Preliminary study of selected entomopathogenic fungi for corn leaf aphid, Rhopalosiphum maidis, control

Abstract: Rhopalosiphum maidis Fitch. (Hemiptera, Aphididae), corn leaf aphid, is a pest of maize (corn) and other related crops with worldwide distribution. This insect can infest all aboveground parts of the corn plant and cause serious damage to the yield. The aim of this study was to determine the pathogenicity of selected entomopathogenic fungi (Beauveria bassiana (Bals.-Criv.) Vuill., Isaria fumosorosea Wize and three different strains of Metarhizium anisopliae (Metschn.) Sorokin against R. maidis in the second nymphal stage under controlled conditions (23 °C temperature, 60% humidity). Maize local variety ‘Adjametis tetri’ was used for the assay. Maize seeds were grown in separate pots containing growth substrate mix. Two weeks old corn seedlings` stems and leaves were sprayed with suspension of entomopathogenic fungi at concentration 1.0 × 106 conidia/ml. Controls were sprayed with distilled water with 0.01% Tween 80 as a wetting agent. Ten minutes later, ten R. maidis aphids were confined on each corn seedling previously infested by fungal entomopathogens and pots were placed in micro-perforated polypropylene bags to avoid migration of the aphids from plant to plant. Aphid mortality and the progeny production were studied 7 days later. Four replicates have been done per treatment. Significantly high aphids’ mortality rate has been shown by B. bassiana and I. fumosorosea and relatively low influence was caused by M. anisopliae strains. Almost all studied fungi caused suppression in aphid progeny production, but in different extent. B. bassiana and strain MA2 caused highest suppression, while effect of strain MA3 on progeny production was not significantly different from the control sample. Number of aphids’ new generation after I. fumosorosea and MA1 treatment was almost the same.