Abstract:

Eight isolates of P. fumosoroseus (Pfr116, Pfr612, Pfr2175 and Pfr153) and B. bassiana (Bb2880, Bb2860, Bb2861 and Bb2879) were bioassayed against M. Sanborni under laboratory conditions. Aphids on the leaves were separately exposed to conidial suspension spray under a Potter Spray Tower at the concentrations of 21-902 conidia/mm2 for the P. fumosoroseus isolates, or at 10-646 conidia/mm2 for the B. bassiana isolates. As a consequence, the cumulative mortalities were 17.4-100.0% for P. fumosoroseus and 37.3-100.0% for B. bassiana, respectively. The estimates of LC50 (unit: conidia/mm2) were 126 for Pfr116, 442 for Pfr612, 213 for Pfr153, 234 for Pfr2175, 155 for Bb2880, 86 for Bb2860, 99 for Bb2861 and 138 for Bb2879 on day 5 after exposure, respectively. The estimates of LT50 for the 8 isolates against the pest species decreased with higher conidial concentrations, and the differences among the isolates tended to decline with the increasing concentrations. At 150 conidia/mm2, the LT50 estimates ranged from 4.5 to 7.7 days for the P. fumosoroseus isolates and from 4.5 to 5.1 days for the B. bassiana isolates. Based on comparison of both LC50 and LT50 estimates, the isolates Bb2860 and Pfr2175 were desirable candidates with high virulence and fast infection to the aphid pest.