Effects of fungicide application and addition of a sticker adjuvant to the fungicide on the occurrence of fruit rot in Satsuma mandarin after refrigerated maritime transportation from Japan to Singapore

Several experiments were conducted to establish an efficient system for controlling fruit rot when exporting Satsuma mandarin to Singapore. A total of 110 isolates of Penicillium digitatum obtained from 44 orchards in Wakayama Prefecture were assayed for sensitivity to thiophanate-methyl, benomyl, and iminoctadine triacetate. Of these isolates, 8.2 percent showed resistance to thiophanate-methyl and benomyl, and all isolates showed sensitivity toward iminoctadine triacetate. These three fungicides seemed to be effective. In a refrigerated maritime transport experiment in which Satsuma mandarin was taken from Japan to Singapore, spraying thiophanate-methyl wettable powder before harvesting suppressed the occurrence of fruit rot 19 days after devanning to about 41% of that of an untreated load. Addition of a paraffinic sticker adjuvant to thiophanate-methyl wettable powder or iminoctadine triacetate liquid decreased the rate of occurrence of fruit rot in an inoculation test of P. digitatum following artificial precipitation and reduced the occurrence of fruit rot 14 days after devanning in a refrigerated maritime transport experiment in which Satsuma mandarin was taken to Singapore. Adding a paraffinic sticker adjuvant to fungicides sprayed before harvesting was considered to improve the efficacy of fruit rot control after refrigerated maritime transportation of Satsuma mandarin from Japan to Singapore.