fungus on trees and azaleas - Ask Extension
I have large azaleas that are dying back one large branch at a time. It began a few years ago. There is fungus on the branches of the azaleas and ot...
Knowledgebase
fungus on trees and azaleas #872552
Asked June 11, 2024, 8:51 AM EDT
I have large azaleas that are dying back one large branch at a time. It began a few years ago. There is fungus on the branches of the azaleas and other trees in the yard, including dogwoods. What cane be done to help the shrubs and trees?
Baltimore County Maryland
Expert Response
The growths pictured on the branches are not a fungus (exactly), but are lichen. (Lichen are unique organisms that involve a fungus living with algae inside of it, but the fungus part does not infect plants.) They are harmless and only present because the bark they attach to is getting enough light and rain (from the azalea's loss of leaves). They often grow on tree trunks, and do not need removal. Abundant lichen might actually indicate decent air quality, since few are tolerant of heavy air pollution.
The azalea branch dieback is hard to diagnose once it's this advanced. Several issues can affect azaleas and their rhododendron cousins, including drought stress, growing in too much direct sun, and poor soil drainage or root flooding from over-watering. Dead or dying branches are best pruned off as soon as they're noticed, so they don't harbor a problem that might spread. Wood-boring insects, while uncommon in azaleas, tend to target plants under stress (like from heat or drought), as do a couple types of opportunistic fungi. (These fungi do not produce visible mushrooms or other growth, they only kill the interior of the branch wood, causing the foliage to dry out and turn brown.)
There is no cure for any existing disease, but if the plant's roots are healthy, you can drastically cut back all branches (to perhaps within a food of the ground, more or less), which will trigger regrowth. This process of rejuvenation will be slow, with regrowth taking a few years to regain the size the plant used to be, and to begin flowering again. Any azaleas with too many leafless branches and very little foliage should be replaced instead, as they are probably too weak to be able to bounce back.
If you can share photos of the overall azalea shrub(s) -- how they look and where they're growing -- we can see if there are any obvious sources of stress, but otherwise any symptoms on trees that are in decline are probably unrelated (outside of a widespread issue like drought), and we would need to see images of their symptoms to try to make a diagnosis.
Miri
The azalea branch dieback is hard to diagnose once it's this advanced. Several issues can affect azaleas and their rhododendron cousins, including drought stress, growing in too much direct sun, and poor soil drainage or root flooding from over-watering. Dead or dying branches are best pruned off as soon as they're noticed, so they don't harbor a problem that might spread. Wood-boring insects, while uncommon in azaleas, tend to target plants under stress (like from heat or drought), as do a couple types of opportunistic fungi. (These fungi do not produce visible mushrooms or other growth, they only kill the interior of the branch wood, causing the foliage to dry out and turn brown.)
There is no cure for any existing disease, but if the plant's roots are healthy, you can drastically cut back all branches (to perhaps within a food of the ground, more or less), which will trigger regrowth. This process of rejuvenation will be slow, with regrowth taking a few years to regain the size the plant used to be, and to begin flowering again. Any azaleas with too many leafless branches and very little foliage should be replaced instead, as they are probably too weak to be able to bounce back.
If you can share photos of the overall azalea shrub(s) -- how they look and where they're growing -- we can see if there are any obvious sources of stress, but otherwise any symptoms on trees that are in decline are probably unrelated (outside of a widespread issue like drought), and we would need to see images of their symptoms to try to make a diagnosis.
Miri
