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Case Study 2: Plant Quarantines and Hass Avocados

ROLE OF SCIENCE IN SOLVING PEST QUARANTINE PROBLEMS: HASS AVOCADO CASE STUDY

WALTHER ENKERLIN HOEFLICH

Dirección General de Sanidad Vegetal, Secretaría de Agricultura, Ganadería y Desarrollo Rural, México

Free trade among nations and regions is the driving force behind the relatively new and more widely accepted pest quarantine concept. In general, the quarantine concept for economically important pests has evolved from a near-zero threshold or near-zero pest tolerance, including the very stringent quarantine concept known as "absolute quarantine" to a more flexible approach in which a threshold above zero is allowed. This approach focuses more on integrating, in a system, a number of control measures in orchards, packing facilities, and transport to prevent pest establishment in pest-free countries or regions. This concept is known as a systems approach.

This modern approach facilitates trade by being less restrictive and at the same time providing quarantine security for the importing country. It is a more scientific approach that requires a comprehensive understanding of the pest biology and ecology as well as a larger and more solid infrastructure for the systems approach implementation. The Hass avocado case provides a good example on how science can be used to solve an old quarantine problem between two countries.



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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference 9 Case Study 2: Plant Quarantines and Hass Avocados ROLE OF SCIENCE IN SOLVING PEST QUARANTINE PROBLEMS: HASS AVOCADO CASE STUDY WALTHER ENKERLIN HOEFLICH Dirección General de Sanidad Vegetal, Secretaría de Agricultura, Ganadería y Desarrollo Rural, México Free trade among nations and regions is the driving force behind the relatively new and more widely accepted pest quarantine concept. In general, the quarantine concept for economically important pests has evolved from a near-zero threshold or near-zero pest tolerance, including the very stringent quarantine concept known as "absolute quarantine" to a more flexible approach in which a threshold above zero is allowed. This approach focuses more on integrating, in a system, a number of control measures in orchards, packing facilities, and transport to prevent pest establishment in pest-free countries or regions. This concept is known as a systems approach. This modern approach facilitates trade by being less restrictive and at the same time providing quarantine security for the importing country. It is a more scientific approach that requires a comprehensive understanding of the pest biology and ecology as well as a larger and more solid infrastructure for the systems approach implementation. The Hass avocado case provides a good example on how science can be used to solve an old quarantine problem between two countries.

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference The state of Michoacan in the South Pacific coast of Mexico is a large producer of avocados. Michoacan grows around 100,000 ha of Hass avocados producing around 800,000 tons of fruit per year (Paz Vega, 1989). About 93 percent of the production is sold domestically and 7 percent is sold abroad. For the past 10 years the main importers of Mexican Hass avocados have been Japan, France, England, Switzerland, and Canada. The United States has been importing increasing amounts since 1997. For over 80 years Mexico had been trying to export Hass avocados to the United States. However, exports were prohibited due to a quarantine restriction against three fruit fly species and two avocado fruit borers. The approval and enforcement of the North American Free Trade Agreement in 1991 provided space for negotiations and an opportunity for science to take part in the decision-making process (Figure 9-1). The following section describes the experimental procedures used to solve this quarantine problem. METHODOLOGY For over 80 years the U.S. Department of Agriculture (USDA) had imposed a quarantine restriction on the Mexican Hass avocados, which are considered to be a host of the Mexican fruit fly (Anastrepha ludens , Loew), the sapote fruit fly (A. serpentina, Wied.), and the guava fruit fly (A. striata, Schiner), as well as a host of two species of avocado fruit borers. Although it is known that some species of fruit flies infest certain avocado varieties (e.g., Sharwil avocado is considered to be a poor host of the Oriental fruit fly [Bractocera dorsalis] in Hawaii [Oi and Mau, 1989]), there is no scientific evidence of Hass avocado infestations by any fruit fly of the genus Anastrepha. In the case of the fruit borers it has been well documented that the Hass avocado is a primary host of this insect pest. However, scientific evidence also shows that fruit borers are temperature sensitive and their geographical distribution is restricted to certain altitudes within the avocado growing region in Michoacan. The avocado producing region in Michoacan is located at an altitude of 1400-2100 m above sea level and it is considered to have a temperate climate (Paz Vega, 1989). During the fall and winter months (October to February), the minimum and maximum temperatures fluctuate from 0 to 10 °C and from 16 to 20 °C, respectively. A research project was conducted in Michoacan to assess the susceptibility of Hass avocados to the three above-mentioned fruit fly species and to determine the geographical distribution of the avocado fruit borers. Considering that the quarantine problem implicated two countries, the exporter (Mexico) and the importer (United States), the research was approached in a binational fashion. The Mexican and U.S. governments decided to integrate a binational research team with fruit fly and quarantine specialists from both countries. The Mexican group Secretaria de Agricultura, Ganaderia y Desarrollo Rural, Direccion General de Sanidad Vegetal (SAGAR/DGSV) prepared a preliminary research protocol that was then sent to the USDA group

