The Infection Effect of Metarhizium anisopliae KMa0107 against the Larvae of Potato Tuber Moth, Phthorimaea operculella(Zeller)

The infection effect of the strain KMa0107 of Metarhizium anisopliae against the potato tuber moth larvae was tested in the laboratory by immersing larvae of different instars into conidia concentrations of the fungus. The mortality of the potato tuber moth caused by infection of M.anisopliae increased with the increase of the concentration of conidial suspension and the time after treatment. The highest concentration (1.15108 mL-1) treatment the mortality was 96.67%, 90.00% and 83.33% for 2nd,3rd, and 4th instar larvae on 7th day, respectively. The virulence of M. anisopliae to the potato tuber moth differed with larval stages. The susceptibility of the potato tuber moth larvae to M.anisopliae decreased in the sequence of 2nd instar, 3rd instar, and 4th instar. The estimated LC50 values of the 2nd instar on 7th day after treatment, the 3rd instar on the 5th day after treatment and the 4th instar on day 4th after treatment was 1.85106~1.10105,6.59107~2.41105 and 3.69107~5.85105 mL-1, respectively,while LC90 of 2nd,3rd, 4th instar larvae was 2.43108~1.44107,7.97108~2.93107, and 4.34109~6.89107 mL-1, respectively. The median letha ltime of M. anisopliae to the potato tuber moth larvae differed with different concentrations, LT50 values of all tested instars were shortened with the increase of concentration, the short LT50 for the 2nd instar, add the longest LT50 was for the 4th instars. LT50 value was 5.91~1.33, 4.18~1.67 and 5.14~2.42 d for the 2nd, 3rd and 4th instar larvae under the inoculation of 1.15105~1.15108mL-1 suspensions. The results suggested the strain KMa0107 of M. anisopliae showed a good infect effect against the larvae of P. operculella and with a well development potentiality for the of biological control agents for the biological control on P. operculella.