"Potato production systems have been long plagued by soilborne diseases which can compromise tuber quality and yield. Verticillium wilt caused, by Verticillium dahliae Kleb., is a widespread disease of potatoes (Solanum tuberosum L.) and is an annual problem for potato growers throughout the USA. When not-treated, severely infested fields can lose marketable yield from 30-50%. The cost of pre-plant fumigation, new restrictions imposed by government agencies on the application of soil fumigants, and demand for high quality tubers has led to a renewed focus on management of Verticillium wilt in potato production in Michigan and across the USA. Experimental field trials were conducted to determine efficacy of several commercially available fungicides applied in-furrow at-planting to decrease V. dahliae propagules in the rhizosphere and wilt disease in plant stems. Additional trials were conducted based on preliminary results to determine the effects of fluopyram at three application times; at-planting, at-emergence, and at-tuber initiation, for management of Verticillium wilt. At-emergence application of fluopyram or any combination of application times coupled with an at-emergence application led to a reduction in V. dahliae propagules in stem sap and subsequent yield increase, but had no effect on V. dahliae propagule levels in the rhizosphere. Finally, the effects of seven different at-planting and/or foliar treatment programs for control of Verticillium wilt were evaluated with special attention to root-lesion nematode (RLN) levels in the soil. Significantly lower levels of Verticillium wilt symptoms at the end of the growing season were seen in treatments when compared to the non-treated control, however, no significant difference was observed in tuber yield, V. dahliae propagule levels in the soil, or RLN populations in the soil. In addition to the work on Verticillium wilt, an approach integrating traditional soil sampling and GIS mapping systems was developed to analyze edaphic qualities and quantify soil microbial diversity across entire fields in order to examine correlations between yield and soil biological factors on a spatial scale. The automated geostatistical interpolation of soil properties has greatly reduced the cost and time of the statistical methods utilized in predictive statistics. The incorporation of inoculum levels along with the use of geostatistical analysis led to a methodology of sub-field management strategies based on conditional probability and binary mapping to predict where Verticillium wilt may occur based on pathogen populations and disease thresholds. Sub-field management strategies allow for more accurate management of problem areas in fields with fewer inputs. The methods presented are a novel approach to analyzing and predicting potato crop health, soil abiotic factors, and soilborne pathogens throughout an entire field with low error. Incorporation of these methods into potato integrated disease management may reduce management costs while simultaneously reducing the environmental impact of management inputs and increasing profitability."--Pages ii-iii.
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