Fighting Fireblight

Have you noticed the blooms, leaves, and branches of your pear and apple trees wilting and turning black? Are there slightly sunken areas on the branches and main stem? If so, your trees may have been infected with one of the most devastating diseases of apples and pears. Additionally, this bacterial disease will not be easy to control. You are fighting Fireblight (Erwinia amylovor).

Fireblight symptoms appear in the spring when temperatures begin to warm. Flowers are usually affected first and will start to wilt and turn black. As the disease moves to leaves and stems, the leaves will wilt and turn black. Blackened leaves remain on the branch in a “shepherd’s crook” form, giving the infected branches a fire scorched appearance, hence the name. Branches will have cankers, and in wet weather you may notice a sticky, milky-type liquid may oozin from infected plant parts.

While pear and apple are the the most commonly infected plants, other members of the Rosaceae family such as hawthorn, photinia, and spirea can also be affected by fireblight. Insects and wind spread the pathogen.

There is no cure for fireblight, thus PREVENTION is essential. To help reduce disease severity use resistant plant varieties, cultural and sanitation methods, and apply insecticides and bactericides.

Select cultivars of pears and apples that are fireblight resistant. Resistant pear varieties include ‘Bradford’, ‘Whitehouse’, and ‘Capital.’ ‘Bradford’ is considered the most resistant of those listed, but will develop the disease if conditions are right. ‘Red Delicious’, ‘Ozark Gold’, and ‘Liberty’ are some resistant apple varieties.

Since insects spread the disease, controlling insects could help prevent the spread of fireblight. However, these insecticides should not be used during bloom. Contact your local Extension office for insecticide recommendations.

Streptomycin is the bactericide recommended for fireblight control in susceptible apple and pear trees. Use streptomycin as a preventative treatment only, and spray soon after bloom when insects or mechanical practices injure tender shoots, making them more susceptible to contracting fireblight. In pears, repeat the streptomycin application at at four-to-seven day intervals as long as blooms are present. Streptomycin must be sprayed a minimum of 50 days before fruit harvest. Always apply insecticides according to label directions. These control methods are most effective for younger trees, when adequate foliage coverage can be achieved.

Cultural and sanitation methods are also important for fireblight prevention. During spring and summer, prune out infected branches 8 inches below the damage. Avoid pruning when the plants are wet. Dip pruning tools in 70 percent isopropyl alcohol (rubbing alcohol) or 10 percent bleach solution (1 part bleach to 9 parts water solution) between each cut. Wash and oil shears when you are finished. These practices avoid spreading the pathogen.
Avoid heavy nitrogen fertilization, especially in summer, when succulent growth is most susceptible to fireblight infection. Avoid splashing water.
For more information on the identification, control, and prevention of fireblight, contact your local Extension office.

Ellen Huckabay is the Outreach Coordinator for the ACES Home Grounds, Gardens, and Home Pests Priority Team. She can be reached by email at knighec@auburn.edu or by phone at 334.844.3021.