What is Fire Blight Tree Disease?

Fire blight is a hard to control disease of fruit trees like pear and apple. It is caused by bacteria, its effects are devastating and it leaves a behind a burnt appearance; this is where it gets its name from. In addition to fruit trees, it attacks ornamental plants like roses, cotoneaster crabapple, loquat, hawthorn, pyracantha, and mountain ash. Unlike dieback, fire blight attacks flowers first, twigs next and finally branches.

Signs of this Disease

The first signs of fire blight usually appear in early spring, when the weather is humid and rainy and when temperatures rise above sixty degrees. Flowers infected by the disease turn black and die. The disease moves through the branch, infecting and killing young twigs. These dead twigs go black and curl over like a shepherd’s hook.” Affected branches look fire scorched as their leaves are black and wilted. Cankers, which are slightly sunken areas show up on the branches and the trunk. Fire blight affects many parts of the plant including leaves, stems, fruits and blossoms. In wet spring weather, a translucent milk-like, sticky liquid that contains multitudes of bacteria oozes out of the infected part of plant.

Fire blight spreads effortlessly in a lot of different ways and through different means, they include:

• Insects, birds, and animals transmit it from one plant to another.
• Rain drops splashes the bacteria among plants.
• Plants make contact all the time, that way the bacteria can move from an infected plant to an uninfected plant.
• Gardening tools can transmit the disease when gardening or even when watering. Tools should be sterilized after use on an infected plant.

Late spring or early summer is the maximum time of risk of infection. At this time, the bacterial emerges from its dormant period and the cankers become more pronounced. Infected branches should never be left on the ground when pruned, they should be immediately burnt or put in a bin as placing them on the ground could infect the surrounding bushes or trees.

Commonly Affected Plants

In your home garden, fire blight can be very damaging to pear and apple trees especially pear trees as they are very susceptible. Some pear trees, (e.g. Bradford) are unaffected by the disease but can develop it when the environment is advantageous to disease development. Some plants in the rose family such as the Rosacea, can be infected with fire blight, others include; mountain ash, photinia, crabapple, hawthorn, loquat, pyracantha, spirea, cotoneaster and quince.

Prevention & Treatment

Fire blight has no cure thereby making prevention very important. Though there are many ways to control fire blight, these methods are not 100% effective. Some fire blight control methods include; making use of recommended sanitation measures and cultural practices, choosing tolerant varieties, and applying bactericides and insecticides.

Bactericides & Insecticides: Bacteria enters plants through fresh wounds, blossoms or natural openings, it is then spread by rain and insects such as ants, bees, aphids, beetles and flies who transfer the bacteria to blossoms. Insect control can decrease the spread of bacteria, however, insecticides shouldn’t be used when plants are blooming. To learn more about disease and pest prevention oils, visit: 72tree.com/using-dormant-horticultural-oil-treat-tree-insect-infestations/

Sanitation Measures & Cultural Practices: all infected plant parts should be removed and destroyed, and all pruning tools should be disinfected with household bleach and water (one part bleach and nine parts water). This will lead to a reduction in the spread of the disease. Cuts should be made at least 8 to 12 inches beneath the infected tissue.

Pears: Pear trees can be treated with a copper fungicide spray (pre-bloom) and a streptomycin spray in bloom. The first spray should be applied immediately the flowers open and should be repeated every three to four days. There should be a minimum of fifty days between the application of streptomycin and harvesting of fruits.

Apples: If fire blight was severe the year before, then copper fungicide should be sprayed just before bloom. All branches and spurs should be thoroughly covered with streptomycin spray which is the recommended bactericide for apple trees in bloom. It should be sprayed first at the beginning of bloom and should be repeated every three to four daysas long as there are flowers.

Crabapple: copper fungicides are also used to treat crabapple trees. In other to lessen bacterial inoculum on the exterior of twigs and spurs, they should be applied before and after bloom. It shouldn’t be applied when plants are blooming as it may cause fruit abortion or russeting on the plant.

Arborists Discuss Controlling Tree Disease

Scheduling an annual inspection of your landscape is another way to prevent and treat tree disease. When you detect that something has gone awry with your trees and plants, contact your local tree professional. Properly identifying and treating the issue is key to halting it and preventing future occurrences.

Sources:
http://www.clemson.edu/extension/hgic/pests/plant_pests/veg_fruit/hgic2208.html
https://www.extension.purdue.edu/extmedia/BP/BP-30-W.pdf