Use the diluted bleach spray. It will help with any that are not already deeply infected. I lost most of my onions and garlic one year to this stuff and after that if I ever saw any indication of it I used the bleach spray and have had no problems since. I also went to heavily mulching my onions and garlic with cypress mulch. The disease is caused by splash back from heavy rains and if it is in the soil it can get into the drenched plants. If it is caught early enough and you get a break from the rain the bleach spray will really help and also reduce the incidence of the problem in the future. I wouldn't worry about the wind because drift won't affect any nearby plants negatively but you could get some bleaching of your britches legs so wear some old pants. Make sure to add a bit of dish washing liquid to the spray so it will wet the waxy onion stems. It takes more soap than when spraying tomatoes and it doesn't hurt to go with a slightly stronger mix. You might want to read this thread.
http://tomatoville.com/showthread.ph...t=bleach+spray
You need to get a garbage bag and go out and pull any onions and garlic where the problem has caused softening or rotting in the stalk just below the new growth. The smell will be really bad from my past experiences with it but removing the worst plants will help some. I still remember the stench and flies from the last time it hit my garlic and onions.
Bill