Introduction. Apples are potentially subject to blue mold decay caused by Penicillium expansum if
stored at 1 °C for three or more months or if wounded during handling. Results from trials with apples
contaminated with conidia of P. expansum and fumigated in small chambers with acetic acid (AA) vapor indicated
that fruit could be sterilized to reduce decay without effect on fruit quality. The objective of this study was to
determine if larger quantities of apples treated with AA vapor would have less decay after storage and/or wounding. It
was also important to determine if fumigation would affect apple quality and aroma. Materials and methods. Apple
cultivars were harvested at commercial maturity for use in AA fumigation trials. Apples artificially or naturally
contaminated with conidia of P. expansum were fumigated with AA vapor in a 1 m3 gas tight chamber at
10 °C for 1 h to 24 h or dipped in 450 μg thiabendazole × L-1 solution. Fruit fumigated
in standard wooden or plastic apple boxes, or small wooden bins were either wounded and evaluated for decay after a week
at 20 °C or stored at 1 °C for three or more months and evaluated for decay. Then apple quality was
assessed. Results. Apples naturally contaminated with Penicillium spp. that had been stored at
1 °C in air storage and treated with AA vapour had 50% less decay than the control fruit. In another
experiment, AA fumigation was as effective as thiabendazole in reducing decay. AA fumigation reduced decay of fruit
coming out of storage for apples stored for 3 months, and a second AA fumigation reduced infection of wounds on these
same apples. AA fumigation before storage did not affect apple quality or vinegar aroma. Discussion. AA fumigation
showed great potential for reducing decay in stored apples. It could be used as an organic alternative to synthetic
fungicides for control of blue mold decay.