The Mediterranean Fruit Fly and the United States: Is the Probit 9 Level of Quarantine Security Efficient?

Cold treatment periods, and associated levels of quarantine security, that maximize net US welfare under USDA’s current medfly detection and control program are examined using a deterministic bioeconomic optimization model. As anticipated, the efficient level of quarantine security is shown to increase with indices of medfly pressure (initial infestation rates) in areas in which the medfly is known to exist (the QCs). Efficient cold treatment periods and weighted mean medfly survival rates are 8, 11, and 12 days and 5.0 × 10–2, 1.7 × 10–3, and 5.2 × 10–4 under low, moderate, and high initial infestation rates, respectively. When model output is averaged across initial infestation rates, an 11-day cold treatment period, resulting in a weighted mean medfly survival rate of 1.6 × 10–3, maximizes US welfare. These findings suggest that the current minimum cold treatment period of 14 days and the current objective of US cold treatment policy—the probit 9 level of quarantine security— are economically inefficient. Adopting the 11-day cold treatment period is shown to increase US social surplus by an annual $24.9 million, of which $21.5 and $3.4 million would accrue to US consumers and producers, respectively, and QC producer surplus by an annual $24.8 million.