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.
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