Three labor-intensive control activities are currently used to reduce SWD-related yield losses: increasing the frequency of harvests, performing field sanitation, and implementing trapping programs to detect the presence of SWD populations. Further compounding these direct labor costs, the productivity of harvesting labor decreases as more frequent harvests and fruit losses due to SWD reduce the availability of marketable fruit to pick. Labor-intensive management activities are more intensely utilized by organic producers due to the lack of efficacious organic chemicals. Increasing the frequency of raspberry harvests means that fruit is harvested sooner, thus reducing the availability of ripe fruit in the field. SWD primarily targets red fruit that is fully ripened or overripe. While SWD also infest fruit before they ripen, this damage is less pervasive. Even if SWD infestations are present in less ripe fruit, the damage is less likely to be visible if the fruit is quickly harvested and cooled. Once fruit enters the cold chain, SWD development slows dramatically. As a result, a common practice among raspberry growers facing SWD damage has been to harvest a day sooner. Prior to the SWD invasion, raspberries were typically harvested every two to six days depending on the time of the season. Decreasing this interval to every one to five days implies a potential 20% to 100% increase in the frequency of harvests due to SWD, depending on the time of the season. Labor-intensive field sanitation efforts, which include pickers removing fallen and damaged fruit, nft growing system is another means of reducing the availability of fruit for SWD to infest. Removal of such unmarketable fruit from the field eliminates one potential source of SWD population growth, though external SWD populations can still be a significant source of damage.
Field sanitation is a recommended practice for all raspberry production even in the absence of SWD, but extensive field sanitation efforts are more likely to be observed with organic producers due to their greater damage rates and the costliness of such activities. Field sanitation is costly because pickers must be compensated. A common practice is to pay pickers a secondary, lower piece-rate for harvesting and disposing damaged fruit. Pickers performing field sanitation have been observed allocating as much as a quarter of their harvesting time to removing unmarketable fruit.26 For example, Rogers, Burkness, and Hutchison 34 examined SWD infestations in Minnesota raspberries and found that the average percentage of unmarketable fruit in untreated open plots was 29%. SWD infestations were found in 81% of sampled berries in these untreated open plots. Similarly, De Ros et al. 28 observed Italian berry growers allocating approximately a labor-hour per hectare each harvest day for sanitation efforts intended to control SWD. Growers who don’t remove fallen and damaged fruit have been observed to sustain increased damage rates as well as a higher probability of rejection of the whole shipment. A final labor-intensive management practice performed by many growers is the construction and maintenance of attractant-based traps. The materials required to produce these traps are inexpensive, but the construction and placement of the traps can be a labor-intensive activity. Growers utilize these traps to detect the presence of significant SWD populations in the fields they manage. However, available traps and attractants are nonspecific and capture many species of vinegar flies. In general, fly captures are a weak predictor of fruit losses. Producers often respond with more frequent insecticide applications and more intensive field sanitation when trap captures indicate the presence of large vinegar fly populations. Overall, the primary benefit of trapping programs has been to alert producers to the presence of SWD in areas where SWD had never been detected before. Regional trapping programs implemented by SWD researchers have also provided a rough measure of adult SWD activity at a given time of the year.
Sampling fruit directly provides a more accurate estimate of damage because virtually all fruit fly infestations in commercially viable California raspberries are SWD. However, direct sampling of fruit for infestations is time consuming for raspberry growers, who must transport their highly perishable product to a shipper within hours of a harvest. It is also a post facto measure since the fruit infestation measured has already occurred, so control at that time is of no value. In addition to growers implementing these labor-intensive SWD management practices, more frequent harvesting and fruit losses due to SWD limit how efficiently a grower can utilize labor. More frequent harvesting and fruit losses reduce fruit density in a field. Workers’ harvesting productivity is negatively impacted when they must spend additional time searching for marketable fruit that is less densely available. The harvest rate per raspberry picker can vary from one to five trays per hour depending on worker skill and fruit availability. An experienced picker can harvest up to 2.5 times more quickly than a novice, and yield alone can cause worker productivity to vary by a factor of two. SWD damage has the potential to reduce raspberry yields by up to 50% over a season and up to 100% in a specific harvest; therefore, it is clear that SWD damage can significantly affect workers’ productivity. Further compounding these labor-utilization issues, growers must offer a higher piecerate when productivity is low in order to retain their labor force and increased variability in available yield for harvest makes it more difficult for managers to allocate labor appropriately. The market for raspberry pickers is highly competitive. Workers who believe they can earn more money elsewhere, because less fruit is damaged, may leave during a harvest or not return for a subsequent harvest. The potential resulting labor shortage in fields with significant SWD damage could further exacerbate fruit losses due to SWD as unharvested fruit become overripe and act as a SWD breeding ground. Further, agricultural labor costs are also rising over time as the supply of labor from Mexico is shrinking due to improving economic conditions. It is difficult to observe these increased labor costs directly, but it is clear that they are not negligible. In 2015, a tray of 12 six ounce clam shells of conventional raspberries sold at an average price of $15.98 per tray based on Salinas-Watsonville and Oxnard district shipping point prices. According to a 2012 UC Davis study of raspberry production costs and returns, production costs were estimated to be $10 per tray of raspberries. Labor costs accounted for