[hubballi]

This has happened consistently for the last 5 years. You would be forgiven for thinking at a quick glance that they are black fly but closer they are actually small round, oval shaped holes.

Does anyone know what it can be  ? I have never found anything living on them, just the increasing evidence.

[Aunt Sally]

I think they may have been knibbled by something.  Very odd.

[Salmo]

Something is biting the leaves when they are tiny. As the leaves expand the holes grow bigger and ragged. Could be thrips. There are lots of species of thrips. One sort we see are thunderflies which live on wheat. As the wheat ripens the thunderflies leave and are very annoying on hot sultry days..

[hubballi]

Do you mean black corn flies ?