Zeolite substrate characterization for Metarhizium robertsii inoculation

For this study, zeolite powder served as a substrate for inoculating Metarhizium robertsii to demonstrate the biocompatibility between the entomopathogenic fungus and the zeolite mineral, as the initial step in developing a biological control agent. Our fungal strains were isolated from corpses of spittlebugs (Aeneolamia albofasciata, Hemiptera: Cercopidae) and were identified as M. robertsii based on sequencing of the Internal Transcribed Spacer regions ITS1 and ITS2. Zeolite was characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). XRD and EDS results indicate that zeolite consists of a mixture of Heulandite and Clinoptilolite. EDS analysis shows that oxygen, silicon, and aluminum are the primary chemical components of the zeolite powder, with calcium, magnesium, iron, sodium, and potassium present in smaller amounts. After five days of inoculation, SEM images reveal M. robertsii conidia on the porous surface of zeolite particles, along with hyphal formation. These findings suggest the potential for maintaining M. robertsii spores and mycelium alive within a zeolite substrate under laboratory conditions.