The relations were determined between the number of flies “visually estimated on a grill count basis” and then actually counted with a Scudder grill on 2,850 fly attractant sites. Eight two-man teams of inspectors collected these data throughout the 1951 “fly” season in Phoenix, Arizona.
The visual estimate technique agreed with the grill method by the same inspector with a range of 69 to 89 per cent accuracy. Agreement between inspectors was 89 to 98 per cent using actual counts, and 75 to 91 per cent using visual estimates. By application of simulated field threshold values to indicate the necessity for control action, the inspectors, with the exception of one team for visual method, were in agreement.
The results of this study show that the “visual estimate” technique is a useful extension of the Scudder grill method for appraising adult fly densities.
The authors are particularly indebted to Dr. L. Otis Emik for assistance and advice on various aspects of this study.