[Goosegirl]

My greenhouse ones are fine but the outdoor ones have some light brown streaks on their leaves. Anyone know what it is due to?

[Baldy]

Rust maybe?

There are a few different possibilities though:
https://www.google.co.uk/search?q=sweetcorn+leaf+rust&tbm=isch&tbo=u&source=univ&sa=X&ved=0CC4QsARqFQoTCMOTwvje2scCFQnWGgodQHQJXg&biw=1221&bih=787

Pip pip,
Balders

[Kleftiwallah]

I've just cleared out our sweetcorn block and I think it is normal.

Cheers,  Tony.

[Snoop]

When mine get a bit thrashed around in the wind, the leaves sometimes get brown streaks and then fray.

[Goosegirl]

Mmmm - had a look on top and under the leaves but can't see any rust spores and not had much wind lately, so the jury's out. Their cobs are nearly ready so hopefully they will be ok - thanks.