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dc.contributor.authorOjiambo, Peter Sande
dc.date.accessioned2014-03-03T23:10:03Z
dc.date.available2014-03-03T23:10:03Z
dc.date.issued2004-12
dc.identifier.otherojiambo_peter_s_200412_phd
dc.identifier.urihttp://purl.galileo.usg.edu/uga_etd/ojiambo_peter_s_200412_phd
dc.identifier.urihttp://hdl.handle.net/10724/22196
dc.description.abstractSeptoria leaf spot, caused by the fungus Septoria albopunctata, is a disease of increasing concern to the blueberry industry in Georgia and other southeastern states. Due to critical gaps in knowledge on disease ecology and epidemiology, current disease management guidelines are highly empirical. With this in mind, a series of field studies was carried out from 2001 to 2004 to generate key epidemiological information on temporal disease progression, seasonal inoculum dynamics, and the effects of disease on premature defoliation and yield. Additional studies were carried out to develop improved disease assessment and sampling procedures. Disease onset on rabbiteye blueberries grown near Athens was observed between late April and mid-June, and disease severity increased rapidly and reached a maximum by mid- to late September; thereafter, disease severity decreased until the end of the season. Disease severity was highest on early-emerging leaves and on leaves located on shoots closer to the ground. Pycnidiospore inoculum was present throughout the season, and leaves became infected by S. albopunctata season-long. Disease severity, defoliation, flower bud set, and return yield were found to be interrelated. Leaves with high disease severity at harvest abscised earlier in the fall than leaves with low disease severity, and shoots with severely diseased leaves and/or high levels of defoliation had a reduced potential to set flower buds. Furthermore, such shoots consistently had low return yields the following year. These results form the basis for identifying specific disease severity or defoliation levels that can be tolerated during specific periods of crop development without negatively impacting flower bud set and return yield. Based on the data collected in this multi-year field study, hierarchical sampling plans were developed for assessing disease severity and defoliation; these plans will be useful for obtaining reliable estimates of the two variables with the least expenditure of time.
dc.languageeng
dc.publisheruga
dc.rightspublic
dc.subjectBlueberry
dc.subjectDefoliation
dc.subjectDisease assessment
dc.subjectEpidemiology
dc.subjectInoculum dynamics
dc.subjectSampling
dc.subjectSeptoria albopunctata
dc.subjectSeprotia leaf spot
dc.subjectSurvival analysis
dc.subjectTemporal progress
dc.subjectVaccinium ashei
dc.subjectVaccinium corymbosum
dc.subjectYield
dc.titleEpidemiology of Septoria leaf spot on blueberry
dc.title.alternativetemporal dynamics, effect of leaf age, and relationship to defoliation and yield
dc.typeDissertation
dc.description.degreePhD
dc.description.departmentPlant Pathology
dc.description.majorPlant Pathology
dc.description.advisorHarald Scherm
dc.description.committeeHarald Scherm
dc.description.committeeKatherine Stevenson
dc.description.committeePhillip Brannen
dc.description.committeeAlbert Culbreath
dc.description.committeeScott Newmith


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