Confrontation bioassay between entomopathogenic fungi: Behavior and growth

Entomopathogenic fungi are an important tool in IPM as enviromentally friendly pesticides. However, the interactions  between entomopathogenic fungi are poorly known. Applications of combined species are made sometimes without knowledge of these interactions. We confronted  fungal species on artificial media to observe the interactions between them.Three fungi were evaluated; Beauveria bassiana, Metarhizium brunneum and Isaria fumosorosea. All possible  confrontations among them were made plus proper controls. Explants (9mm) for each fungus were placed onto Petri dishes with PDA plus yeast (5%). We measured the radius of the micelial growth in direction to the other fungal explants for 5 days.We evaluated the mean of diary growth. The ANOVAs showed some significant differences, Metarhizium growth was inhibited in combination with other fungi.We also observed abnormal, swollen hyphal growth, hyphal lysis and dark  pigment production on M.brunneum confronted with Isaria. This could explain an almost complete lack of M.brunneum sporulation that we have observed when the three fungi are mixed and applied in the field against Asian citrus psyllid, Diaphorina citri. Beauveria growth was not significatively influenced by confrontations. Eventually  Isaria overgrows both fungi. Isaria sporulates but delays its characteristic gray-pink pigmentation when it is growing over explants of Beauveria.