For complex canopies like grapevines, the results highlighted the need to use a 3D radiation model because these models can represent the vertical and horizontal variability in the canopy and their effect on light interception accurately. Chapter 3 developed and validated a three-dimensional model for grape berry temperature to understand whether the effect of excess sunlight on grape production can be mitigated by designing and managing vineyards in a way that effectively creates a favorable berry microcli-mate. For the first time, a 3D vine-resolving structural model was coupled with a high-resolution energy balance model for providing accurate and spatially-explicit predictions of berry temperature dynamics. The developed 3D model accurately simulated the spatial and temporal temperature fluctuations of grape berries in vineyards with different climate, topographies, and trellises. Chapter 4 explored different scenarios to mitigate the effect of excess sunlight and temperature. Previously developed models for grape temperature have not been used to evaluate the interacting effects of different management strategies to reduce grape berry temperature. This chapter measured the effect of vineyard design and shade cloth on berry temperature and quantified trade-offs between the different management strategies to maintain optimal berry heat balance and reduce the elevated berry temperatures.

Altering light interception by using shade cloths affected the reduction of elevated berry temperatures depending on the vineyard design. A great effect of the shade cloths was found in clusters exposed to direct sunlight for prolonged hours, plastic round plant pots which tended to be in cases where the vines had greater plant spacing relative to plant height, and where rows were oriented NS and NW-SE in either a flat or sloped terrain facing W or SW, respectively. While changing the row orientation to NE-SW can be an effective long-term practice to reduce the effect of elevated temperature, for cases where changing the vineyard design is not possible, the shade cloths presented an alternative to reduce unfavorable berry temperatures in many cases. The variables that determine cluster exposure to direct sunlight, such as topography, trellis systems, row orientation, and shade cloths should be considered carefully to develop management strategies for optimizing grape quality. The primary novel outcome of this dissertation that advances the current state-of-the-art is the development of a new tool that could be used to address the role of agricultural management in climate adaptation. Technologies that increase the rate of adaptation to climate change are of great value to farmers, the wine industry, policymakers, and the scientific community. In future studies, the 3D model could be used to evaluate the effect of vineyard designs on berry temperature under changing environmental conditions, to assess the effect of different irrigation strategies on grape production, and to relate the spatial and temporal variability in berry temperature to variations in berry quality traits.

Drosophila suzukii , also known as the spotted wing drosophila , is a vinegar fly originating from Southeast Asia. SWD was first detected in North America in August 2008 in Santa Cruz County, California, where it was observed infesting strawberries and caneberries.In 2009, SWD was detected in Washington, Oregon, and Florida. By 2010, SWD was detected in Utah, Mississippi, North Carolina, South Carolina, Wisconsin, and Michigan in the United States, and Alberta, Manitoba, Ontario, and Quebec in Canada.3 Recent trapping indicates that SWD can be found in virtually any region of North America where host fruit are available. A coincidental invasion of SWD with a genetically distinct population has also been observed in Europe, with initial detections in both Spain and Italy in 2008, followed by its spread throughout the continent. In North America, SWD is primarily a pest of berries and cherries. In Europe, it is reported to also damage a number of stone fruits and grapes. Unlike native vinegar flies in North America and Europe, female SWD possess a serrated ovipositor that can pierce the skin of healthy, soft-skinned fruits to lay eggs. These eggs quickly develop into larvae, which consume the fruit and render it unmarketable. The only other Drosophila species known to oviposit in sound, marketable fruit is Drosophila pulchrella Tan. This species is native to Japan.1 Growers have attempted to mitigate crop damage risk by applying additional insecticide, harvesting more frequently, performing field sanitation, and implementing trapping programs to detect SWD populations. These management practices are costly and many growers still face significant yield losses from SWD infestations. We examine the economic impact of SWD infestations in the California raspberry industry.

