The reddish spots are probably symptoms of the fungus Puccinia porri, commonly known as onion rust. Rust and purple blotch are common diseases attacking the foliage of onions. Fungicides can provide adequate control of these diseases. Bordeaux mixture (see copper fungicides) or sulphur can be used to control the disease. You also need to control weeds in the general area of your garden to eliminate alternative hosts for the disease.
Always read the pesticide label before applying crop protection chemicals and follow the label instructions exactly.
For more information on green onions, refer to: Onions—Bulb and Green Bunching.
