I don't know if it matters what you use as long as it blocks the developing tubers from the sun in order to prevent solanine from developing wherever the sun hits the tubers. As you said, fungal spores are everywhere anyway....in the soil, in the mulch...spreading on the air. If you want to spray with fungicide and then mulch, it might help and likely won't hurt. If rain falls soon after you spray, it may wash off the fungicide so keep that in mind. I planted my potatoes 9" deep and then have 4-6" of mulch atop the soil, and that has to be good enough. The nice thing about densely planted potato beds is that the foliage shades the ground pretty well too, so the plants most vulnerable to sunlight striking the tubers would be only the southernmost row along the edge of the bed, and it is well-mulched. My potato plants are about 2-3' tall and in bloom, so are right on schedule for as early as I planted them, which I think was mid-February. I could rob some new potatoes now, but probably won't. I don't like disturbing the tubers that are developing. I also don't like handling their foliage while they're wet as that can spread disease. It seems like mine are wet every morning from dew. The earliest variety should be ready for harvest in about a month, and the later varieties about a month after that. This spring's weather has been kind to the potatoes as they really haven't had to deal with any cold weather to speak of.

Thanks, Dawn.

So, you won't add anything else to your potatoes even though they are 2-3' tall? Mine were planted about 6 inches deep and I added soil last week. I think I will spray them tomorrow, dump a bag of leaves on them and hope for the best. Mine were planted a month later than yours--on St. Patrick's Day...and are also densely planted. They are in an odd, really tall bed--it's close to 3 ft. tall.

Any tricks to digging potatoes without cutting the potato? I always damage mine...or at least a few.