Pruning Fruit Trees with Fire Blight in Brea: Best Practices

Understanding Fire Blight in Brea’s Climate

The fire blight pathogen thrives in environments that have temperatures above 65 degrees Fahrenheit and have experienced some level of moisture from rainfall, irrigation, or morning dew — both of which are quite typical in Brea’s Mediterranean-type climate. The first signs of fire blight usually emerge in late March/early April, at which time the disease will cause the flowers, shoots, and branches of affected trees to die, and they will exhibit the telltale “burned” appearance that has given fire blight its name.

Fruit trees such as apple and pear, along with many ornamental trees (including pyracantha and cotoneaster), are found throughout Brea, in areas that range from the hillside communities adjacent to Olinda Oil Museum to the residential areas surrounding City Hall Park. Therefore, it is imperative that tree owners within Brea understand how to properly prune their trees to protect them from fire blight damage.

Recognizing Fire Blight Symptoms

A key component of successful fire blight management is identifying and diagnosing the disease. Early symptom recognition through regular visual inspections of trees is essential to managing fire blight effectively. The initial symptoms of fire blight include wilted and blackened flowers that remain attached to branches. As the disease progresses, infected shoot tips begin to exhibit a “shepherd’s crook” appearance, characterized by the tip of the shoot curving downward.

Infected shoots will eventually develop dark brown to black discoloration, with the leaves remaining attached well into winter. Amber-colored bacterial ooze may also be present on infected tissues, especially in warmer, more humid weather conditions that are commonly seen in Brea during the spring and early summer months.

Cankers will develop on larger branches and trunks of trees exhibiting fire blight, and they will appear as sunken, discolored areas that have distinct margins between the diseased and healthy tissues. These cankers represent the primary location of bacterial overwintering; therefore, locating and removing cankers is an integral part of fire blight management.

Best Time to Prune Trees Affected by Fire Blight

Trees that are being pruned to remove fire blight infections should be pruned during the winter months when trees are dormant, and the bacteria associated with fire blight are inactive. For example, in Brea, the optimal time for pruning fire blight-affected trees is between December and February when trees are dormant, and the bacteria are not multiplying. Homeowners in areas adjacent to Brea Mall or Arovista Park can safely prune infected tissue without worrying about spreading the disease.

Tree pruning during dormancy also eliminates the need for sterilizing tools since bacteria do not grow at temperatures less than 45 degrees Fahrenheit. By pruning during dormancy, homeowners can thoroughly inspect and remove all of the infected material prior to the onset of spring growth and the resumption of bacterial activity.

However, there are times when pruning of active fire blight infections must occur in the summer. This situation requires prompt action to contain the spread of the disease, and it should be done under dry conditions. Never prune trees that are wet from rain, irrigation, or morning dew.

Proper Cutting Techniques and Distances

There are several research-based best management practices that describe the proper methods for pruning trees that have been affected by fire blight. To start, cut 12 to 18 inches below the last visible sign of browning or discoloration into healthy, two-year-old wood. This cutting technique removes the majority of the bacterial cells that may have moved systemically past the last visible sign of infection, and preserves the greatest amount of healthy tissue possible.

When dealing with smaller branches and shoots, make clean cuts at least 8 inches below the last visible sign of browning or discoloration. Larger limbs and trunks can be pruned back to healthy tissue that exhibits no discoloration in the inner bark or wood.

Regardless of the size of the limb, all cuts should be made at proper pruning angles just outside of the branch collar, and should be designed to allow for proper healing and to prevent water retention. All stubs should be avoided, as they create an entrance point for secondary infections and decay organisms.

Sterilizing Tools and Maintaining Good Sanitation

Once the growing season commences and the bacteria are actively multiplying, all cutting tools should be sterilized between each cut to prevent the potential spread of the disease. A 10% bleach solution can be prepared by mixing one part of household bleach with nine parts of water, and adding a few drops of liquid soap to improve adhesion. Alternatively, 70% isopropyl alcohol, or commercial disinfectants like Lysol, applied full strength, can be used to sanitize tools.

Dip or spray the cutting surface of the tool after each cut and allow a minimum of one minute of contact time for adequate sanitizing. Research suggests that during the dormant season, when cuts are made at the proper distances below infections, sterilizing tools may not be necessary. However, maintaining good sanitation practices adds another layer of protection to prevent the spread of the disease.

