苏云金杆菌H-14对蚊幼虫的毒力测定及现场防制效果

实验表明:苏云金杆菌 H—14对二龄淡色库蚊和中华按蚊幼虫具高度的毒杀作用,LC_(50)分别为9.6×10~(-6)和8.0×10~(-3)毫克/毫升,在4.0×10~(-2)毫克/毫升浓度,LT_(50)分别为18及51分钟。对中毒死亡后的四龄淡色库蚊幼虫的组织病理检查,中肠上皮细胞呈明显肿胀、变形、崩解、部分结构消失,染色亲和力减弱。菌液浓度320ppm 对柳条鱼无急性中毒现象。现场应用苏云金杆菌 H—14作防制3种蚊幼虫的试验,在0.11ppm 浓度,淡色库蚊幼虫密度在处理后24小时下降99.30%;在0.12～0.50ppm 浓度,三带喙库蚊和中华按蚊幼虫密度下降93.10～100%。该菌株显示是一种高效的微生物杀幼虫剂。

Application of Bacillus thuringiensis H-14 against Mosquito Larvae

The objectives of this research project were to determine the activity of Bacillus thuringiensis H-14 against mosquito larvae.The primary po- wder of B.t,H-14 was obtainsd from Institute Pasteur.Paris France.It showed greater activity against second instar Culex p,pallens larval (LC_(50)of 9.6×0~(-2)mg/ml)than against the same larval stage of Anopheles sine- nsis(LC_(50)8.0×10~(-3)mg/ml).When the second and fourth instar larvae offboth species were immersed respectively into the dilute suspension of 4.0 ×10~(-2)mg/ml,the LT_(50)for C.p.pallens was 18 and 54 minutes,and that of A.sinensis was 51 and 106 minutes.Cytopathological changes on the dead specimens examined showed that the cells of gut epithelium appeared swollen,distored and burt.B.T.H-14 showed no effects on larvivous fish Gambusia at higher doses.In Shanghai field tests in 1979,this biolo- gical agent,applied at 0.11 to 0.05 ppm per square mener in a variety of mosquito larval breeding habitats,produced 93.1 to 100 perent of mixee larval populations of C.p.pallens,C.tritaeniorhynehus and A.sinensis within 24 hours after treatment.The reason of different action of the ba- ericide against mosquito larvae in both laboratory and field tests was discussed in our paper.Based on the present studiesp we found that B. T.H—14 showed excellent activity against mosquito larvae.How to prolong the residual activity of this material remains to be further stu- died.