A study was conducted using two isolates of Paecilomyces fumosoroseus obtained from two farming localities in Trinidad – Aranguez and Macoya. The growth kinetics and pathogenicity of both isolates were studied in the laboratory at three temperatures: 200C, 250C and 300C. The growth rates of the isolates differed considerably at the different temperatures and localities with both the Aranguez and Macoya isolates at 250C and 20 0C respectively performing optimally based on the criteria of the present study. The Aranguez isolate was the most pathogenic to Bemisia tabaci at 250C with an LC50 of 3.19 x 104 spores/mL causing 50% mortality (LT50) in 2.39 days; while the Macoya isolate at 20 0C with an LC50 of 3.49 x 105 spores/mL caused 50% mortality and LT50 to Bemisia tabaci is 1.61 days. The results are discussed in relation to similar studies conducted elsewhere.