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Degree

Doctor of Philosophy, Ohio State University, Plant Pathology, 2005.

Abstract

Phomopsis cane and leaf spot is a disease of grape ( Vitis spp.) caused by Phomopsis viticola(Sacc.). The fungus survives winter in grape cane tissues that were infected in previous years. In the spring, conidia are splashed by rain onto new growth where they infect the plant tissues. The fungus can infect many parts of the grape, including shoots, rachises, leaves, and fruits, and infection typically takes place when the tissues are immature. The disease is considered to be monocyclic. The control of the disease has usually been done by either selective pruning of diseased canes (reducing inoculum) or preventative spraying of protectant fungicides onto new tissues. To extend our understanding of the epidemiology and control the disease, studies were conducted to: 1) evaluate a disease warning system by applying fungicides and fungicide-adjuvant combinations based on predicted infection periods utilizing measured weather conditions; 2) determine efficacy of a dormant fungicide spray program for controlling the disease in its early stage of development (spring); 3) correlate commercial control practices and environmental conditions with disease incidence based on a state-wide survey of commercial vineyards; and 4) determine spatial pattern of the disease in small (within a vine) and large (among vines) spatial scales using a range of spatial analyses. With the warning system, control was often equal to that obtained with a 7-day calendar-based protectant program, but with fewer fungicide applications. However, fungicides and fungicide-adjuvant combinations used with the warning system did not show curative activity in a controlled-environment study. A dormant fungicide application provided consistent, yet only moderate, control of the disease; however, growers who applied a dormant application or spring protectants tended to have less disease incidence based on the results of the commercial survey. Analyses of spatial patterns revealed that the disease tended to aggregate within a vine, but clustering of the disease among vines was not common. Based on the control achieved with the warning system, the moderate control by dormant applications, and management-practice information from the survey, early season application of protective fungicides was shown to be a key factor for successful management of P. viticola.

Subject Headings

Agriculture, Plant Pathology

Keywords

Plant disease management; Plant disease epidemiology; Grape; Vitis spp.; Vitis labrusca; Vitis vinifera; Phomopsis viticola; Plant disease warning system; Post-inoculation fungicide activity; Dormant fungicide application

Advisor

Laurence V Madden

Pages

181p.

Document number: osu1125542230
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=osu1125542230

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