hazelnut worm

I think holes in hazelnuts are usually caused by weevils, and the way to stop these is generally by applying greasebands to the trunk of the tree. Where you have bushes, you may have to think of an alternative treatment.

Quote "Filbertworm is perennial problem and
occurs in virtually all hazelnut orchards" . Have seen this before so checked it out ... read http://www.croplifefoundation.org/Insecticide_Benefits/Crop_Studies/Combined_Document_Hazelnuts.pdf for more information on this.