Today at the allotment one of my fellow allotmenteers showed me some of his sweetcorn plants with some strange damage to the lower leaves. They looked liked they had thin strips scored along the length so much so you could see through them. I thought of slugs or snails but they would eat all the leaf and anyway he had put slug pellets down (I have also never had problems with slugs eating sweetcorn leaves)
Has anyone any ideas.
The same has happened to mine. I wondered if it was the pesky pigeons.
His plants were under netting so I don't think it can be our feathered friends.
I would say slugs. Go to your allotment about 6 am and you will see them still at it. The small slugs seem to like the sweetcorn. I leave mine covered in plastic bottles until they are big enough to cope.
Look up Thrip and / or Leaf Miner damage for comparison, difficult to tell from your description but these were the first things that came into my mind!