Over the last three years we have been getting an alarming number of reports of limbs dying in shrubs and trees. Hollies, cherry laurels, magnolias and other shrubs are exhibiting dying branches. Maples and redbuds are also being affected. Occasional dying branches are not unusual. However the level of damage we are seeing is concerning.

What kills limbs in shrubs and trees? Water moves through plants in specialized cells just under the bark. Anything that kills these cells cuts the water supply to a stem causing the limb to die. Any physical restriction such as an object wrapped around a stem can eventually girdle stems. Chewing by animals or insects and even woodpecker damage can also girdle stems.

Likewise, fungal infections can create infected wounds that cut off the flow of water in stems killing the affected stems. Fungi can infect cracked stems that result from environmental extremes such as severe cold or high winds. The swollen cracked area on stems results from a fungal infection is called a ‘canker’. 

'Pink disease' - Bartlett Tree Experts in Brevard, NC was first to note that a 'pink disease' (likely referring to Erythricium salmonicola) was causing cankers in trees and shrubs. Since the first diagnosis in Brevard in 2022 the fungus has spread to Henderson County. We are seeing the fungus in cherry laurels, hollies, magnolias and other landscape trees and shrubs. 'Pink disease' is characterized by a crusty pink fungus on dead cracking limbs. The damage will be noticeable as dead branches in the the plants.

What can you do? The first step in pest management is to try keeping plants as healthy as possible through proper fertility and irrigation. Avoid planting plants too close together or too deep. Healthy plants are better able to resist disease.

Next, inspect any dying limbs of trees and shrubs. Look for swollen and cracked stems and sap exudation indicating the presence of a canker. Inspect the stem for sign of fungus. 'Pink disease' will often be characterized a white mycelial mat that eventually turns into a salmon pink color. If you see a flagging or dying branch, prune the limb below the canker. Sanitize pruning equipment between cuts with a 10% solution of Lysol or Pine Sol. Dispose of the infected branches off site or burn them.

Since 'Pink disease' is a new organism in our area, no research has been done to test fungicide treatments for landscapes in WNC. Research has shown Bordeaux mixture (lime/sulfur) can help protect trees. Growers can also try a rotation of fungicides such as Mancozeb and Phyton copper, or Cleary’s 3336 and Banner Max to protect plants. In the past these combinations have been effective preventing other fungal pathogens.