BACKGROUND: Aculus olearius Castagnoli is a recently recorded species that damages olive fruits in the Mediterranean basin of Turkey. Thus, the effects of Eriophyid mites (Aculus olearius Castagnoli and Aceria oleae (Nalepa) (Acarina: Eriophyidae) on the olive fruits from Ayvali{dotless}k variety in southern Turkey were studied for the first time in terms of some physical parameters and chemical constituents including some individual phenolics. RESULTS: The Eriophyid damaged fruits had higher L* values (lighter colour) and tyrosol level (37.53 mg kg-1) than the undamaged fruits (28.51 mg kg-1) in August. In contrast, Eriophyid damaged fruits were darker in colour and had lower levels (25.77 mg kg-1) of tyrosol than those of undamaged fruits (79.14 mg kg-1) in October. Eriophyid damaged samples had higher values of vanillic acid than the undamaged samples. An increase in the average concentrations of hydroxytyrosol and p-coumaric acid was observed in the fruits harvested in August, whilst the oleuropein content decreased. CONCLUSION: The harvest in October can be recommended regarding the higher dimensional values, total oil, dry matter and oleuropein contents. But the interaction between harvest time and Eriophyid damage was found effective in terms of tyrosol content and skin colour; as tyrosol values were lower in the fruits harvested in October and the fruits were darker. The resistance of undamaged fruits against Eriophyid damage can be linked to high tyrosol content of these fruits. © 2010 Society of Chemical Industry.