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference of Animal and Plant Health Inspection Service/Agricultural Research Service (APHIS/ARS) for review. Once the research protocol was ready, a 10-month laboratory and field research program began in Michoacan. Periodical site visits were conducted by the USDA group for review and advice on the experiment. The research project was split into two main experiments and two side experiments as follows (see Figure 9-1). The main experiments were to determine the susceptibility of Hass avocados to Anastrepha spp. under forced laboratory conditions, and the susceptibility of Hass avocado to Anastrepha spp. under forced field conditions. The side experiments were to assess the Anastrepha spp. adult population fluctuation in the Hass avocado growing region, and the Hass avocado Anastrepha spp. natural field infestations. For the laboratory and field susceptibility experiments, a range of physiological stages of avocado fruits were exposed to Anastrepha spp. forced infestations. The parameter used to measure the physiological stage of the fruits was percent dry matter (Enkerlin et al., 1994). The percent dry matter values used were 15, 17, 20, 22, 24, 26, 28, 30, 32, 34, and 35. Fruits containing less than 21 percent dry matter are considered to be unripe and with 21 percent or more are considered physiologically mature and ready for harvest. For each percent dry matter, 40 avocado fruits were exposed immediately after harvest to forced infestations. Also, for each percent dry matter, fruits were exposed to forced infestations in the field while still attached to the tree and to laboratory forced infestations 3, 24, 48, 72, 96, and 120 hours after harvest. For the laboratory forced infestations, 50 sexually mature fruit fly couples were placed in 50-cm3 cages. For the field experiments the same amount of couples were placed in 1-m3 cages. In the laboratory, environmental conditions (temperature and relative humidity) were controlled to avoid detrimental effects on the fruit fly colonies used for the infestations. For the laboratory experiments, 10 fruits were placed per cage and were exposed for 24–48 hours to males and gravid females. For the field experiments fruits were exposed for 96 hours. After the infestation period, fruits were taken out of the cages and placed in plastic trays containing a 3-cm layer of vermiculite. Fruit was held for 18–25 days to allow for larvae development and pupation. After this time period fruits were dissected and vermiculite sieved to collect third instar larvae and pupae. The pupal stage was used as the critical developmental stage to assess Hass avocado fruit fly host status. The number of larvae and pupae was quantified and percent pupation and adult eclosion were calculated. The number of pupae per fruit was estimated to assess the severity of the infestations (Enkerlin et al., 1994). Orange (Citrus sinensis), sapote (Calocarpum sapota), and guava (Psidium guava), which are the primary hosts of the fruit flies utilized in the experiment, were used as controls. For each of the avocado percent dry matter evaluated, 120 fruits of each primary host were exposed to fruit fly infestations. To compare the level of infestations of the fruit flies in their natural hosts against the avocado infestations and to be able to monitor the quality of the fruit fly colonies used in the experiment, the level of infestation (pupae/fruit) and

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference FIGURE 9-1. Case Study: Hass Avocado Background Chart. Binational research to assess the susceptibility of Hass avocados to pest infestation.

