- 1). Plant disease-resistant varieties of apple tree, such as Honeycrisp, Liberty and Red Delicious. Don't plant the least-resistant cultivars, including Fireside, Honey Gold and Wealthy. Although resistance does not equate to no disease risk, it does improve your chances of healthy apple tree growth, especially if you continue to have problems with fire blight annually.
- 2). Control cultural practices, including watering, pruning and fertilizing, to reduce the risk of fire blight. Plant trees only in locations with full sun and well-draining soil. Avoid watering during blooming. Apply nitrogen fertilizer only as required, according to soil test results. Too much fertilizer will encourage new growth, which is most susceptible to fire blight. Likewise, prune trees during the dormant season during dry weather to avoid stimulating excessive growth in the spring or creating wounds for bacterial entry.
- 3). Keep insect pest levels low to prevent possible disease spread. Some insects, such as leafhoppers, create wounds in trees that may act as an opening for the fire blight bacteria. Apply an insecticide according to label directions and use good cultural practices to minimize this potential.
- 4). Apply a copper-based fungicide or a streptomycin sulfate-containing spray on severe or annual infections. Apply fungicides multiple times as blossoms develop and open. Continue applying fungicide at five-day intervals on days when temperatures reach at least 60 degrees F, until blooming is over, advises the University of California Integrated Pest Management Program. Starting when blossoms fall, check trees on a weekly basis for signs of infection and prune out diseased limbs as soon as possible.
- 5). Prune diseased branches from dormant trees to prevent overwintering of fire blight. Make cuts at least 4 inches below diseased areas. Remove pruned material from the area and destroy it to prevent reinfection.
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