Eupoecilia ambiguella primarily attacks fruiting organs. The depredation in the first generation can be spectacular but has little effect on the harvest. On the other hand, damage from the late summer generation can promote gray rot and affect the quality of the wine. This indirect harmfulness is observed before the harvest. It is due to bites and punctures present on the berry which facilitate the development of microorganisms on the bunch.

 

In addition to the risk of gray rot ( Botrytis cinerea ), other rots can develop, for example black rot caused by Aspergillus spp. in Mediterranean vineyards which is sometimes ochratoxinogenic and poses significant health problems.

The damage caused by Cochylis, like that of Lobesia botrana , can be very severe. They often vary from one year to another, with sometimes more than 60% of the bunches affected and causing losses of the order of 1 hectolitre of wine per hectare.