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Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains ix, 103 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 77-79).

Soybean, Glycine max (L.) Merr., is planted across a vast amount of land in the Mid-Southern U.S. (Arkansas, Louisiana, Mississippi, and Tennessee), and yield responses to defoliation can vary. Experiments were conducted during 2015-2017 evaluating how soybean yield responds to multiple and continuous defoliation, as well as planting date and plant population. Multiple defoliation events were evaluated by defoliating soybean at varying levels at V3, V6, and both growth stages. There was no interaction between defoliation occurring at V3 and V6 growth stages, indicating that the impact of each defoliation event was independent of the other. The effect of continuous defoliation was evaluated by defoliating soybean weekly, beginning at V2. Defoliation continued throughout the vegetative growth stages or throughout the entire growing season, and was compared to the same defoliation level occurring one time at R3. Continuous defoliation during vegetative growth stages only, did not reduce yield at any of the levels tested. Defoliation occurring throughout the growing season reduced yields more than a one-time defoliation event at R3, but only when defoliation levels exceeded the 20% defoliation threshold. This indicates that thresholds do not need to be modified to account for multiple or continuous defoliation. To evaluate the effect of planting date on yield loss from defoliation, soybean was planted at six planting dates beginning in early-April and continuing through mid-June. Each planting date included a defoliated treatment and an undefoliated control. It was determined that later planted soybean lose a greater amount of yield than earlier planted. Higher yielding soybean also lost more yield than lower yielding soybean at every planting date until Mid-June. It was concluded that late planted soybeans could benefit from a lower treatment threshold. The effect of plant population on yield loss from defoliation was evaluated by planting soybean at five populations ranging from 123,500 seeds/ha to 420,070 seeds/ha. A undefoliated control and a defoliated treatment was included for each plant population. Defoliation significantly reduced yields only where final plant populations were lower than 192,800 plants/ha. This indicates that fields with substandard plant populations are more susceptible to yield loss from defoliating pests.

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Thesis (M.A.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xi, 80 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references (p. 72-77).

Thesis (M.S.)--Oregon State University, 1983. / Typescript (photocopy). Includes bibliographical references (leaves 109-114). Also available on the World Wide Web.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

The effect of defoliation intensity and season on Douglas-fir growth were studied in three replications in the Siuslaw National Forest during 1988-1990. Four intensities of defoliation were applied once in either spring or summer 1988. Stem diameter and canopy area were linearly inversely proportional to the level of defoliation. Defoliation intensity did not affect height growth (P > 0.05). Greater losses in height occurred when seedlings were defoliated in spring than in summer. No differences in predawn and mid-day xylem water potential were observed between trees defoliated in summer or spring 1988. However, in 1989, 25% defoliation reduced mid-day moisture stress whereas 50 and 75% defoliation increased mid-day moisture stress (P < 0.05). Effects of defoliation on length, width, and area of dominant and subdominant twigs as well as number of twigs were separated into different whorls. As indicated by the sharp slopes of the response surfaces, spring defoliation affected seedlings more (P < 0.5) than summer defoliation. No season or intensity effects (except second whorls) on area of dominant twigs were carried over to 1990. No effects (P > 0.5) of season or intensity on twig width were observed in 1990. Subdominant twigs were generally more sensitive to defoliation than dominant twigs. Greater losses (P < 0.5) in area of subdominant twigs occurred when seedlings were defoliated in spring than in summer. Similar to area, length of twigs continued to respond to defoliation intensity in 1990. Length and width of dominant and subdominant twigs were smaller for spring compared to summer defoliated trees. Number of twigs were linearly inversely proportional to the level of defoliation intensity in 1989. Intensity did not affect number of twigs in 1990 except second whorls. No effect of defoliation intensity and season on new whorls was detected. / Graduation date: 1992