Removing Debris and Disposing of It Properly

It is essential to remove all of the infected plant material from the premises immediately after pruning. Fire blight bacteria can survive in the infected plant material and create a source of reinfection under ideal weather conditions.

The infected material should either be burned under local fire restrictions or sealed in plastic bags for disposal with normal household waste. Under no circumstances should fire blight-infected material be composted. Composting is unable to achieve high enough temperatures to kill the bacteria associated with fire blight.

Residents living in areas with a wildland interface to Chino Hills State Park or other similar areas should be extremely cautious regarding disposing of the debris to avoid spreading the infection to the native vegetation and neighboring properties.

Management of Infected Trees with Structural Damage

In cases where fire blight infections have damaged the major structural branches or trunk of a tree, property owners are faced with difficult decisions regarding aggressive pruning versus tree removal. Major limbs or trunks that have been girdled by canker development will ultimately lead to tree mortality regardless of treatment.

Homeowners of valuable mature trees in established neighborhoods around the Brea Museum & Heritage Center or historic areas near the Curtis Theater will benefit greatly from consulting certified arborists to assist in determining if aggressive pruning can save the tree, or if removal will be the most practical option.

Young trees that have developed extensive fire blight infections, especially those grown on susceptible rootstocks, may require total tree removal to prevent the disease from spreading to nearby healthy trees and to protect the overall value of the landscape.

Preventing Disease through Proper Cultural Practices

In addition to providing fire blight removal and control services, our certified arborists will also educate you on cultural practices that can help to reduce the occurrence of fire blight in the future. One of the biggest mistakes that people make when growing trees is providing them with excessive nitrogen fertilizer that causes succulent growth that is highly susceptible to infection by the fire blight bacterium.

Another way to prevent fire blight is to prune your trees every year during dormancy to create an open canopy that will allow for good air movement and rapid evaporation of excess moisture from the leaves following rain or irrigation. Suckers and water sprouts should also be removed since they can act as pathways for the fire blight bacterium to infect the tree.

If you have automatic irrigation systems installed in your lawn, please modify the schedule and spray pattern to minimize direct contact of the spray with the leaves of the trees, especially during warm weather when the rate of bacterial multiplication increases dramatically.

Choosing Disease-Resistant Varieties

When planting new trees or replacing trees that have been damaged by fire blight, choose disease-resistant varieties whenever possible. Some apple varieties, such as Enterprise, Freedom, and Liberty, exhibit good resistance to fire blight. There are also some pear varieties that exhibit greater resistance to fire blight than others. Local nurseries in the Brea area will be able to provide information on which varieties of trees are best for use in Southern California and provide improved resistance to fire blight.

Consulting with local extension services and/or certified arborists will assist you in selecting the correct varieties based on the site conditions.

Hiring a Professional Tree Pruning Service

Many complex fire blight problems require professional assistance to properly diagnose, treat, and prevent further disease spread. Certified arborists have access to the latest research-based management techniques and the equipment required to safely and effectively treat the problem. Professionals become even more important when dealing with large mature trees, multiple trees that are infected, and/or when fire blight threatens valuable landscape investments located in established Brea neighborhoods such as Memory Garden Memorial Park.

Our Approach to Fire Blight Management

At Brea Tree Services & Arbor Care, we understand the severe threat fire blight presents to Brea’s fruit trees and ornamental landscapes. Our certified arborists continually review and update their knowledge base regarding fire blight management to ensure that we are utilizing the most effective tree pruning techniques currently available.

Our company offers comprehensive fire blight services that include the accurate diagnosis of fire blight, research-based pruning protocols, and continued monitoring to prevent the re-infection of the trees. Our systemic approach includes proper cutting techniques, good sanitation practices, and the proper timing to provide the highest probability of successful treatment while minimizing harm to the trees.

Our certified arborists will conduct a detailed assessment of the infected trees to explain treatment options and long-term management plans for the trees. They will also assist you in determining whether aggressive pruning can salvage the tree or if tree removal will be the best course of action.

Please contact us today for expert fire blight diagnosis and treatment. Our experience in tree pruning and disease management enables us to protect your landscaping investment while preventing the spread of this significant bacterial disease to neighboring properties within the Brea community.