Essays on the Economics of Powdery Mildew in the California Grape Industry.

다국어 초록 (Multilingual Abstract)

This dissertation develops a detailed analysis of the pesticide application decisions made by grape growers in California to manage powdery mildew in their vineyard. The broader context for this research is the use of forecasting tools to mitigate agricultural production risk due to pests and disease, and the main question is how the behavioral biases of the growers affect their use of information about the risk of a specific disease outbreak.
Grape powdery mildew is a fungal disease that affects grape crops all over the world and is the most significant disease in terms of expenses for control and losses in quality and yield faced by grape growers in California. Powdery mildew management accounts for the majority of total pesticide applications by California grape growers, and the pecuniary costs of managing powdery mildew are in the range of 3--7 percent of the gross value of production in places where powdery mildew pressure is significant. The total pecuniary costs of managing powdery mildew in California in 2011 are estimated in this dissertation to be about $189 million.
This dissertation examines changes in the management of powdery mildew by grape growers with the use of the Gubler-Thomas Powdery Mildew Index (PMI), a forecasting model designed to guide the applications of pesticides used to manage powdery mildew in vineyards. The analysis is done with the use of a structural dynamic model, a reduced-form econometric estimation, and a comparative study of changes in the costs of managing powdery mildew with the use of production budgets for a sample of representative growers.
Chapters 1 and 2 provide introduction, background and estimates of pecuniary and non-pecuniary costs of managing powdery mildew in California. Chapter 3 develops a structural dynamic model and estimates the parameters of the function of the expected loss of crop value from an outbreak of powdery mildew. The parameter estimates are then used to evaluate the changes in the welfare of grape growers with the use of the PMI. The results suggest that average level of welfare declines or doesn't change for growers of wine grapes with the use of the PMI. At the same time, average welfare increases for growers of raisin grapes in all counties. Chapter 4 explores the effect of an online training course on the management of powdery mildew by the growers and the resulting changes to the costs and the environmental impact of pesticide applications. The analysis suggests that the costs of managing powdery mildew increase for most growers by between $14 to $84 per acre. These costs are likely to be offset by the private benefits the growers receive. At the same time, the environmental impact of the changes in powdery mildew management is negative, and it is unclear whether private benefits offset these public costs. Chapter 5 examines the economic value of an automated powdery mildew sprayer, which requires little decision-making input from the growers. The results suggests that growers would not benefit from the automated sprayer in the areas where the labor costs are high, unless the sprayer was designed to reduce the amount of labor used to drive the sprayer through the vineyard. At the same time, growers in areas with low costs of labor and a shorter season of powdery mildew management would benefit from an automated sprayer, saving about 1--2 percent of total production costs.
This dissertation contributes to a better economic understanding of powdery mildew on grapes and the powdery mildew management programs employed by grape growers in California. It shows that powdery mildew treatment strategies used by growers in California vary widely among the growers of different categories of grapes and among different regions of the state, and explains the factors behind some of the variation. In addition, analysis in this chapter provides a starting point for discussing the economic benefits of using robots to optimize management of grape crops. Techniques developed in this dissertation can be used to address related problems, such as other diseases of grapes or other perennial crops.