Forced hot-air quarantine treatment for mangoes infested with West Indian fruit fly (Diptera: Tephritidae).
Mangan R. L., Ingle S. J.
Author Affiliation: Crop Quality and Fruit Insect Research Unit, Subtropical Agricultural Research Laboratory, USDA, ARS, Weslaco, TX, USA.
Journal of Economic Entomology 85 : 1859-1864
Abstract : Quarantine efficacy for mangoes against Anastrepha obliqua 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. An estimated 109?839 larvae were killed, with no survivors, in 2221 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, the mangoes could be heated at a rapid rate without surface scald or other phytotoxic effects. It is recommended 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 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 differences in taste, odour or overall acceptability but frequently judged treated mangoes as 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.