What do you mean by "top rot"? Do you mean the leaves or the bulbs? If you can describe the problem a little more, we can try to help you figure out the best way to keep your onions.

Not meaning to hijack the thread, but only to piggyback on it...

I got good top growth this year, and good bulb size and harvested when the leaves fell over, as I have other years. I have some drying boxes that I made (ventilated wood sides with hardware cloth bottoms). All were put in there (single layer) two or three weeks ago. It appears that the bulbs never sealed at the top and are starting to rot from the point where the leaves were down to the center of the onion. The outer rings of the onion are solid and fine, but the very top (point on the bulb opposite the root) is spongy and moist.

Thoughts anyone?

Wolverine, I've had that problem before.
I found it under 2 circumstances.
One is when when the onions had bad downy mildew before falling.
The other is when the onions have bolted and I've broken off the flower top. Then the rain can get in the hollow stem and start to rot the bulb at the point you mention.

If neither of these options sound right to you, could it be that you had heavy rain while the bulbs were drying down?

It doesn't sound like you did anything wrong while curing the bulbs....

Either way, I'd think they won't keep well. Sorry to hear about it.

Madroneb,

Thanks for your prompt, though disheartening, reply. I was hoping for a miracle solution.

We did, indeed, get heavy rain right after I pulled my reds and had them drying in the field. The rain was unexpected, though overall welcomed, and some of the heaviest I have ever experienced. The next day I was out, removing my bulbs from the mud, and expecting the worst.

I had gotten my whites out earlier, and for the most part they are in much better shape.

Well, hopefully I'll have another chance next year...

@ original poster -

Well, you can just strip off the rotted layers. A root can look perfectly wretched and ready for the trash bin, yet if you will peel off the rotten bits, you'll find 3/4 of the onion is still good. That is the wonder of alliums.