感染杨干象幼虫的高致病力虫生真菌菌株筛选

Screening of High Virulent Entomopathogenic Fungal Strains to Infect Larvae of Cryptorrhynchus lapathi(Coleoptera:Curculionidae)

【目的】筛选对杨干象幼虫具有高致病力的真菌菌株,测定防治效果,为生物防治提供依据。【方法】选用7株虫生真菌菌株对杨干象幼虫进行室内致病力测定,筛选出高致病力菌株并进行林间生防试验,对受侵染的杨干象幼虫的致病症状进行研究。【结果】1)用菌株CFCC87323以108conidia·m L-1分生孢子悬浮液处理杨干象幼虫,校正死亡率达93.38%,致死中时LT50为3.536天,致死中浓度LC50为7.0×103conidia·m L-1;林间生防试验采用108conidia·m L-1孢子悬浮液涂干法,校正死亡率达77.62%。2)用菌株ACCC30830以108conidia·m L-1孢子悬浮液处理杨干象幼虫,校正死亡率达81.46%,致死中时LT50为4.248天,致死中浓度LC50为5.43×103conidia·m L-1;林间生防试验采用108conidia·m L-1孢子悬浮液涂干法,校正死亡率达66.06%。3)用菌株ACCC30831以108conidia·m L-1孢子悬浮液进行室内生物测定,校正死亡率达73.51%;林间防治试验采用108conidia·m L-1孢子悬浮液涂干法,校正死亡率达58.48%。4)用菌株CFCC87327以108conidia·m L-1孢子悬浮液进行室内生物测定,校正死亡率达72.85%;林间防治试验采用108conidia·m L-1孢子悬浮液涂干法,校正死亡率达56.32%。5)观察杨干象幼虫感染的致病症状发现,杨干象幼虫被菌株CFCC87323侵染后,从出现明显症状到死亡变成僵虫需要(74.67±2.31)h,到虫体布满菌丝需要(93.67±3.21)h。【结论】白僵菌菌株CFCC87323对杨干象幼虫致病力最高,菌株ACCC30830次之。菌株ACCC30831和CFCC87327对杨干象幼虫也表现出较好的致病效果。

【Objective】Because larvae of Cryptorrhynchus lapathi bore and feed in tree trunk,it is very difficult to control this pest with chemical pesticides.In this study,we screened fungal strains with high pathogenicity to larvae of C.lapathi,and determined the control effect to provide the basis for biological control the pest.【Method】In this study,7entomopathogenic fungal strains were tested for pathogenicity to C.lapathi larvae in laboratory.The strong virulent strains were selected and used for infecting trials in the field.The pathogenic symptoms of infection were observed.【Result】1）The CFCC8732 conidiospore suspension at the concentration of l0-8 conidia·mL^-1 was used to infect larvae of C.lapathi.in lab,and the results showed that the adjusted mortality rate of C.lapathi larvae was 93.38%,the quickest median lethal times（LT_（50）） was 3.536 d,and the median lethal concentration（LC50） was 7.0 × 10^3conidia·mL^-1.In the field experiments,the conidiospore suspension with l08 conidia · mL^-1 was smeared on the tree trunk infested by C.lapathi larvae,and the results showed that the adjusted death rate of C.lapathi larvae caused by infection of strains CFCC87323 was 77.62%.2） The strain of ACCC30830 at the of concentration of l08conidia·mL^-1 was used to infect larvae of C.lapathi,and the adjusted death rate of larvae was 81.46%,the LT_（50） was 4.248 d and the LC50 was 5.43 × 10^3 conidia·mL^-1.In the field experiments,the conidiospore suspension with l0-8 conidia·mL^-1 was smeared on the infested trunk of C.lapathi larvae,and the adjusted death rate of C.lapathi larvae caused by infection of strains ACCC30830 was 66.06%.3） The strain of ACCC30830 conidiospore suspension at the concentration of l0-8 conidia·mL^-1 was used to infect larvae of C.lapathi in lab,and the results showed that the adjusted mortality rate of larvae was 73.51%.In the fieldexperiments,the adjusted mortality rate of larvae was 58.48%.4） The CFCC87327 conidiospore suspension at the concentration of l08conidia·mL^-1was used to infect larvae of C.lapathi in lab,the results showed that the adjusted mortality rate of larvae was 72.85%,In the field experiments,the adjusted mortality rate of larvae was 56.32%.5） As for the pathogenic symptoms,the time from the appearance of symptoms with infection of the strains CFCC87323 to dead body of C.lapathi larvae took（74.67 ± 2.31） h.From the beginning of infection by C.lapathi larvae to the hypha of strains CFCC87323 covering the whole body took（93.67 ± 3.21） h.【Conclusion 】The results indicated that strain CFCC87323 of Beauveria bassiana had strongest pathogenicity to C.lapathi larva and the strain ACCC30830 took the second place.The strains ACCC30830 and CFCC87327 also showed pathogenic effect to C.lapathi larva.This study provided a new way to safely and effectively control the population of C.lapathi and their damages to the plants.