[Oliveview]

We have our onions (or did have) hanging from the patio roof (tin roof) and some of them have developed a kind of black powdery mildew, any ideas?  I´ve taken them down this morning and put them in a plastic box (with holes) and put them in the hall- the coolest place hopefully.  Will they survive the winter??
Pamela

[8doubles]

I think onions need more ventilation than they will get in a plastic box and they would store better hung up in the sunlight as long as they do not get too warm.
Tin rooves can be very prone to condensation which will encourage various mildews and moulds which the UV rays in sunlight inhibit.

With luck it is just on the outer layer of skin which you may be able to remove.