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference percent pupation of the three fruit fly species in their natural hosts was measured (Enkerlin et al., 1994). The levels of infestation (pupae/fruit) obtained for each percent dry matter were statistically analyzed using an analysis of variance (P = 0.05) and a Tuckey studentized range test (SAS Institute, 1988). To determine the presence and abundance of the three fruit fly species under study, an extensive network of McPhail traps was deployed and operated from July 1993 to April 1994 in the avocado growing region of Michoacan. A trap density ranging from one trap for every 1–5 ha was used. These trap levels meet with the protocol requirements recommended for certification programs in Mexico and the United States. Traps were serviced weekly and fly captures recorded. To obtain a measure of the fruit fly population levels, data were transformed to the population index, fly per trap per day (FTD). Also during the same time period, to assess natural fruit fly infestations, a systematic fruit sampling was conducted in the orchards where traps had been placed (Enkerlin et al., 1994). RESULTS AND DISCUSSION Forced Infestations Under laboratory and field forced infestations, Hass avocados were shown to be a good host of A. ludens. Healthy A. ludens pupae were recovered from all the Hass avocado physiological stages that were evaluated. Hass avocados were a poor host at 15 and 17 percent dry matter. However, once the fruits approached physiological maturity (21 percent dry matter), they became highly susceptible (Figure 9-2, Table 9-1). For A serpentina, the Hass avocado becomes susceptible at 20 percent dry matter. Infestation levels for this species were lower but can still be considered a susceptible host especially at 20 and 22 percent dry matter. For A striata, a very low infestation was obtained at 22, 24, and 26 percent dry matter. Hass avocados are considered to be a very poor host of this fruit fly species (Figure 9-2, Table 9-1). The infestation drop observed at 24 percent dry matter is related to the fall and winter temperatures and photoperiod, not to an effect of the dry matter content on the development of immature stages of the insect. Once the temperature starts to rise and days become longer, infestation levels start to increase (Figure 9-2, Table 9-1) (Enkerlin et al., 1994). In relation to the infestation on fruits that were attached to the tree and on those infested at different time intervals after harvest, results show, in general, an increase in susceptibility for each increase in time after harvest (Table 9-2). It is important to note that while the fruit was attached to the tree, at any physiological stage (percent of dry matter), no infestation was recorded. Twenty fruits were dissected to determine if female fruit flies had actually laid eggs under the skin of the fruit. Forty-eight egg masses (ca. 839 eggs) were found submerged in the fruit flesh with no signs of eclosion. Hard tissue surrounding

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference FIGURE 9-2. A. ludens, A. serpentina, and A. striata Forced Laboratory Infestation of Hass Avocado (Uruapan, Michoacan, 1993–1994) Table 9-1. Statistical Analysis of Hass Avocado Fruit Fly Infestation Levels in Relation to Percentage of Dry Matter (Uruapan, Michoacan, 1993–1994) Dry Mattera (%) A. ludens Pupae/Fruit (avg.) Statistical Differenceb (P = 0.05) A. serpentina Pupae/Fruit (avg.) Statistical Differenceb (P = 0.05) 15.20 0.02 B 0.00 B 17.20 0.10 B 0.00 B 20.20 26.00 A 1.70 A 21.50 24.00 A 1.20 AB 23.90 1.60 B 0.30 AB 26.40 0.50 B 0.00 B 29.50 0.30 B 0.03 B 30.80 0.20 B 0.05 B 32.30 0.64 B 0.10 B 33.40 0.57 B 0.08 B 35.00 7.46 B 0.15 B a Parameter used in the experiment as an indicator of physiological maturity of avocado fruits: the higher percent dry matter, the more mature the fruit. (Alternatively, avocado oil content could be used as indicator of maturity.) b The analysis of variance shows if there is statistical differences in infestation levels among percent dry matter values. Figures with the same letters are statistically equal. P = 0.05, Tuckey studentized range test (SAS Institute, 1998).

