Safety evaluation of grandparent silkworm of F₁ hybrid reared with mulberry sprayed with mixed pesticides

【Objective】Purposes of this study was to evaluate the safety of the mixed application of omethoate EC, chlorpyrifos EC and propargite EC on mulberry for the grandparent silkworm of F₁ hybrid commonly used in Yunnan and provide reference for the pest control and scientific drug use in mulberry orchid in silkworm area.【Method】1500 times liquid of 40% Omethoate EC, 2000 times liquid of 73% Propargite EC, 1500 times liquid of 40% Chlorpyrifos EC mixed at 1:1:1 were sprayed on mulberry to prevent and control pests.Mulberry leaves picked on 10 and 14 d after pesticide application were used to feed eight species of grandparent silkworm of F₁ hybrid commonly used in Yunnan(Yuncan ₇A, Yuncan ₇B, Yuncan ₈A, Yuncan ₈B, Jingsong A, Jingsong B, Haoyue A, Haoyue B).The instar development, vitality score(cocoon formation rate and healthy pupa rate), cocoon quality score(total cocoon weight, cocoon layer weight and cocoon layer ratio) and egg quality score(good eggs per moth, bad eggs and total eggs) of eight species were investigated.【Result】The results indicated that using a mixture of three pesticides on mulberry trees did not cause any harm to mulberry.The developmental process of eight strains reared with leaves picked on 10 and 14 d after pesticide application had no effect, and there were no acute poisoning deaths.Feeding silkworms with mulberry leaves picked on 10 d after pesticide application had a great influence on vitality, cocoon quality and egg quality of Yuncan ₇A, Yuncan ₇B and Yuncan ₈B.There was no effect on the egg quality of Yuncan ₈A, but there was effect on the vitality and cocoon quality, and there was effect on the vitality and cocoon quality of Haoyue A.It had influence on the cocoon quality of Jingsong A, Jingsong B and Hao-yue B.Feeding silkworms with mulberry leaves picked on 14 d after pesticide application had an effect on the vitality of Haoyue A, but not obvious effect on the other seven strains.There was no obvious effect on cocoon layer ratio of the eight strains.The number of good eggs and total eggs laid by a single moth of Yuncan ₈B were significantly lower than that of the clear water control(P< 0.05), while those of other seven strains were not obviously influenced by it.【Conclusion】Feeding silkworms with mulberry leaves picked on 10 d after pesticide application affects vitality, cocoon quality and egg quality of the eight silkworm strains in different degrees.Feeding silkworms with mulberry leaves picked on 14 d after pesticide application has no significant influence on the vitality, cocoon quality and egg quality of other five strains, except Haoyue A, Yuncan ₈A and Yuncan ₈B.It is suggested that Yuncan ₇A, Yuncan ₇B, Jingsong A, Jingsong B, Haoyue B can be fed safely after 14 d of application.According to the vitality, cocoon quality and egg quality of silkworm, the sensitivity of different strains to mixed application of omethoate EC, chlorpyrifos EC and propargite EC are ranked as follows:Yuncan ₇B> Yuncan ₈B> Haoyue A> Yuncan ₇A> Yuncan ₈A> Jingsong B> Haoyue B> Jingsong A.