Vineyard surveys of Corinth raisin cultivar carried out in the Peloponnese region of Greece during 2002 and of wine-producing grape cultivars (Cabernet Sauvignon and Grenache Rouge) on the island of Rhodes, Greece, during 2003, demonstrated the occurrence of various Aspergillus spp. in berries of bunches at harvest. Aspergillus niger and A. carbonarius were predominantly isolated from sampled berries. Although the prevailing Aspergillus spp. isolates belonged mainly to A. niger aggregate, isolates of A. carbonarius were by far the most efficient Ochratoxin A (OTA) producers as revealed by the enzyme-linked immunosorbent assay test. This study provides the first evidence concerning the composition of Aspergillus populations in raisin and wine-producing vineyards and offers convincing data for their ability to produce various levels of OTA in Corinth raisins and wine-producing grapes in Greece. Furthermore, it demonstrates that chemical applications with the fungicide Switch, especially under low to intermediate Aspergillus infection of vineyards, could both significantly reduce the occurrence of OTA-producing Aspergillus spp. and restrict sour rot severity. In contrast, vineyard applications with the fungicides Carbendazim or Chorus were ineffective in controlling the fungus in Corinth raisin cultivar.