Response of entomopathogenic fungi to Relative humidity

Many entomopathogenic fungi have been screened for the development of myco-insecticide product against various insect pests but thier failure in the field have been attributed to environmental challenges. Thefore, development as microbial biopesticide products require selection of virulence strains which can tolerate abiotic factors known to be detrimental for fungi either during industrial production or in the field against target host pest. Our study was performed to investigate the effect of some environmental parameters on growth of two Cameroonian isolate, one M. anisopliae and one B. bassiana. Colony formation, mycelia growth and conidia production were assessed on PDA media at fourteen pH level (2 – 14), three photoperiods (continuous light, continuous dark, and 12h light/12h dark), five exposure time under UV light and four relative humidity levels (35, 50, 75 and 99 %). Results revealed that Cameroonian isolates successfully grew at acidic to alkaline medium with wide pH tolerance and optimum ranges. Light regimes affected mostly mycelia growth and fungi pigmentation which increased with the photophase extension. Cameroonian fungal isolates also exhibited high UVB tolerance with Beauveria isolate remaining active during all exposure time while Metarhium isolate did not form colonies at 45 min exposure under UVB light even when incubation time was extended by 6 days. Exposure to UV light pulse duration 30 min stimulated mycelia growth and conidia production for BIITAC6.2.2 and only mycelia growth for MIITAC11.3.4. Fungi development was found effective at low to high humidity with preference of moderate humidity environment for both strains. Climate change mitigation for the development of biopesticide is here discussed.