Pg. 4-9 Refinement of SO2 sheet application in combination with fumigation

During the 2002/03 season, a preliminary study was conducted, aimed at evaluating the efficacy of sulphur fumigation sheets. The results indicated that the sheets have a beneficial effect when placed in the bottom of litchi cartons containing sulphur fumigated fruit. During the 2003/04 season, a comprehensive set of trials was conducted. Refinements included the lowering of the original SO2 fumigation dosage, establishing the optimal placement of the sheets within the box and the assessing of paper liners for possible use in combination with the sheets.

From the results it is recommended that HLH Mauritius fruit be fumigated at full strength and that two sheets ( one on top and one at the bottom) be used, without a liner. This combination was found to be especially effective when shipping delays may require slightly longer storage periods, and did not increase the SO2 residues in the aril either.

With McLean’s Red, fumigation at half strength in combination with one sheet was the only treatment to result in acceptable aril SO2 residue levels. All other treatments (including full strength fumigation without any sheet) resulted in unacceptably high residue levels. Future research should focus on the relationship between maturity and the dosage rate at which the fruit are to be fumigated.

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