Author
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Spurgeon, Dale |
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Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/10/2009 Publication Date: 10/5/2009 Citation: Spurgeon, D.W. 2009. Using Marked Lygus hesperus (Knight) (Hemiptera: Miridae) Adults to Evaluate Sweepnet Sampling in Cotton. Journal of Cotton Science. 13: 196-205. Interpretive Summary: In recent years the importance of plant bugs (Lygus species) as cotton pests has increased dramatically across much of the U.S. cottonbelt. This increase in pest status has accentuated the need for improved understanding of commonly used sampling methods. A system for marking, releasing, and recapturing adults of the western tarnished plant bug was devised and validated in Pima cotton. Adult bugs were marked with fingernail polish to facilitate their identification and prevent flight. Marked bugs released in sample rows at known population densities were then sampled with a sweepnet. Observations suggested most (>85%) released bugs remained in sample rows. Regression analyses comparing numbers of collected bugs to known population levels estimated the sweepnet collected about 21% of released bugs from smaller, less developed plants, and about 8% from more developed plants. Changing the sizes of the samples 10 to 20 sweeps improved the population estimates, but population estimates of Lygus adults in less developed plants were still better than in more developed plants. These results illustrate the utility of the mark-release-recapture approach for sampling studies of adult Lygus in cotton. This approach provides opportunities for improved evaluations of the influences on sweepnet sampling of factors such as time-of-day, plant development, and variation among samplers. Technical Abstract: The recently elevated pest status of Lygus spp. across much of the U.S. cottonbelt has accentuated the need for improved understanding of commonly used sampling methods. A mark-release-recapture method was devised and validated for use in sampling studies of adults of the western tarnished plant bug, Lygus hesperus (Knight), in Pima cotton (Gossypium barbadense L.). Adult bugs were marked with fingernail polish to facilitate their identification and prevent flight. Marked bugs released in sample rows at known population densities were then sampled with the standard 38-cm sweepnet. Observations suggested a large proportion (>85%) of released bugs remained in sample rows. Based on two sets of pooled regressions relating numbers of collected adult bugs to expected numbers (assuming 100% collection efficiency), estimated collection efficiencies of the sweepnet changed with cotton crop development from about 21.4% in smaller, less developed plants to 7.7% in more developed plants. Increasing the sample unit size from 10 to 20 sweeps improved fit of regression models for both sets of samples, but fit of the model corresponding to less developed plants was still better than for more developed plants. These results illustrate the utility of the mark-release-recapture approach for sampling studies of adult lygus in cotton, and suggest opportunities for its use in quantifying the influences of factors such as time-of-day, plant development, and variation among samplers on population indices provided by the sweepnet in cotton. |
