Selection of global Metarhizium isolates for the control of the rice pest Nilaparvata lugens(Homoptera:Delphacidae)

摘要

BACKGROUND:This study was initiated to search for fungal candidates for microbial control of brown planthopper(BPH)Nilaparvata lugens Stal,to which little attention has been paid in the past two decades.RESULTS:Thirtgamma-five isolates of Metarhizium anisopliae(Metschnikoff)Sorokin and M.flavoviride Gams&Rozsypal from different host insects worldwide were bioassayed for their lethal effects against third-instar BPH nymphs at 25°C and a 14:10 h light:dark photoperiod at ca 1000 conidia mm~(-2).On day 9 post-treatment,mortality attributable to mycosis ranged from 6.5 to 64.2% and differed significantly among the tested isolates with no apparent relationship to their host origin.Only two BPH-derived M.anisopliae isolates from the Philippines(ARSEF456)and Indonesia(ARSEF576)killed>50% of the nymphs.Both isolates were further bioassayed for time-concentration-mortality responses of the nymphs to the sprays of 19-29,118-164 and 978-1088 conidia mm~(-2)in repeated bioassays.The resultant data fitted a time-concentration-mortality model very well.Their LC_(50)values were estimated as 731 and 1124 conidia mm~(-2)on day 7 and fell to 284 and 306 conidia mm~(-2),respectively,on day 10.CONCLUSION:The two M.anisopliae isolates are potential biocontrol agents of BPH for further research.This is the first report of the lethal effects of global Metarhizium isolates on the rice pest.