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference the egg masses in the form of callus was found (Enkerlin et al., 1994). This was also observed by Smith (1973), Sarooshi et al. (1979), and Armstrong et al. (1983) in previous experiments with other avocado varieties. These authors report this event to be a resistance factor of the avocado fruit associated to other unknown biological factors (Table 9-2). Natural Infestations Results from the 10-month trapping in the avocado region showed that, during this trapping period, only the Mexican fruit fly (A. ludens ) was present in the region at detectable levels. The other two species (A. serpentina and A. striata) were not detected during the 10 months of trapping. A. ludens was captured throughout the trapping period except for January when the lowest temperatures were recorded in the region. A. ludens populations were detected at very low levels from July to February. During this time period population levels were below the low incidence threshold used by the Mexican Fruit Fly Campaign (CNCMF) as an action threshold indicating that populations are low enough to start a sterile fly release program for eradication purposes (CNCMF, 1993). Populations peaked during the months of March and April when temperatures in the region started to increase (Figures 9-3 and 9-4). Despite the population peak, levels are still low enough and do not exercise enough pressure to infest avocado fruits which are not the natural hosts of this or any other Anastrepha species (Hernandez-Ortiz, 1992). Furthermore, as Figure 9-3 shows Hass avocados are harvested throughout the year. However, the main harvest season is from October to May when around 60 percent of the total production is harvested (Paz Vega, 1989). During most of this time (October to February), A. ludens population levels are below 0.01 FTD, day which is the low-incidence threshold (Enkerlin et al., 1994). Throughout the experiment, avocado fruits were sampled from the orchards where MacPhail traps had been placed. Fruits were systematically gathered from the ground and from the tree. A total of 2,311 kg (12,638 fruits) were gathered and dissected. No eggs or larvae were ever found in the fruits. Moreover, during the harvest season Plant Protection Official Inspectors assigned to agricultural districts 087 and 088 in Michoacan (which cover practically all the avocado growing regions sampled) sampled, in packing facilities, around 101 tons (405,534 fruits) with negative results in detection of immature stages of the pest (Santiago et al., 1994). As the results clearly show, science provided basic information to assess, through a pest risk analysis, the feasibility of exporting Hass avocado fruits to the United States without jeopardizing the fruit industry in that country. Furthermore, it also provided the information required to mitigate risk, allowing for a systems approach implementation. Figure 9-5 schematically illustrates the role of science in solving a quarantine problem. It also shows how the information produced by the experiment, referred to here as a biological event,

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference Table 9-2. Susceptibility of Hass Avocados to A. ludens, A. serpentina , and A. striata—Forced Infestation in Fruits Attached to the Tree and in Fruits at Different Time Intervals after Harvest (Uruapan, Michoacan, 1993–1994)   A. ludens A. serpentina A. striata Fruit Infestation after Harvest (h) No. Fruits No. Pupae Pupae/ Fruit No. Fruits No. Pupae Pupae/ Fruit No. Fruits No. Pupae Pupae/ Fruit 0a 320 0 0 320 0 0 320 0 0 3 220 73 0.3 220 12 0.05 220 0 0 24 220 383 1.7 220 6 0.06 220 0 0 48 220 1,094 4.9 220 13 0.06 220 6 0.3 72 220 907 4.1 220 66 0.3 220 6 0.3 96 220 2,190 9.9 220 155 0.7 220 4 0.01 120 220 1,732 7.9 220 154 0.7 220 5 0.02 a Fruits subjected to infestation on the tree.

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference FIGURE 9-3. Seasonal Fluctuation of Anastrepha ludens Populations, and Minimum and Maximum Temperatures in the Hass Avocado Production Region of Michoacan, 1993–1994 FIGURE 9-4. Seasonal Fluctuation of Anastrepha ludens Populations and Hass Avocado Harvest Period in Michoacan, 1993–1994

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference FIGURE 9-5. Role of Science in Solving Quarantine Pest Problems

