,all results have a theoretical guidance for biological control of using Trichogramma wasps. |
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