How Does the Application of Beauveria bassiana and Compost on Corn Crops Affect the Survival and Genetic Diversity of Phyllophaga obsoleta (Coleoptera: Melolonthinae)?

The knowledge of the diversity and genetic structure of pest insects under management contributes to the improvement of control strategies. An experiment was run to investigate whether the addition of the fungus Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) (BB) and compost to soil affects the presence and genetic diversity of adults and larvae of Phyllophaga obsoleta Blanch (Coleoptera: Melolonthinae) larvae in maize crops. We collected adults in and used mating pairs under four treatments (BB, compost, soil, blank). Genetic diversity and structure were determined through five allo/iso-enzymatic loci. Beauveria bassiana affected the presence and mortality of P. obsoleta in the laboratory but not under field conditions. The genetic diversity of P. obsoleta ranged from moderate to high (Ho = 0.26-0.31), with a low genetic differentiation among localities or treatments (Phi < 0.05), indicating high levels of gene flow. Our results showed a weak effect of B. bassiana on P. obsoleta in the field. Still, our laboratory observations suggest that the fungus may be a suitable alternative for biological control.