The use of palm kernel cake in the production of conidia and blastospores of Metarhizium anisopliae var. major for control of Oryctes rhinoceros

The yield of conidia and blastospores of Metarhizium anisopliae var. major produced on maize supplemented with palm kernel cake (PKC) was estimated. In maize supplemented with 5 g and 10 g of PKC, the fungus produced 4.3 g and 5.6 g of conidia respectively. This is significantly higher than the yield of conidia produced on maize alone, which was 2.03 g. The fungus produced submerged spores termed as blastospores, in a simple liquid medium consisting of glucose and PKC. The formation of blastospores during the fermentation process was monitored. The results showed that the young blastospores are round to ovoid, with 5.0-5.5 ?m in diameter and matured blastospores are commonly ellipsoid with dimensions ranging from 5.0-5.5 ?m x 12.5-15.5 ?m. The highest yield of the blastospores was 3.26 x 106 blastospores ml-1, produced at seven days after fermentation. The conidia and blastospores were equally effective in controlling the third instar larvae of the Oryctes rhinoceros. Sixteen days after treatment, both inocula killed 100% larvae, with infection of between 94.3% and 97.1%. The LC50 values for both inocula were almost similar, at 9.1 days for conidia and 9.5 days for blastospores. This study showed that PKC can be used as a supplement to produce conidia and blastospores of the fungus, M. anisopliae var. major, and that the blastospores are potential for the biocontrol of the rhinoceros beetle