Evaluation of different isolates of entomopathogenic fungus, Paecilomyces fumosoroseus (Deuteromycotina: Hyphomycetes) against Bemisia tabaci (Hemiptera: Aleyrodidae)

Bemisia tabaci (Gennadius) (Homoptera, Aleyrodidae) is one of the most important whitefly pests in different parts of the world including subtropical and tropical region as well as in the reenhouse production systems. In order to search for an effective biocontrol agent against this pest, we conducted this study to determine the effectiveness of the entomopathogenic fungus, Paecilomyces fumosoroseus against B. tabaci. The viability of P.fumosoroseus isolates conidia was determined by culturing them on potato dextrose agar (PDA) culture medium and assessing their germination after 24 h of incubation at 24 ±2 °C. Results of this experiment showed that percent of germination was 100, 100, 98 ±1, 97 ±1, 96 ±2, 100, 95 ±1, 100, 98 ±2, and 97 ±1 for isolates P.F.UPM, P.F.49, P.F.39, P.F.24, P.F.40, P.F.29, P.F.16, P.F.1, P.F.12, and P.F.2, respectively. Mortality of egg and nymph of B. tabaci caused by different isolates of P. fumosoroseus was studied under laboratory conditions using fungal conidia suspension with a concentration of 1×106 conidia mL-1. The mortality of B. tabaci eggs and second, third and fourth instars nymphs caused by the P. fumosoroseus isolates was from 42 to 91, 38 to 90, 37 to 89, and 41 to 86%, respectively. The P.F.UPM as the most lethal isolate caused 91, 90, 86 and 89% mortality on eggs and second, third and fourth instars respectively. Mortality caused by the other isolates ranged between 42 to 76%, 38 to 74%, 37 to 85%, and 41% to 84% for eggs and second, third and fourth instars respectively. There was a significant difference between various isolates for causing mortality on eggs and second, third and fourth instars respectively. According to the results, there was a strong correlation between mortality in all stages of B. tabaci life cycle and the fungal isolates. Conidia concentrations of P. fumosoroseus (UPM)isolate for concentration mortality response test were 1 × 108, 1 × 107, 1 × 106, 1 × 105 and 1 × 104 conidia mL-1. In the concentration-mortality response tests with the second instar nymphs mortality reached up to 95% within 6 days after application of conidia suspension at the concentration of 1×108 conidia mL-1 and there were significant differences among various concentrations. The Lc50 of this fungus against the second instar nymph of B. tabaci six days after application was determined as 2.77×105 conidia mL-1. The P. fumosoroseus isolate UPM obtained from B. tabaci was more effective against all stages of B. tabaci compared with the fungi isolated from Pteroma pendula. However, further studies have to be carried out to determine effectiveness of this isolate in the field conditions.