Is phosphine an ideal candidate for fruit fly disinfestation in Java apple, Syzygium samarangense?

Abstract

Java apple, Syzygium samarangense, a nutritionally rich fruit species cultivated in Southeast Asia is prone to fruit fly infestation. Since no commercial management protocols currently exist for disinfesting java apple against fruit flies, the present study investigated the suitability of phosphine fumigation for post-harvest disinfestation of java apple fruit. Fruit exposed to gravid female Bactrocera dorsalis overnight were subjected to phosphine fumigation at concentrations ranging from 0.14 to 2.78 mg/L for 24, 48 and 72 h at ambient conditions. Gas chromatographic analysis of the PH3 concentration revealed that approximately 65% of phosphine gas was lost in treatment chambers fumigated with highest concentration of 2.78 mg/L for 72 h. B. dorsalis eggs could be mitigated by exposing java apple fruit to a concentration × time product of 16.67 mg/L-h of PH3 or more. Fumigating fruit at PH3 concentrations below 0.69 mg/L for 24 h and 48 h did not significantly change the color of treated fruit. Furthermore, the texture of the fruit post PH3 fumigation remained unaffected. Phosphine treated java apple fruit showed no trace of phosphine residues at exposures shorter than 72 h. In conclusion, phosphine can be a viable treatment for the management of B. dorsalis eggs in S. samarangense fruit at lower concentrations and shorter durations without affecting the fruit quality.