Here's another reason to hate squirrels.
When getting my trees ready for winter, I pull the tree out of the pot by the trunk to check the roots. I found that two trees I purchased at the end of 2010 were RKN infected, it had progressed pretty badly, too.
I had a lot of problems with squirrels digging in my pots this year until I built a shelter for the pots to stay in. I'm sure you know where this is headed....
In checking my trees prior to winter, I found a couple of them that showed initial signs of RKN, but only near the TOP roots, which is strange, most seem to start from the bottom (ground side) up. I started flipping through pictures I've taken and noticed that the trees which had problems were placed around the purchased trees that came with RKN infected soil.
So, basically, it seems that squirrels were digging in the infected pot, then digging in my clean pots and transferring RKN over ... OR they were digging and kicking infected soil over into the clean pots.
Either way, it sucks, it's BS, now I get to airlayer trees, and I have all the more desire to kill every damn squirrel that comes on my property.