Replanting and fireblight

I've been dealing with some fireblight the last couple years, trying to stay ahead of it with pruning. I lost two Prairie Spy trees to the nasty bacteria. I know the bacteria is everywhere, but does it particularly stay in the soil? Is it a mistake to plant new trees in the same spot? Thanks!

Pat McBride
Twin Oaks Orchard
Zone 4b in Minnesota

Fireblight infection is only likely if live tissue in the orchard is already infected. So, provided you have removed all infected trees or wood, you are safe. This does mean, however, that root sections that may harbor the bacterium throwing up infected shoots. So be thorough. Fireblight dies out when not on a suitable host, which includes aged prunings. Once live tissue dries out, conceivably even a full tree, it is unlikely to be a vector.

A point worthy of bringing up with any disease is overall management. It is obvious that trying to remove any trace in the orchard is good form, but what is often overlooked is how it got there in the first place. Unless a pathogen hitched a ride in on stock, it is more than likely that a problem disease is giving us trouble because it is indigenous. Fireblight has a lot of hosts besides the pome fruits, and many fungal diseases have an ungodly amount of places to hide. This means that plant and soil management and cultivar choice are often more important than an attempt at clean slate agriculture.