Comparative studies on the efficacy of gamma irradiation, heat, refrigeration and combined treatments as a quarantine treatment for mango fruit

The development of the mango seed weevil was found to parallel the growth and maturation of mango fruit. In the cv Totapuri, fruit harvested at the full matured stage showed mostly adult insects while fruit harvested at 85% maturity had larger proportions of grub and pupae. Gamma irradiation at 0.30 kGy and above interfered with the development of grub and pupae into adults. Those adults present at the time of irradiation and surviving the treatment were docile and inactive, particularly after exposure to 0.5 kGy or more. Results indicate the need for irradiating fruit at the hard green unripe stage, soon after harvest, when the population of adults is comparatively low and any adults present are not physiologically mature to emerge from the seed by burrowing through the endocarp. Irradiating weevil infested mangoes to doses of 0.30 to 0.75 kGy did not result in complete mortality of the adults, even after 3 weeks at ambient conditions or when held for a similar duration at 11 ± 1 deg. C followed by 8 days at ambient temperature (a storage period adequate for overseas transport and ripening of fruit). A hot water dip at 49 deg. to 50 deg. C for 120 min appears to be lethal to the various developmental stages of the insect but may cause skin damage to the fruit. Irradiation at doses up to 0.75 kGy or a hot water dip at 47 deg. to 48 deg. C for 120 min did not adversely affect the quality of fruit on ripening. (author). 4 figs, 11 tabs