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference was used in a systems approach program to mitigate the risk of pest establishment associated with moving Hass avocados to the United States. CONCLUSIONS Under laboratory and field forced infestations, Hass avocado fruits are a good host of A. ludens, an average host of A. serpentina, and a poor host of A. striata. Hass avocado fruits attached to the tree are resistant to forced infestations of the three Anastrepha spp. evaluated. Hass avocado fruits are also resistant to infestations under natural field conditions The resistance observed is biochemical and ecological, not physical or morphological. GENERAL CONSIDERATIONS Biological sciences should always play a key role in solving pest quarantine problems. Science provides information to assess feasibility based on levels of risk, and it also provides information to mitigate risk. The scientific approach should include a multidisciplinary group of scientists in order to have a comprehensive understanding of pest-host relations. Evaluations of natural field infestations should be mandatory over laboratory and field forced infestations for pest risk assessment. Putting together a binational research team and a follow-up through site visits were key components on reaching the experimental goals. The overall scheme used in solving the Hass avocado quarantine dispute can be considered an effective model in solving quarantine problems. REFERENCES Armstrong, J.W., W.C. Mitchell and G.J. Farias. 1983. Resistance of ''Sharwil" avocados at harvest maturity to infestations by three fruit fly species (Diptera:Tephritidae) in Hawaii. Journal of Economic Entomology 76:119–121. CNCMF (Campaña Nacional Contra Moscas de la Fruta). 1993. Manual de opraciones de campo. Documento oficial no publicado. Dirección General de Sanidad Vegetal SAGAR. Coyoacán, México. Enkerlin H.W., J. Reyes F., A. Bernabe A., J.L. Sanchez P., J. Toledo A, and M. Aluja S. 1994. Estatus del aguacate Hass como hospedero de tres especies de moscas de la fruta del género Anastrepha, (Diptera:Tephritidae), bajo condiciones forzadas en laboratorio y campo, y bajo condiciones naturales en campo. Campaña Nacional Contra Moscas de la Fruta. Dirección General de Sanidad Vegetal, SARH. Agrociencia serie Protección Vegetal 4(3):230–348. Hernández-Ortiz, V. 1992. El género Anastrepha Schiner en México (Diptera:Tephritidae)., Veracruz, México: Instituto de Ecología, A.C., Xalapa. Oi, D.H., and R.F. Mau. 1989. Relationship of fruit ripeness to infestation in "Sharwil" avocados by Mediterranean fruit fly and Oriental fruit fly (Diptera:Tephritidae). Journal of Economic Entomology 82:556–560.

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference Paz Vega, R. 1989. Mexican avocados: threat or opportunity for California? California Avocado Society, pp. 87–106. Santiago M., G., W. Enkerlin H., J. Reyes F., and V. Ortiz G. 1993. Ausencia de infestación natural de moscas de la fruta (Diptera:Tephritidae) en aguacate Hass en Michoacán, México. Campaña Nacional Contra Moscas de la Fruta. Dirección General de Sanidad Vegetal, SARH. Agrociencia serie Protección Vegetal 4(3):349–357. Sarooshi, R.A., D.R. Blundell, and D.L. Peasly. 1979. Blemish and abnormalities of avocado fruit. Agricultural Gazette of New South Wales 90:18–20. SAS Institute. 1988. SAS User's Guide, release 6.03 ed. Cary, North Carolina: SAS Institute. Smith, D. 1973. Insect pests of avocados. Queensland Agricultural Journal 99:645–653. THE HASS AVOCADO CASE: A POLITICAL SCIENCE PERSPECTIVE DAVID VOGEL Haas School of Business, University of California, Berkeley Since 1914, the import of the Hass avocado from Mexico into the United States had been forbidden on the grounds that the fruit was a host of various fruit flies and seed pests whose introduction into the United States would threaten the American avocado crop. Recently, this ban has been lifted. Although still subject to various restrictions, Mexican avocados can now be exported. At one level, this significant policy shift reflects the development and implementation of a set of scientific protocols and procedures that have provided assurance that the fruit sold in the United States does not contain these harmful pests. But although scientific arguments and evidence may have been a necessary condition for trade liberalization, they were certainly not a sufficient condition. It was politics, in the form of the North American Free Trade Agreement (NAFTA) that provided the necessary impetus for the ending of an embargo after more than 80 years (Vogel, 1995). For at least two decades Mexico had been pressuring the United States to come up with a protocol that would allow the importation of Mexican avocados. A number of specific proposals were explored during the 1970s, and considerable progress appeared to have been made in developing procedures that would provide adequate protection to American growers. At one point, the U.S. Department of Agriculture (USDA) was considering proposing a rule in the Federal Register that would have made it possible to begin exploring the implementation of these procedures. However, the California Avocado

