Evaluation of the biocontrol potential of various Metarhizium isolates against green peach aphid Myzus persicae (Homoptera: Aphididae)

Abstract

Twenty-three isolates of Metarhizium anisopliae (Metschnikof) Sorokin and M. acridum (Driver & Milner) JF Bischoff, Rehner & Humber from non-aphid host insects around the globe were evaluated for their aphid biocontrol potential, which is not well known. The apterous adults of green peach aphid Myzus persicae (Sulzer) were exposed to the fungal sprays of 11.5, 99 and 1179 conidia mm(-2) and blank control in three leaf-dish bioassays. All the tested isolates except one were proven to be infective to the aphid species at 21 +/- 1 degrees C and 14:10 h light:dark photoperiod, causing corrected mortalities of 10.1-95.3% at the high spore concentration. The data from ten isolates causing > 50% mortality at the high concentration were found to fit a time-concentration-mortality model well, yielding parameters for the estimates of their LC(50) and LT(50) that vary with post-spray time and spore concentration respectively. Four isolates of M. anisopliae (ARSEF 759, 4132, 2080 and 576) had LC(50) values of 44-80 conidia mm(-2) on day 8 and LT(50) values of 4.9-6.8 days at 100 conidia mm(-2), with 91-98% of the killed aphids being well mycotised after death. The Metarhizium infectivity to M. persicae differs greatly among the tested isolates. The four mentioned isolates with desired virulence and sporulation potential are excellent candidates for microbial control of aphids.