The best method to prevent the fire blight bacterium from overwintering is to:

Preventing the fire blight bacterium from overwintering is best accomplished by pruning out diseased branches. This method effectively removes the source of the pathogen and minimizes the chances of it spreading. Fire blight often manifests through the infected wood and can survive in these areas, allowing it to potentially reinfect plants in the subsequent growing season.

By removing the affected branches, you not only eliminate the bacteria but also promote healthier growth in the remaining plant tissue. This practice is crucial in managing fire blight, as it directly disrupts the lifecycle of the bacteria and reduces the inoculum available for future infections.

Other methods, while potentially beneficial for plant health, do not specifically target the overwintering aspect of the bacteria. Using fungicides, for instance, is generally more effective on fungal pathogens rather than bacterial ones. Increasing irrigation can create conditions conducive to bacterial proliferation rather than control. Utilizing resistant crop varieties is a good long-term management strategy but does not directly prevent the bacteria from overwintering in infected materials already present in the environment.