If you had problems with fire blight last year, this is for you: The best preventative measures for fire blight are the application of streptomycin at bloom to prevent blossom blight and the application Apogee at petal fall to reduce shoot blight. Yes, Apogee is expensive. It is worth every single penny.
Apply streptomycin just as blossoms begin opening and repeat every 3-4 days if weather is favorable or blossom blight infection persists. Streptomycin is most effective when applied the day before or the day of an infection event. Be especially diligent in your fire blight program if you have blight susceptible varieties (Jonathan, Gala, Ginger Gold, Ida Red, Jonagold, Fuji, Lodi, etc.) in combination with M-26, M-9 and/or Mark rootstocks and/or interstems. For young trees, excess nitrogen to drive growth makes trees more susceptible to fire blight, especially Evercrisp and other Fuji hybrid cultivars.