Forced Hot-Air Quarantine Treatment for Mangoes Infested with West Indian Fruit Fly (Diptera: Tephritidae)

Abstract

Quarantine efficacy for mangoes against the West Indian fruit fly, Anastrepha obliqua (Macquart), was demonstrated using a forced hot-air system. Extrapolation from the probit model fitted to preliminary experimental data indicated a 99.9968% mortality at pulp temperature of 48.1°C. The probit analysis showed that goodness-of-fit was poor, but that this was caused by large errors at the lower temperatures rather than systematic departure from the model. We killed an estimated 109,839 larvae with no survivors in 2,221 mangoes giving >97% confidence that the mortality was greater than the probit 9 level. By running air temperature at 50°C, air speed at about 0.4 m3/s, and increasing humidity at a rate such that the dew point was always at least 2°C lower than the mango surface temperature, we were able to heat :the mangoes at a rapid rate without surface scald or other phytotoxic effects. We recommend that mangoes be heated until seed-surface temperatures reach 48°C and that air temperatures, air speeds, load sizes, and other factors determining rate of heating be determined for individual commercial systems. In our confirmatory tests, treatment time ranged from 101 to 213 min depending on mango sizes and numbers of boxes treated. Consumer panels, in the laboratory and made up of the public, found no difference in taste, odor, or overall acceptability but frequently judged treated mangoes superior to controls for appearance factors. Position of mangoes in the chamber was frequently a significant factor in panel ratings. More even heat distribution by such means as a reversible fan system may decrease this variation.