BIOLOGICAL CONTROL OF THE SPOTTED STEM BORER CHILO PARTELLUS (SWINHOE) (LEPIDOPTERA: CRAMBIDAE) WITH THE ENTOMOPATHOGENIC FUNGI1 BEAUVERIA BASSIA NA AND METARHIZIUM ANISOPLIAE

Abstract

The pathogenicity of ten fungal isolates of Beauveria bassiana and Metarhizium anisopliae
to second, third, fourth, fifth and sixth instar Chilo partellus larvae was studied. A single concentration
(JxlOS conidial ml) of each isolate was assayed against second instar larvae. Of the ten isolates tested, B.
bassiana (BB-Ol) and M. anisophae (PPRC-4, PPRc-19, PPRc-61, EE-Ol) were the most pathogenic indUCing 93
to 100% mortality. A single concentration of the five pathogenic isolates was furl;her tested against
third, fourth, fifth and sixth instar larvae. Second and sixth instar larvae were the most susceptible
stages to the pathogenic isolates suffering 97% and 98% mortality, respectively. The LTso values were
low for second instar (2 days) and sixth (4.8 days) instar larvae. Multiple concentration assays (1.25x106,
2.5xl07, 5xl07, and lx1()8 conidia I ml) were conducted against second instar larvae with three of the
most pathogenic isolates (PPRC-4, BB-Ol, EE-Ol). The LC50 was l.44xl03, 1.53x1Q4, and 3.12xlQ4 for BB-01,
PPRC-4 and EE-Ol, respectively. In a gJ!€enho{;.se trial, treatment of 3-week old maize seedlings with the
virulent isolates considerably reduced stem tunneling and deadheart formation by C. partellus second
instar larvae. The isolates, PPRC-4, ppRc-19 and PPRc-61 seemed to be the best candidates for further
development and testing under field conditions