Evaluation of Ethyl Formate, Phosphine, and Their Combination to Disinfest Harvested Celery against Purple Scum Springtails

Export celery (Apium graveolens var. dulce) from Australia has been affected by a natural infestation of purple scum springtails (Hypogastrura vernalis). These insects live inside the celery head, contaminating fresh celery, but do not cause any visible damage. As a result, purple scum springtail-infested celery has led to rejection for export with an impact on market value for fresh produce. In this study, fumigation with ethyl formate (EF), phosphine (PH3), and their combination on mortality of purple scum springtails in naturally infested celery was evaluated. Laboratory experiments were conducted using concentrations of 50, 60, and 90 mg.L-1 of EF for 1, 2, and 4 hours; 1, 1.5, 2, and 2.5 mg.L-1 of PH3 for 2, 4, and 6 hours; and 20, 30, and 40 mg.L-1 of EF combined with 1 mg.L-1 of PH3, for 2 and 4 hours at the laboratory temperature 25 degrees C. Complete control was achieved at 90 mg.L-1 of EF for 2 hours; however, phytotoxicity was observed in celery treated by EF at all concentrations. PH3 at 2.5 mg.L-1 achieved 100% mortality within 6 hours, and no phytotoxicity was evident. Mortality of 100% was achieved also at 30 and 40 mg.L-1 EF combined with 1 mg.L-1 of PH3 for 2 and 4 hours exposure time; however, phytotoxicity occurred with EF alone treatments and with the combination. From these data, we conclude that PH3 alone has potential as a fumigant for the preshipment treatment of celery infested with purple scum springtails.