Bologna, Italy

Anyone any idea what might be causing this problem? Little tiny pinholes in foliage and scorching round them - it's not just brussel sprout plants, but broccoli and rocket, too. Could it be caused by heat/drought? I haven't noticed any wildlife at all on the leaves, and new growth is unaffected to start with. It's just older leaves that seem to have the problem.

• 19 Sep, 2011