Food consumption by Chilo partellus (Lepidoptera: Pyralidae) larvae infected with Beauveria bassiana and Metarhizium anisopliae and effects of feeding natural versus artificial diets on mortality and mycosis

Abstract

Second and third instar Chilo partellus larvae were infected with Beauveria bassiana and Metarhizium anisopliae (both at 1 × 10 8 conidia/ml) and daily consumption of maize leaves was measured. Infection by the fungi was associated with reduced mean daily food consumption. Reduction in food consumption became evident 3–4 days after treatment with the fungi for second instar larvae and 4–5 days for third instar larvae. Four conidial concentrations, 1 × 10 5, 1 × 10 6, 1 × 10 7, and 1 × 10 8 conidia/ml, were tested against second instar larvae. Food consumption dropped by 70–85% when the second instar larvae were treated with the fungi at 1 × 10 8 conidia/ml. Reduction in food consumption by C. partellus larvae infected with B. bassiana and M. anisopliae may offset the slow speed of kill of the fungi. The effect of artificial versus natural diets on mortality and mycoses of second instar larvae treated with the fungi at 1 × 10 8 conidia/ml was determined. Larvae provided with artificial diet suffered little mortality and mycoses than larvae provided with maize leaves. The LT 50 was longer for larvae provided with artificial diet.