Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 19, 2008
Publication Date: April 18, 2008
Citation: Leesch, J.G., Smilanick, J.L., Tebbets, J.S. 2008. Methyl bromide fumigation of packed table grapes: Effect of shipping box on gas concentrations and phytotoxicity. Postharvest Biology and Technology. 49:283-286. Interpretive Summary: Currently, table grapes being shipped to Australia require fumigation to prevent the entry of mealybugs on the grapes. A schedule for grapes shipped in wood veneer boxes and cardboard boxes exists for this purpose, but does not allow the grapes to be fumigated in polystyrene boxes because there have been reports that the polystyrene adsorbs more of the methyl bromide fumigant.These tests were designed to answer the question of whether or not the current fumigation schedule for veneer boxes would be applicable to the polystyrene boxes. Tests showed that although the final concentrations of methyl bromide at the end of fumigation was different in the polystyrene boxes as compared to the veneer boxes, the total exposure to the fumigant was the same as expressed by the concentration times time product. Thus the conclusions were drawn that no adjustment in the current schedule was necessary to effectively fumigate the grapes in polystyrene boxes.
Technical Abstract: Current methyl bromide schedules for table grapes to control mealybugs are approved for fruit packed in Toyon Kraft Veneer (TKV) boxes. The question arose concerning equivalence of exposure to methyl bromide if an Extruded Polystyrene (EPS) box was used in lieu of the TKV box for table grapes being shipped to foreign countries. Fumigations of ‘Crimson Seedless’ table grapes packed in either EPS or TKV boxes were conducted for comparison of methyl bromide gas concentrations and fruit quality using Australian methyl bromide treatment schedules. Methyl bromide gas concentration expressed as the concentration x time product (g'h/m3) (CxT) was the same or higher for the EPS box compared to the TKV box. Methyl bromide gas concentrations were higher for EPS boxes at the start of the fumigation, but lower than TKV boxes at the end of the exposure period (2 h) due to a higher sorption rate. Internal browning, characteristic of methyl bromide phytotoxicity, was absent or very low (< 1.7% of the berries) for both box types, and no other injury attributable to exposure to methyl bromide was evident. EPS boxes should be suitable for shipping table grapes to export markets based on equivalency of concentration x time products. If methyl bromide readings at the end of the 2 hr exposure period are used for equivalency, data show an increase in methyl bromide dose of 4 g/m3 when EPS boxes are used to replace TKV boxes for shipping table grapes.