KK from NJ said:

I'm having trouble picturing this. I think you mean you built a box
to hold the straw, right?

Sorry I wasn't clear. The mold is in the straw. Its full of it

the cage
http://members.aol.com/kkfromnj/cage.jpg/

and if you can see it, the mold
http://members.aol.com/kkfromnj/mold.jpg/

I couldn't see the pictures (pages of weird characters in the browsers I use),
but taking Aaron's word for it that the plants are healthy, you may have nothing
to worry about.

I plant my seed potatoes in the soil and mulch with chopped straw as they grow.
(In fact, I think I ought to top off the mulch this weekend.) The mulch usually gets
a bit rotten at the bottom, sometimes with weird ear-shaped fungus thingees on
it. The potatoes underneath are fine though (unless they've been nibbled by
voles, which is a whole 'nother problem).
--
Pat in Plymouth MI

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)