Investigating on the potential of local isolates of entomopathogenic fungi as biological control agents against greenhouse whitefly Trialeurodes vaporariorum

The initial step to mass production and commercialization of native entomopathogenic fungal isolates includes collection as well as evaluation of their pathogenesis on the pest. This research aims to investigate the pathogenicity of 36 local fungal isolates collected from the Iranian Research Institute of Plant Protection, Tehran, Iran against greenhouse whitefly Trialeurodes vaporariorum. Due to the variation of the collected isolates volume, a preliminary screening test carried out on the fourth instars of a model insect Galleria mellonella. Based on the obtained results, the Beauveria bassiana A1–1 isolate showed the highest mortality with an average of 75%, followed by IRAN1787C, IRAN1751C, IRAN1395C, IRAN428C and IRAN441C with mean mortality rates of 57.50, 55, 52.50, 50 and 45%, respectively. Subsequently, the isolates were selected for evaluation of vegetative growth, sporulation and bioassay tests on greenhouse whitefly. In the bioassay test, five concentrations of the isolates (104, 105, 106, 107 and 108 conidia/ml) were tested on the third–instar of whitefly nymphs, and then the parameters LC50 and LT50 of the isolates were calculated. The highest vegetative growth rate belonged to IRAN428C, IRAN1395C, A1–1, IRAN1787C, IRAN441C and IRAN1751C isolates while the highest sporulation rate belonged to IRAN1787C, A1–1, IRAN428C, IRAN1395C, IRAN441C and IRAN1751C, respectively. The results showed that the A1–1 isolate indicated the lowest LC50 and LT50 values among all used concentrations. Moreover, its vegetative growth and sporulation ranked third and second among all the collected isolates, respectively. Therefore, the A1–1 isolate is being introduced as the most effective biocontrol agent to control greenhouse whitefly.