海南瓜实蝇致病细菌的分离鉴定及杀虫活性测定

Identification of Bacteria from Bactrocera cucurbitae(Coquillett) in Hainan and Determination of Its Insecticidal Bioactivity

从海南自然感病死亡的瓜实蝇上分离到1株对瓜实蝇高毒力的致病性菌株BC-hn,对其生防潜能进行评估。通过形态学观察、生理生化测定和16S r DNA序列测定分析,确定菌株BC-hn为黏质沙雷氏菌Serratia marcescens;用1×108 cfu/m L的菌悬液接种瓜实蝇进行室内杀虫活性测定,研究结果表明接种7 d后成虫的平均死亡率为81.2%;卵孵化抑制率为37.5%,幼虫平均死亡率为53.0%,对蛹羽化的抑制作用最小,平均死亡率24.0%。用浓度为1×104~1×108菌悬液处理瓜实蝇成虫,7 d后的LC50为1.16×106cfu/m L。对其他昆虫致病性测定发现,菌株BC-hn对菜蚜也有较高的致死作用,接种7 d后的死亡率为60.0%,但对供试的斜纹夜蛾、菜青虫、玉米螟和黄粉虫的死亡率均低于10.0%。菌株BC-hn对瓜实蝇成虫的毒力高,并对昆虫具有一定的专化性,具有较高的防治潜力。

A virulent strain BC-hn with high infectivity was isolated from naturally infected and dead Bactrocera cucurbitae collected from Hainan and evaluated for its insecticidal bioactivities. The strain BC-hn was identified as Serratia marcescens by morphological, cultural, physiological and biochemical tests, and 16 S r DNA sequences analysis. Bioactivity of BC-hn(1×108 cfu/m L)against B. cucurbitae and other insects were assayed in laboratory. Mortalities of B. cucurbitae adult, egg, larvae and pupa were 81.2%, 37.5%, 53.0% and 24.0% at 7 d post-treatment, respectively. When adults of B. cucurbitae were inoculated with concentrations of 1×104—1×108 cfu/m L of BC-hn, LC50 was 1.16×106 cfu/m L at 7 d post-treatment. The strain was also effective against Lipaphis erysimi larvae, resulting in a mortality of 60%, but not effective against larvae of Prodenia litura(Fabricius), Pieris rapae(Linnaeus), Pyrausta nubilalis(Hubern), Tenebrio molitor(L.), where mortalities were lower than 10%. These results show that BC-hn is host specific in virulence and highly virulent against adults of B. cucurbitae.