SWD biology and infestation intensity is affected by climatic conditions and the availability of host fruit, implying that different climatic conditions and influences of neighboring crops could significantly impact SWD-related yield losses.On the other hand, organic raspberry producers still face significant SWD-induced yield losses. Private communications with raspberry producers indicate that these producers experience yield losses between 5% and 15% of production due to a lack of efficacious chemical treatments approved for organic use, and the efficacy and high cost of other labor-intensive SWD management practices. Once again, these field observations are consistent with the yield losses measured in field trials. SWD-induced yield losses for organic raspberry producers in the study were estimated to be approximately 12% of production in both 2011 and 2012. We calculate yearly estimates of industry-level revenue losses using these observed yield losses due to SWD and a procedure similar to Goodhue et al. . First, we assume an ownprice elasticity of demand for raspberries of -1.66. This elasticity value is the value estimated for fresh raspberries by Sobekova, Thomsen, and Ahrendsen .Second, we assume that actual yield losses in the California raspberry industry correspond to the yield losses observed in the field trials. Specifically, we assume that SWD-induced yield losses between 2009 and 2011 correspond to the yield losses observed in 2011,big plastic pots and that losses after 2011 correspond to the yield losses observed in 2012.

Census of Agriculture and various National Agricultural Statistics Service surveys.Table 2 provides the resulting revenue loss estimates organized by production practice and year grouping. California’s conventional raspberry producers faced a total of $36.1 million in revenue losses due to SWD between 2009 and 2011. These estimated revenue losses are equivalent to 4.62% of realized revenues over the same period. After 2011, effective SWD management techniques in conventional production eliminated virtually all revenue losses. Revenue losses due to SWD between 2011 and 2014 are estimated to be $277 thousand, which is less than 1% of realized revenues over the same period. In total, California’s conventional raspberry producers faced $36.4 million in revenue losses due to SWD between 2009 and 2014. California’s organic raspberry producers faced a total of $3.43 million in revenue losses due to SWD between 2009 and 2014. These estimated revenue losses are equivalent to 5.74% of realized revenues over the same period. Revenue losses of this magnitude are expected to continue in organic raspberry production until more effective chemical, cultural, or biological management programs are discovered. Furthermore, revenue losses incurred by organic raspberry producers could potentially increase dramatically if SWD populations develop greater resistance to the current, limited set of chemical controls approved for organic use.SWD management is multifaceted. In addition to yield losses, managing SWD has significantly increased production costs for raspberry producers. Raspberry growers increase the number of insecticide applications and use additional labor to harvest their crop in response to SWD infestation pressure. These necessary insecticide applications require additional chemical purchases and access to sprayers and specialized equipment through custom application or purchase.

Overuse of pesticides can lead to rejections of shipments if residues exceed legal tolerances for the chemicals; however, producers who adhere to mandatory label rates should, theoretically, never encounter this problem. Conventional raspberry producers have access to a variety of insecticides that provide excellent control for SWD populations at present. Raspberry growers observed in the UC Davis study discussed earlier applied SWD-targeting insecticides four to six times for both the fall and spring harvests. The most commonly used insecticides for this purpose were spinetoram, zetacypermethrin, and malathion. Assuming these chemicals are applied at their maximum label rates and with generic purchase prices observed in 2015, the per hectare material costs of these insecticide applications are $179.40, $7.22, and $29.78, respectively. Using a conventional raspberry grower observed in the UC Davis study as a point of reference, an example chemical management program included two applications of spinetoram and a combined application of zeta-cypermethrin and malathion in both the fall and spring harvest seasons. Each application is estimated to have labor and equipment costs of $61.78 per hectare.In 2015, such a program would cost an estimated $581.14 per hectare in both the fall and spring harvests for a total cost of $1,161.28 per hectare for a single planting. This is consistent with the per hectare treatment program cost of $825.33 observed in Goodhue et al in 2011. Even though conventional raspberry producers have developed effective chemical management programs that virtually eliminate fruit losses due to SWD, organic producers still experience non-trivial yield losses due to more expensive and less effective insecticide options.Most California organic raspberry producers used only two SWD-targeting insecticides, spinosad and pyrethrin, during the time of this study. Of these two insecticides, only the organic formulation of spinosad has efficacy comparable to conventional insecticides.Spinosad applications are more expensive than conventional insecticides and organic growers are limited by its labeled use of two consecutive applications followed by rotation to a product containing another class of insecticide for resistance management.

Pyrethrin has been shown to have a limited effect on SWD populations. It is typically applied in conjunction with spinosad or other organic insecticides because it does not provide sufficient control on its own. Assuming spinosad and pyrethrin are applied at their maximum label rates and with generic purchase prices observed in 2015, the per-hectare material costs of these insecticide applications are $200.60 and $119.13, respectively. In the UC Davis study, organic raspberry growers were observed applying these insecticides between five to nine times for each seasonal raspberry harvest. Using an organic raspberry grower observed in the UC Davis study as a point of reference, a typical chemical management program included five applications of pyrethrin in the fall, three of which were applied in conjunction with spinosad, and six applications of pyrethrin in the spring, two of which were applied in conjunction with spinosad. Assuming the stated per-hectare material, labor, and equipment costs, such a program would cost an estimated $1,506.35 per hectare in the fall and $1,486.66 per hectare in the spring for a total cost of $2,933.01 per hectare for a single planting. It is important to note that even as these insecticide applications reduce SWD populations, they also provide control for other pests such as the light-brown apple moth, Epiphyas postvittana. As a result, it is difficult to attribute the entire cost of these chemical management programs strictly to the management of SWD. However, few insecticide sprays were applied to California raspberries before the SWD invasion, and the light-brown apple moth, another invasive insect, only impacts portions of the Santa Cruz and Monterey County raspberry production areas at present. The light-brown apple moth can also be effectively controlled more inexpensively with the organic microbial insecticide Bacillus thuringiensis Berliner. Therefore, we can infer that the majority of the observed insecticide applications included in this analysis were intended to control SWD populations.We also consider the additional labor costs associated with managing SWD in order to develop a comprehensive estimate of SWD management costs. Like many other horticultural products,growing berries in containers raspberries are extremely labor-intensive to produce. Labor, the primary production cost, includes planting, pruning, weeding, spraying, hauling, cleanup, field sanitation, and harvesting.13 SWD control programs necessitate labor-intensive management practices inaddition to chemical applications. 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.27 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.26 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, is another means of reducing the availability of fruit for SWD to infest. Fallen and damaged fruit are a breeding ground for SWD and other Drosophila species alike. 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.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. 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.6 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.