Efficacy of entomopathogenic fungi against three major stored insect pests, Rhyzopertha dominica, Sitophilus zeamais and Trogodermagranarium

Abstract

The use of biological control agents such as pathogens and natural enemies could be helpful in reducing reliance on synthetic non-selective insecticides and environmental pollution. Entomopathogenic fungi act as pathogens for insect pests and could be a good alternative to insecticides. In the present work, control potential of six native entomopathogenic fungi: Aspergillus nidulans, Aspergillus fumigatus, Cladosporium cladosporioides, Metarhizium flavoviride, Penicillium citrinum and Trichoderma harzianum, was evaluated against three major stored insect pests, Rhyzopertha dominica, Sitophilus zeamais and Trogoderma granarium, under laboratory conditions. Four doses of each fungal isolate viz., 1 × 104, 1 × 106, 1 × 108 and 1 × 1010 conidia/kg wheat grains were evaluated in terms of adult mortality and progeny suppression of subsequent generation. Bioassays were performed in an incubator with 30 °C, 65% relative humidity and without lighting, and the vials were observed after 7, 14, and 21 d post exposure to calculate mortality of introduced adults. The results revealed that insects’ mortality was dose and time dependent. In most of the cases, M. flavoviride caused the highest mortality and progeny suppression of all tested insect species followed by T. harzianum and C. cladosporioides, while the lowest were observed against A. nidulans followed by A. fumigatus and P. citrinum. Overall, R. dominica was the most susceptible species to all fungal isolates followed by S. zeamais and T. granarium. In summary, the data of the present work indicate a significant potential of tested entomopathogenic fungi as biological control agents against R. dominica, S. zeamais and T. granarium. Further studies are recommended to evaluate control potential of these entomopathogenic fungi against stored insect pests under storage environment. Evaluation of more virulent strains of entomopathogenic fungi and their isolates, development of suitable formulation(s), and standardizing mode application will also be the questions for future research.