Absolute-Density Estimation from Sweep Sampling, with a Comparison of Absolute-Density Sampling Techniques for Adult Potato Leafhoppper in Alfalfa1

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Abstract
A study of sampling techniques for adults of Empoasca (abae (Harris) in alfalfa was undertaken to derive ahsolute-density estimates from sweep-net sampling. A comparison of three absolute-density techniques showed that either the D-VacR or a modified EchoR suction device, operated with a small drop trap, yielded accurate estimates upon which the relationship of sweep-net catch and absolute density suhsequently was hased. Large drop trap sampling may be highly influenced by the density and uniformity of the alfalfa stand. Sampling several meters in front of the individual to avoid disturhing potato leafhoppers, compared with sampling immediately in front of the individual, gave no measurable advantage. Sweep-net sampling in fields that had been cleanly harvested yielded precise estimates of absolute density, using the equation x = IX.5y, where x = adult potato leafhoppers per m2 and y = catch per sweep. Distribution of five-sweep samples in cleanly harvested fields followed a Poisson series, and optimum sample size curves were determined. Harvesting of a portion of an alfalfa field altered the spatial distribution of potato leafhopper adults.