Timothy (Phleum pratense L.) is an important cool season forage crop in Western states, primarily purchased on aesthetic appearance. Thrips (Anaphothrips obscurus Müller) have been implicated in quality reduction of this forage, but integrated pest management (IPM) is minimal. This dissertation addressed several IPM tenets: reliance on sampling, thresholds, alternative management tactics, and an ecological understanding of the system. Several sampling methods were compared for statistical consistency across time of day and season in Chapter 1. Rapping timothy tillers inside a plastic cup was the most consistent and fastest sampling method. Thrips densities were higher in the upper portion of the plant. Macropterous phenotypes were produced in late spring and throughout the summer; they dispersed as the summer progressed. In Chapter 2, differential thrips populations were created with disruptive insecticides. Thrips reduced hay quality and economic thresholds were established. Tetranychid mite populations were flared when cyfluthrin was used, but populations were not always present. Both thrips and mites affected yield, but quality degradation was a more consistent and common problem in these studies. Spring burning was investigated as an alternative physical management tactic in Chapter 3. Burning reduced populations in the short-term, although long-term management potential is questionable. In Chapter 4, the importance of density-independent effects on wing diphenism was tested by enclosing populations of thrips on timothy without and with nitrogen. Six weeks after fertilization, nitrogen had a direct effect on wing diphenism and a higher proportion of macropterous thrips were produced. This result was also obtained eight weeks after fertilization, but at this point in the study the differences in diphenism could have resulted from either a direct effect of nitrogen or an indirect effect of nitrogen, because there were more conspecifics in the nitrogen-treated timothy. Finally, the appendices detail a study on the precision of two sampling methods, a study on the effect of cyfluthrin calendar sprays on thrips, and several pilot growth chamber studies which investigated the effect of maternal wing diphenism, conspecific density, and nitrogen on offspring wing diphenism.
|Advisor:||Godfrey, Larry D.|
|Commitee:||Parrella, Michael P., Putnam, Daniel H., Zalom, Frank G.|
|School:||University of California, Davis|
|School Location:||United States -- California|
|Source:||DAI-B 70/08, Dissertation Abstracts International|
|Subjects:||Ecology, Organismal biology, Agriculture|
|Keywords:||Anaphothrips obscurus, Applied ecology, California, Fall River Valley, Integrated pest management, Phleum pratense, Tetranychidae, Timothy, Wing polymorphism|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be