AUBURN UNIVERSITY, Ala. – There are some things that may be sweet as a peach but seeing a peach crop affected by twig dieback is not one of them. There are various plant diseases that can cause the twigs, branches and shoots of a peach tree to die. Alabama Cooperative Extension System Plant Pathologist Ed Sikora offers information about what causes twig dieback, its symptoms and how to manage the disorder in peach trees.
Twig dieback is often the result of one of two diseases: bacterial blight or blossom blight. According to Sikora, these two common plant diseases are active every spring. Bacterial blight, often referred to as bacterial twig blight or dieback, is a bacterial disease that can cause dieback of twigs. Also known as brown rot, blossom blight –caused by a fungal pathogen– is a fruit tree disease that can also cause twig dieback in the spring, as well as fruit rot later in the season.
Sikora said it is difficult to determine which disease is present by symptoms alone.
“Symptoms of both diseases can appear early in the spring as the collapse of flowers,” Sikora said. “Flowers can turn brown and a gummy ooze exuded from the bark of infected trees, causing the dead flowers to stick to the twigs.”
Infected leaves can dry up and cling to their sticky branches. Cankers can also develop at the base of the leaf buds and flowers. Especially in the spring, gummy sap can often be found exuding from these cankers.
During wet weather, brown-to gray spores of blossom blight can appear on dead flowers, indicating the fungal disease is the cause and not bacterial blight. If these spores are lacking, however, the Auburn University plant diagnostic lab can confirm which disease is the culprit.
According to Sikora, trees that are growing under stressful conditions are more susceptible to both of these diseases.
Weather conditions often dictate the prevalence of these diseases. If weather is cool and wet, bacterial blight thrives. Blossom blight is more common with warm, moist weather.
Removing infected twigs from infected trees is the first step in management of twig dieback. Sikora advises pruning out affected tissue during dry weather to avoid the spread of bacterial blight, blossom blight or other pathogens. Disinfecting pruners between trees is also critical in stopping this spread. To properly do this, soak the pruners in a 70 percent alcohol solution or a 10 percent bleach solution.
Later in the season, untreated blossom blight can lead to fruit rot, also known as brown rot. Once this occurs, it is crucial to remove and destroy all the affected fruit from the ground to reduce the spread of the pathogen.
“If affected fruit remains on the ground, fungal spores produced on the fruit surface can spread to healthy fruit in the tree,” Sikora said.
Brown rot can continue post harvest and spread among recently picked fruit. This can make for a frightful basket of peaches for the whole family.
For more information on protecting peach trees from twig dieback, see the Alabama Extension content piece Causes of Twig Dieback in Peach Trees at www.aces.edu. People can also contact the Extension commercial horticulture agent that serves their area.