Variation among Samplers using the Sweep Net for Lygus hesperus Adults in Cotton

The western tarnished plant bug, Lygus hesperus Knight, is a key pest of cotton in western production regions.  Although the sweep net is a standard sampling method for lygus adults, relationships between population estimates obtained using this method and actual population levels, and the factors that influence these relationships, are poorly documented.  Improved understanding of these relationships is needed for the development and application of meaningful treatment thresholds.  Recent reports suggest significant among-sampler differences in sweep net-based population estimates of the adult tarnished plant bug, Lygus lineolaris (Palisot de Beauvois).  These differences would seem to preclude meaningful comparisons of population estimates collected by different investigators.  We used a mark-release-recapture method and the standard sweep net to evaluate among-sampler differences in population estimates of L. hesperus adults.  Adult lygus, marked with fingernail polish to facilitate identification and prevent flight, were released into 10-m sample rows on the evening before 10-sweep samples were collected the following morning.  The experimental design was a randomized complete block with three replications of three treatments (sampler).  Separate experiments were conducted in two plantings each of Pima and Acala cotton.  Collections of marked bugs from each study were evaluated for effects of samplers, sample dates, and their interaction.  Although differences in lygus collections were observed among sample dates, no differences were detected in the population estimates by different samplers in any of the four tests.  These results demonstrate that sweep net technique can be sufficiently standardized to allow direct comparison of population estimates obtained by different samplers.