Raspberry producers are perhaps the most affected by SWD’s invasion among California commodities, although producers of blueberries and cherries have experienced substantial losses too. Strawberry producers have experienced lower damage rates and primarily on the lower-value fruit produced for processing. SWD-related losses in these industries vary by year and crop depending on management practices, weather conditions, time of the year, and geographic location. A primary motivation for focusing on the California raspberry industry is that California accounts for the majority of raspberry production in the U.S. and the raspberry industry accounts for the majority of economic losses due to SWD among berry crops. 6 A second motivation is the magnitude of change in pest management practices; few of the SWD control practices used by raspberry producers were needed to prevent injury from other pests prior to its establishment. Economic losses in the California raspberry industry include the cost of managing SWD and the value of the fruit lost due to SWD infestations despite management efforts. First, we compute the cost of the chemical management programs and the labor-intensive sanitation practices implemented to mitigate SWD-related yield losses. Second, we calculate the industry level yield losses due to infestation. These components form an estimate of the full economic cost of SWD’s invasion into California raspberry production.Raspberry production is a valuable component of California’s agricultural industry. In 2013, raspberries were estimated to be the twenty-seventh largest crop in California by value of production. California accounted for 74% of all raspberry production in the United States. The United States is the third largest producer of raspberries in the world, producing 91,300 tonnes, after the Russian Federation and Poland, which produce 143,000 and 121,040 tonnes, respectively. Across all counties, California’s raspberry production was worth an estimated $239 million according to the United States Department of Agriculture’s National Agricultural Statistics Service , nft hydroponic and $437 million according to California County Agricultural Commissioners’ Reports. The difference in these estimates reflects that the NASS data report cash receipts to producers while the Agricultural Commissioners’ Reports estimate the total value of production. Figures 1, 2, 3, and 4 plot California raspberry hectares, production, yield per hectare, price per kilogram, and the total cash receipts between 2004 and 2013. Note that raspberry hectares multiplied by yield per hectare is equivalent to production, and production multiplied by price per kilogram is equivalent to total cash receipts. Four counties account for virtually all commercial raspberry production in California: Ventura, Santa Cruz, Santa Barbara, and Monterey. In 2014, Ventura County produced approximately 52% of California’s raspberry crop by value, $241 million, on 1,873 hectares. Raspberries are the third most valuable crop in Ventura County. Santa Cruz County produced approximately 28% of California’s raspberry crop by value, $131 million, on 979 hectares. Raspberries are the second most valuable crop in Santa Cruz County. Santa Barbara County produced approximately 10% of California’s raspberry crop by value, $45.2 million, on 591 hectares. Raspberries are the ninth most valuable crop in Santa Barbara County. Monterey County produced approximately 10% of California’s raspberry crop by value, $45 million, on 316 hectares. Raspberries are the sixteenth most valuable crop in Monterey County. Table 1 summarizes California raspberry production by county. Counties are listed from north to south along the Pacific Coast. Figure 5 identifies these berry-producing regions with a stylized map of California.The crop is planted in the winter and then harvested twice, first in the fall following planting and then in the subsequent summer.

Both harvest seasons last approximately three months, with crews harvesting fruit every three days on average. Variations in harvest frequency depend on yields and pest management activities. Yields are low at the beginning and end of a harvest season, and peak near the middle of a season. Pesticide applications may require an interval of time, depending on the particular pesticide, before normal harvesting activities can resume. This period is known as the pre-harvest interval , and it is determined by the U.S. Environmental Protection Agency. Occasionally, low yields are realized during the harvest season due to crop damage resulting from weather, pest activity, or other external factors. The summer harvest is typically larger than the fall harvest. Organically produced raspberries represent a significant share of total California raspberry production. In 2008 and 2011, California’s organic raspberry production was valued at $11.4 million and $8.98 million, respectively, according to the USDA-NASS. In 2012, 408 hectares of California raspberries were organically managed according to the University of California Agricultural Issues Center. Raspberry prices vary throughout the year, but on average organic raspberries are sold at a price premium. In 2015, the national average retail price of organic raspberries over the entire year was $3.52 per six ounce tray according to the USDA Agricultural Marketing Service. The average retail price of conventional raspberries over the same period was $2.55 per tray. The average California terminal market prices for organic and conventional raspberries were $3.29 and $1.97 per tray, respectively. California raspberries are a major export crop. In 2013, the combined category of raspberry, blackberry, mulberry, and loganberry exports was the twentieth largest export crop category by value in California. Raspberries account for the majority of the production volume and the total value of this category. This California export category was valued at $157 million, and accounted for approximately 85% of total US fresh and processed raspberry, blackberry, mulberry, and loganberry exports. 84% of these exports are received by Canada, 6% by Japan, and 5% by the European Union. The presence of SWD has clearly increased production costs and caused yield losses for California raspberry producers through a variety of channels. Three previous studies have attempted to quantify the economic cost of the SWD invasion. However, these studies occurred within one or two years of the first SWD infestations in North America when information on the pest was still sparse and management techniques were rapidly evolving. We can improve on these original estimates now that much more is known about SWD biology, risks, and management. We briefly review these original studies before establishing new estimates of the economic cost of SWD in the California raspberry industry. Walsh et al. 1 and Bolda et al. 6 are the first studies to estimate the economic cost of SWD. These studies utilize yield loss estimates and observations for strawberries, blueberries, raspberries, blackberries, and cherries in California, Oregon, and Washington in conjunction with production data to calculate revenue loss estimates for each state and crop pairing. Walsh et al.1 assume a yield loss of 20% for all the listed crops in these states. As a result, the study estimates a total of $511 million in potential damages annually due to SWD. Bolda et al.6 continue the analysis by assuming the maximum reported yield losses of 40% for blueberries, 50% for blackberries and raspberries, 33% for cherries, and 20% for processing strawberries. The study concludes that potential revenue losses across these states and crops could be as large as $421.5 million given current prices.6 Goodhue et al. 18 refine these estimates of lost revenue for the California raspberry and strawberry industries by including potential price responses into their estimates. This additional assumption reflects that as the production of raspberries and strawberries decreases, the prices of these products may increase in response. The interaction between production and price is quantified with the inverse own-price elasticity of demand for each crop. The elasticity predicts the percentage change in price of a good in response to a 1% increase in quantity demanded. Drawing upon elasticity estimates established in prior studies, the authors conclude that SWD-induced yield losses could decrease California raspberry and processed strawberry revenues by up to 37% and 20%, respectively. The authors also evaluate the cost of different SWD-targeting insecticide applications and the cost of a specific conventional raspberry pest control program in California’s Central Coast region.