| Trichogramma chilonis and T.dendrolimi are the two most commonly used Trichogramma species,both of which can be mass produced with Antheraea pernyi eggs.But problems,such as low parasitic rate and emergence rate,often occur in the production of T.chilonis,and has been hindering the large-scale promotion and application of T.chilonis.This study explored the multi-parasitic breeding of T.chilonis and T.dendrolimi in the A.pernyi eggs and the storage method of multi-parasitic Trichogramma.The results of research showed that when using multi-parasitism to breed two Trichogramma species,it was recommended that the ratio of T.chilonis to A.pernyi eggs is 1:20-1:25,and the ratio of T.dendrolimi to A.pernyi eggs is 1:70.When Trichogramma develops to the mid to late stages of the larvae,it should be kept at 3℃for cold storage,and the time should be limited within 32 d.The best induction temperature for multi-parasitic Trichogramma is 12℃,and after induction for more than 30 d.1.Biological characteristics of T.chilonis and T.dendrolimi produced by multi-parasitism in A.pernyi eggsThe ratio of T.chilonis to fresh A.pernyi eggs is 1:10,1:15,1:20,1:25,1:30 and the ratio of T.dendrolimi to fresh A.pernyi eggs is 0,1:70,and 1:50,respectively.Investigate indicators including the parasitism proportion,emergence proportion,number offspring per egg,number of females of T.chilonis,and proportion of unemerged parasitoids.The results of research showed that the parasitism proportion and emergence proportion of multi-parasitisim were significantly higher than that of mono-parasitism of T.chilonis.When the ratio of T.dendrolimi was 1:50,the parasitism rate of multi-parasitism was above 96.54 %,but it was easy to cause superparasitism and affected the quality of Trichogramma products.When the ratio of T.chilonis to fresh A.pernyi eggs was 1:10,the number of unemerged parasitoids increased significantly,while when the ratio was 1:30,the number of female of T.chilonis was significantly lower than other ratios.To sum up,in multiparasitism,the best ratio combination was the ratio of T.dendrolimi to fresh A.pernyi eggs was 1:70,and the ratio of T.chilonis to fresh A.pernyi eggs was 1:20-1:25.When using this ratio to breed multi-parasitic Trichogramma,the number of female T.chilonis was42.56,which was 56.17% of the female T.chilonis,But compared to only breeding T.chilonis,the parasitic rate can be increased by 15.93%,the emergence rate increased by 8.45%,and the number of single-egg Trichogramma increased by 6.96.2.Effect of cold storage time on biological characteristics of multi-parasitismThe multi-parasitism of T.chilonis and T.dendrolimi,and the mono-parasitism of T.chilonis and T.dendrolimi were refrigerated at 3℃,respectively.for 0-60 d.Comparison of indicators such as emergence rate,number of offspring per egg,percentage of female Trichogramma,proportion of unemerged parasitoids,deformed adults proportion,longevity,and number of host eggs parasitized.Our data showed that when refrigerated for 0 d,the emergence rate of multi-parasitism and mono-parasitism were all above 90%,with the extension of cold storage time,the emergence rate showed a obvious decrease.When refrigerated to 40 d,the emergence rate of multi-parasitism and monn-parasitism were significantly lower than that without cold storage.The number of offspring per egg and the female proportion did not change significantly with the extension of refrigeration time among different treatments.The proportion of unemerged parasitoids showed a significant upward trend with the extension of refrigeration time.When multi-parasitic Trichogramma,T.chilonis and T.dendrolimi were refrigerated to 40 d,8 d,and 24 d,respectively,the proportion of unemerged parasitoids was significantly higher than that of cold storage for 0 d.The deformed adults proportion of multi-parasitism was no significant differences with the extension of refrigeration time(12.09%-14.02%),the deformed adults proportion of mono-parasitism refrigerated for 8 d and 24 d were significantly higher than that of cold storage for 0 d.The longevity and number of host eggs parasitized of multi-parasitism and mono-parasitism showed a significant decline with the extension of refrigeration time.The multi-parasitic T.chilonis refrigerated to 40 d and its lifespan is significantly lower than 0 d refrigerated,refrigerated to 24 d the egg production of single Trichogramma is significantly reduced;Comprehensive indicators,when Trichogramma is multi-parasitic in factory production,the refrigeration time should not exceed 32 d.3.Effect of different temperature and induction duration on diapause of multi-parasitism.The multi-parasitic Trichogramma,T.chilonis and T.dendrolimi bred separately was induced at four temperatures(8℃,10℃,12℃ and 14℃)for 10-40 d.Comparison of diapause rate research indicateed that both temperature and induction duration had a significant effect on the diapause of Trichogramma,and the interaction between the these two factors also had a significant effect on the diapause of Trichogramma.When the induction temperature was 12℃,the effect of inducing diapause was the best,at 30 d and 40 d,the diapause rate could reach67.85% and 8.18%,significantly higher than 10 d and 20 d treatments,followed by 8℃,after 40 days of induction,the diapause rate can reach 65.02%,no significant difference from 30 days,but significantly higher than the 10 d and 20 d treatments.At 14℃,the multi-parasitic Trichogramma induced diapause rate was the lowest,the highest was only 14.81%.It can be seen that the optimal induction temperature for multi-parasitic Trichogramma is 12℃,and the induction time is 30 d-40 d.When diapause was induced for 40 days,the diapause rate of multi-parasitic Trichogramma,T.chilonis,and T.dendrolimi was compared,The results of research showed that at 8 ℃ and 12 ℃,the diapause rate of multi-parasitic Trichogramma was65.02% and 68.18%,which were significantly higher than the treatments at 10 ℃ and 14 ℃.There are significant differences in the diapause rate of T.chilonis at the 4 temperatures,and the diapause rate at 8 ℃ is 69.19%,which is significantly higher than the treatments at 10 ℃,12℃ and 14 ℃.At 10 ℃ and 12 ℃,the diapause rate of T.dendrolimi was 93.55% and 97.29%,which were significantly higher than those treated at 8 ℃ and 14 ℃.At 8 ℃,there are significant differences in the diapause rate among the Trichogramma spp.T.dendrolimi is the highest,followed by T.chilonis,and the multi-parasitic Trichogramma is the lowest,only65.02%.At 10 ℃,12 ℃,and 14 ℃,the diapause rate of T.dendrolimi was significantly higher than that of T.chilonis and multi-parasitic Trichogramma,but there was no significant difference between T.chilonis and multi-parasitic Trichogramma difference. |
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