I’m not sure. We had no problems for a good while then just a few infected plants, We used to remove the infected plants quickly but the OR spread through the rows over about 10 years on Navaho but never infected the adjacent rows of another variety
We also changed from removing the old prunings and burning them to flailing the old prunings in place.
One easy way to spread the disease is by mowing over an infected and spreading the spores up and down the row.