approximately half of these production costs, and the study did not report any SWD-targeting activities. The piece-rate alone averaged $4 per tray in a season. If one were to assume, conservatively, that these additional labor costs associated with managing SWD increased total labor costs by as little as 2% and 4% for conventional and organic raspberry producers, respectively, then these activities would account for a 1% and 2% increase in total production costs. Thus, a 1% increase is production costs would reduce a conventional raspberry grower’s profit margin by approximately 1.67%. If a similar cost structure is assumed for organic raspberry producers, then one would expect approximately a 3.34% reduction in profit margin resulting from the additional labor costs associated with managing SWD. Labor costs are assumed to increase by a greater percentage for organic producers because they are more reliant on labor-intensive SWD control methods.SWD’s invasion into North America has significantly harmed the California raspberry industry. We examined revenue losses and management costs associated with this invasive pest. Using a combination of field trial data and expert observations, nft hydroponic system we calculated that SWD has accounted for approximately $39.8 million in revenue losses, equivalent to 2.19% of realized revenues, for the California raspberry industry between 2009 and 2014. Conventional producers accounted for $36.4 million of these losses, equivalent to 2.07% of their realized revenues. Organic producers accounted for $3.43 million of these losses, equivalent to 5.74% of their realized revenues. SWD management activities have also significantly increased production costs for raspberry growers. We calculated that the cost of chemical purchases increased annual per hectare production costs for conventional and organic producers by $1,161.28 and $2,933.01, respectively. We also calculated that the cost of labor-intensive SWD management activities decreased conventional and organic raspberry producers’ profits by 1.67% and 3.34%, respectively.
Even though the industry has managed to adapt to the pest, these revenue losses and management costs have significantly reduced the profitability of the commercial production of fresh raspberries. Looking into the future, it is unclear whether SWD will remain a threat to California’s raspberry producers. On one hand, the primary biological reason that SWD has become such an economically damaging pest in both North America and Europe following its invasion is the absence of an effective natural enemy. In Asia, where SWD originates, the presence of effective natural enemies greatly reduces damages associated with the pest. Thus, the introduction of an effective biological control agent could dramatically reduce these estimated losses in the future. On the other hand, California’s raspberry producers rely heavily on chemical management options to reduce yield losses associated with SWD infestations. If SWD populations were to develop significant resistance to these chemicals over time or restrictions were placed on their use, then these estimated losses could increase dramatically. Agriculture is a key human activity in terms of food production, economic importance and impact on the global carbon cycle. As the human population heads toward 9 billion or beyond by 2050, there is an acute need to balance agricultural output with its impact on the environment, especially in terms of greenhouse gas production. An evolving set of tools, approaches and metrics are being employed under the term “climate smart agriculture” to help—from small and industrial scale growers to local and national policy setters—develop techniques at all levels and find solutions that strike that production-environment balance and promote various ecosystem services. California epitomizes the agriculture-climate challenge, as well as its opportunities. As the United States’ largest agricultural producing state agriculture also accounted for approximately 8% of California’s greenhouse gas emissions statewide for the period 2000–2013. At the same time, California is at the forefront of innovative approaches to CSA . Given the state’s Mediterranean climate, part of an integrated CSA strategy will likely include perennial crops, such as winegrapes, that have a high market value and store C long term in woody biomass. Economically, wine production and retail represents an important contribution to California’s economy, generating $61.5 billion in annual economic impact. In terms of land use, 230,000 ha in California are managed for wine production, with 4.2 million tons of winegrapes harvested annually with an approximate $3.2 billion farm gate value. This high level of production has come with some environmental costs, however, with degradation of native habitats, impacts to wildlife, and over abstraction of water resources. Although many economic and environmental impacts of wine production systems are actively being quantified, and while there is increasing scientific interest in the carbon footprint of vineyard management activities, efforts to quantify C capture and storage in annual and perennial biomass remain less well-examined. Studies from Mediterranean climates have focused mostly on C cycle processes in annual agroecosystems or natural systems. Related studies have investigated sources of GHGs, on-site energy balance, water use and potential impacts of climate change on productivity and the distribution of grape production. The perennial nature and extent of vineyard agroecosystems have brought increasing interest from growers and the public sector to reduce the GHG footprint associated with wine production. The ongoing development of carbon accounting protocols within the international wine industry reflects the increased attention that industry and consumers are putting on GHG emissions and offsets. In principle, an easy-to-use, wine industry specific, GHG protocol would measure the carbon footprints of winery and vineyard operations of all sizes. However, such footprint assessment protocols remain poorly parameterized, especially those requiring time-consuming empirical methods. Data collected from the field, such as vine biomass, cover crop biomass, and soil carbon storage capacity are difficult to obtain and remain sparse, and thus limit the further development of carbon accounting in the wine sector. Simple yet accurate methods are needed to allow vineyard managers to measure C stocks in situ and thereby better parameterize carbon accounting protocols. Not only would removing this data bottleneck encourage broader participation in such activities, it would also provide a reliable means to reward climate smart agriculture.