Comparison of methods for estimating the prevalence of Neozygites floridana in Tetranychus urticae populations infesting strawberries.

Methods for measuring prevalence of Neozygites floridana in a Tetranychus urticae population collected from strawberries were developed and compared. T. urticae were extracted from leaves using a soapy water solution (0.5 ml washing detergent : 8 L water) and then placed into 80% alcohol for use in Methods 1 and 2. Method 1: N. floridana-sporulating T. urticae cadavers were observed and quantified under a compound microscope (40-80x). Method 2: Adult females were mounted in lactophenol cotton blue and observed for the presence or absence of N. floridana hyphal bodies under a microscope (200-400x). Method 3: Live T. urticae females were incubated at 25 degrees C and 75% RH and observed for mortality and N. floridana infection under a compound microscope (6.4-40x). Method 1 was the most time-efficient method and it also allows processing of samples as time permits. Method 2 quantified significantly higher fungal prevalence than Methods 1 and 3, but Method 2 is not considered to be reliable because hyphal bodies are difficult to detect. No significant differences were found between Methods 1 and 3.