There are a lot of Extension Bulletins on fireblight; this one from the Pennsylvania State Universuty looks very good to me: https://extension.psu.edu/apple-disease-fire-blight

You can find answer for your question in the article:

https://www.planetnatural.com/pest-problem-solver/plant-disease/fire-blight/

Dear Nina Shishkoff, Mohammad Abdulhai and Stefan Zimmermann

I appreciate you answer my question. It has really helped me.

Thanks,

Severely cut and incinerate the dried twigs and treat with defense stimulators such as Fosetyl aliminium or Acebenzolar-S-Methyl.

Hy sir

I can I know where r you had seen fire blight infection??