Variation among samplers using the sweep net for Lygus hesperus adults in cotton.

Authors: Spurgeon, Dale; Cooper, William - Rodney

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/7/2010
Publication Date: 4/29/2010
Citation: Spurgeon, D.W., Cooper, W.R. 2010. Variation among samplers using the sweep net for Lygus hesperus adults in cotton. National Cotton Council, Memphis, TN. pp. 1219-1224.

Interpretive Summary: The sweep net is a standard sampling method for adults of the western tarnished plant bug in cotton. Improved understanding of the factors that influence the ability of the sweep net to capture plant bugs is needed to refine monitoring and management methods. Recent reports suggest different persons sampling plant bugs with the sweep net obtain different population estimates. If that is the case, it will be difficult to standardize sampling methods or to develop treatment rules that can be consistently applied. We marked adult plant bugs with fingernail polish so they could be identified, and to prevent their flight. Known numbers of marked bugs were released into rows of cotton, which were later sampled with the sweep net by three different samplers. Two separate experiments were conducted in cotton planted in mid-April; one experiment in Upland cotton, and one in Pima cotton. Both experiments were repeated in cotton planted during early-June. In each experiment, the numbers of marked plant bugs were compared among the three samplers, and among individual sample dates. Although the numbers of marked plant bugs collected differed among sample dates in three of the four experiments, the numbers collected by different samplers were always similar. These results show that the sweep net sampling method can be standardized so that different samplers may consistently obtain similar population estimates.

Technical Abstract: The sweep net is a standard sampling method for adults of the western tarnished plant bug, Lygus hesperus Knight, in cotton. However, factors that influence the relationship between true population levels and population estimates obtained using the sweep net are poorly documented. Improved understanding of these factors is needed for the development and application of refined 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 (Gossypium barbadense L.) and Acala (G. hirsutum L.) cotton. Collections of marked bugs from each study were evaluated for effects of sampler, sample date, and their interaction. Although differences in lygus collections were observed among sample dates in some tests, no differences were detected in the population estimates by different samplers. These results demonstrate that the sweep net technique can be sufficiently standardized to allow direct comparison of population estimates obtained by different samplers.