Fire blight is a devastating bacterial disease that can infect flowers, current year shoots, and the rootstock of apple trees. Other trees and shrubs that can contract fire blight includes pear, quince, cotoneaster, hawthorn, serviceberry, and crabapple. Unfortunately, this spring’s wet, cool weather has been conducive to fire blight; which is caused by a bacterium (Erwinia amylovora). It can spread quickly when environmental conditions are right for disease development.

Flower blossoms or wounds are entry points the bacteria use to get into the plant. Any blossom will continue to be susceptible to fire blight as long as it has intact petals. Wounds can be inflicted by man but also wind or hail The infected flowers or leaves turn black and then die. As the bacteria moves down the branch, young twigs blacken and curl. The leaves will wilt and blacken as well, but they remain on the branch. This gives the plant a fire-scorched appearance. Sometimes this is described as looking like a shepherd’s hook. Cankers appear on the branches and the main stem. The disease can be spread from plant to plant by insects and rain. Sadly, there is no cure for fire blight. The old saying “An ounce of prevention is worth a pound of cure,” definitely applies here.

There are varieties that are less susceptible to fire blight. Choose these when possible. Avoid excessive nitrogen applications that promote new plant growth that is susceptible to disease. An early spring preventive spray with streptomycin or copper-based fungicides may be necessary for commercial orchard settings.

In general, the cost and effort are not feasible fore most homeowners. Trees need to be sprayed at a 3-4 day interval during bloom and the entire leaf canopy must be treated for control. Most homeowners help reduce the spread of the disease by implementing good sanitation practices. All affected plant parts should be removed and destroyed. If infected plant parts are not removed from the site, there is a great possibility that the bacterium can reinfect the tree or infect other susceptible trees nearby. Wait to prune until the window for disease development is past. It is best to prune on the driest and coolest day possible during the summer or during the winter dormant season. All blighted shoots should be pruned into last year’s growth, or at least 12 inches below the last visible sign of necrosis which causes leaves, stems and other parts to darken and wilt. Sanitize pruning shears between each cut. Pruners can be dipped into a 10 percent household bleach or Lysol to reduce the risk of transmitting the disease. If the cankers are left on the tree, they will continue to spread each season.