Laboratory evaluation of the entomopathogenic fungus, Metarhizium anisopliae for the control of the groundnut bruchid, Caryedon serratus on groundnut

The pathogenicity of five isolates of Metarhizium anisopliae to adult Carye don serratus was evaluated in the laboratory. All the isolates tested were virulent to the beetle but pathogenicity varied among the isolates. One iso late, CPD 4 was consistently superior to all other isolates in terms of mor tality of the beetle, protection of groundnut pods from damage, reduction i n progeny production and repellency to the beetle. At 10 days post-treatmen t, adult mortality treated with 0.1, 0.5 and 1.0g of dry conidia equivalent to 3.6 x 10(8), 1.8 x 10(9) and 3.6 x 10(9) conidia of isolate CPD 4 per 5 0 g of groundnut pods was 100% which did not differ significantly from piri miphos-methyl-treated pods at 10 ppm. At the lowest dosage of 0.1 g of coni dia per 50g of pods, damage in pods protected with isolate CPD 4 was 5% whi ch did not differ significantly from the 2% damage in pods protected by pir imiphos-methyl at 10ppm but significantly differed from damage in untreated pods which was 26%. Isolate CPD 4 caused complete reduction in progeny eme rgence at all dosages tested. It also exhibited some degree of repellency t o the beetle with percentage repellency values of between 40-79% at concent rations of 0.1-1.0g of conidia per 50g of groundnut pods. These combined vi rulence and repellency characteristics of this isolate may increase its pro tectant potential against C. serratus. (C) 2001 Elsevier Science Ltd. All r ights reserved.