Emergence Trap and Sweep Net Sampling for Adults of the Potato Leafhopper from Alfalfa12

Abstract

Adults of Empoasca fabae (Harris) were sampled from alfalfa under varying field conditions by using a newly designed emergence trap, absolute density determinations, and the sweep net. Efficiency of the emergence trap in collecting adults was not significantly affected by wind, temperatures, or alfalfa height. However, decreasing solar intensity resulted in a significantly decreased efficiency as predicted by the equation, E = 0.87S^0.36 (E = efficiency, S = cal/cm²/min). At solar intensities greater than 0.8 cal/cm²/min, the emergence trap gave a good estimate (80%) of absolute density. Wind velocity and, to a much lesser extent, temperature were the 2 important variables affecting sweep net catches. When pendular sweeps were used, the relationship of sweep net catches to wind velocity was predicted by the equation, M = 0.075 (1.205)^w (M = sweep net conversion factor, W = wind speed (m/sec)). The ratio for pendular vs. 180° sweeps for adult E. fabae was 0.48:1. Absolute density ranged from 17.6–66.0 per m² and the average sex ratio of males to females was 1.5:1. Female leafhoppers were caught more frequently in sweeps and less frequently in emergence traps than expected, probably due to lessened flight activity of females relative to males.