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. are the first studies to estimate the economic cost of SWD.
These studies utilize yield loss estimates and observations for strawberries, blueberries, raspberries plant container, 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. 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. 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. 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. The insecticide material and application costs are estimated to be $825.33 per hectare. However, these chemical applications may also provide incidental control of other pests. This implies that the estimate represents an upper bound of the potential chemical control costs associated with SWD.18 The revenue loss and management cost estimates in these prior studies can be substantially improved using current information about SWD-induced yield losses and management practices. Fruit losses due to SWD and SWD management costs have decreased over time as researchers and producers have developed and implemented better techniques for reducing crop losses. We can also more accurately estimate historic yield losses now that more is known about SWD biology, its spread, and the efficacy of different management techniques.Lastly, we can now incorporate increases in labor costs into these SWD management cost estimates.Prior estimates of SWD-induced revenue losses were based on the maximum observed yield losses in different industries where SWD infestations occurred. These estimates provide information about SWD’s damage potential, but do not yield an accurate estimate of actual SWD crop damage. Actual crop damage is useful for estimating revenue losses due to SWD and will differ by year and production style. This analysis incorporates field trial results and expert opinions to estimate SWD-induced revenue losses for the California raspberry industry. SWD infestations directly reduce raspberry yields in two ways. First, fruit infested by SWD decay more quickly. These yield losses are difficult to attribute to SWD because the initial infestation is difficult to detect, and the accelerated decay has a similar appearance to decay caused by fungal diseases, bacteria, and yeasts. Second, raspberry shippers that detect SWD infestations may reject the entire delivery from the grower.
Fresh fruit are held to rigorous quality standards. The risk of rejection of an entire delivery incentivizes growers to eliminate all visible defects in harvested fruit. SWD infestations are more prevalent late in the year as the population grows until winter weather reduces the population. Further, raspberry production is fairly concentrated geographically and the leftover, overripe fruit from nearby fields’ summer harvest acts as a breeding ground for SWD. SWD infestations are also more prevalent in fruit destined for the processing market, where the price is lower than in the fresh market. Fruit intended for processing are harvested later in the season, tend to be riper because they are harvested less frequently, and receive less frequent pesticide treatments. SWD damage rates could change significantly in the future due to pesticide resistance development and the introduction of new SWD management practices, including introducing biological control agents. Recent studies in the US and Europe found that indigenous parasitoids had limited effect on SWD populations. However, in Asia, where SWD originates, several endemic parasitoids attack and develop from SWD. We begin by examining SWD-induced yield losses in California’s conventional raspberry industry. The original reports of SWD damage in the raspberry industry indicated that as much as 50% of production could be lost if SWD was left unmanaged. Yield losses of this magnitude occurred as raspberry producers first learned how to manage SWD, but are now uncommon due to implementation of extensive academic research and industry experience. According to private communications with conventional raspberry producers, they have managed to reduce SWD induced yield losses to less than 3% of production. In recently published reports, conventional raspberry producers that employ effective chemical management programs face virtually no yield losses due to SWD. This substantial reduction in yield losses is primarily attributable to two factors. First, conventional raspberry producers have access to cheap and effective chemical management options. Second, these producers are harvesting their crop more frequently in order to reduce the amount of time raspberries are susceptible to infestation. These observations of actual SWD-induced yield losses are consistent with field trial observations as well. Entomologists Kelly Hamby and Frank Zalom monitored traps and evaluated fruit samples for damage between October 2010 and December 2012 in both organically- and conventionally-managed raspberry sites. Analyzing the 40-fruit samples collected from these fields resulted in estimated yield loss observations for raspberry producers employing standard management practices at the time. SWD-induced yield losses for conventional producers in the study were estimated to be approximately 10% of production in 2011 and less than 1% in 2012. These estimated yield losses are consistent with those observed by De Ros et al. in Italy between 2011 and 2013. De Ros et al. estimated container raspberry losses of 11.5% prior to i and 3.24% after the implementation of an integrated strategy. The yield losses observed in the UC Davis study were concentrated in the fall harvest. The summer harvest is hypothesized to experience less SWD pressure because the population grows throughout the year until cold weather arrives and lack of host fruit in the winter significantly reduces population levels. 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, and that losses after 2011 correspond to the yield losses observed in 2012. Raspberry production and price data are obtained from the U.S. 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.