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference Commission, with the assistance of California Senator Cranston, persuaded the USDA not to issue such a rule. Negotiations between the United States and Mexico continued and there was a good deal of additional scientific research, but the considerable political influence of the California avocado industry effectively prevented the adoption of any protocols or procedures that would have relaxed the embargo and thus exposed California growers to international competition. This represented a major setback for Mexican growers who had made substantial progress in devising various means of preventing exports of their crop from endangering American agriculture. During the intense domestic debate over the adoption of a free trade agreement with Mexico, major segments of American agriculture opposed congressional approval of NAFTA for straightforward protectionist reasons: They did not want to have to compete with less expensive Mexican agricultural exports. Among the agricultural producers opposed to NAFTA was the California avocado industry who clearly understood that the approval of this trade agreement would reduce their ability to keep out lower-priced Mexican produce and thus reduce their profits or market share. NAFTA was, of course, approved. Not surprisingly, among the first requests from Mexico following its approval was for an ending of the American restriction on exports of avocados. After some delays, the USDA issued new regulations that ended the embargo, and Mexican avocados are now available for sale in the United States under various conditions. In effect, what NAFTA did was to end the monopoly of California avocado growers over policy making at the USDA. Prior to NAFTA, there was no domestic constituency that favored the relaxation of import controls. To be sure, such a relaxation was clearly in the economic interests of American avocado consumers, but they were not politically organized. No American consumer group chose to focus on this issue and it received little or no press coverage. The typical American consumer neither knew nor cared that they were paying above world market prices for avocados, and as a result their interests were not represented in the policy process. What NAFTA did was to give political voice to a constituency that favored the relaxation of import controls, namely Mexican avocado growers. Trade agreements, by definition, globalize domestic politics: They explicitly give foreign producers a claim on domestic policy making. At the same time, trade liberalization also serves to give foreign producers domestic allies. With the approval of NAFTA, American producers now have the opportunity to gain access to the Mexican market. These producers now have the ability to demand that Mexico eliminate or reduce its use of sanitary and phytosanitary (SPS) standards to keep out their products. Thus the avocado agreement can be seen as part of a broader, reciprocal agreement to reduce the use of SPS standards as trade barriers on both sides of the border—a dynamic that NAFTA made possible. The approval of NAFTA served to politically isolate California avocado producers. While NAFTA was being negotiated, their interests coincided with

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Incorporating Science, Economics, and Sociology in Developing Sanitary and Phytosanitary Standards in International Trade: Proceedings of a Conference those of other American growers who opposed trade liberalization with Mexico. But once NAFTA was approved, each crop was on its own. Significantly, in their last-ditch effort to prevent the opening of the American markets, the California avocado growers received only token backing from other growers, each of whom was now focused on protecting their own markets. The liberalization of the American avocado market represents an almost textbook case of the benefits of trade liberalization. For what NAFTA did was to subject American "scientific" restrictions on avocado imports to international scrutiny. And it turns out that they were unable to survive such scrutiny. In effect, NAFTA made possible the triumph of science over economics. Without NAFTA, or more specifically, the access that NAFTA accorded the scientific claims of those who favored trade liberalization, the various scientific protocols and procedures that had been devised to permit the importation of Mexican avocados in ways that did not endanger American growers would have remained stillborn. From this perspective, this case illustrates trade liberalization at its best: It changed a regulation whose only purpose was to protect the economic interests of American producers, and, as a result of this change, American consumers are better off. At the same time, it is important to keep the significance of this case study in perspective. This dispute over SPS standards was primarily an economic one: It pitted the interests of American avocado growers against Mexican growers. There was no question of consumer safety; what was in dispute was the "safety" of domestic growers. American producers and consumers had opposite interests. Because the former could not claim that the latter's health and safety would be endangered if the importation of Mexican avocados was permitted, American consumer groups could not be mobilized to back the avocado ban. This stands in sharp contrast to, for example, the beef hormone dispute between the United States and the European Union, which does raise politically salient consumer health issues. Accordingly, European consumers and consumer groups have become important allies of protectionist producers. This makes the resolution of this dispute through appeals to "science" much more difficult. REFERENCE Vogel, D. 1995. Trading Up: Consumer and Environmental Regulations in a Global Economy. Cambridge, Mass.: Harvard University Press.