Gail Ruhl, Interim P&PDL Director, Senior Diagnostician, Dept. of Botany and Plant Pathology, Purdue University
We have received numerous phone calls and samples questioning the dieback
of the new growth on spruce trees as well as shoot dieback, blackening,
shredding and scorching of foliage on various deciduous trees. The symptoms
appear to be primarily on the west or windward side of trees. This type
of uniform pattern appearance is suggestive of an abiotic (noninfectious)
problem, such as might occur from environmental or chemical injury. Salt
injury has been ruled out due to the recent timing of symptom development
and non proximity of the trees and shrubs to sidewalks or roads. The most
likely ‘culprits’ responsible for the symptoms observed on
new tender plant growth are either excessive desiccation from recent severe
winds or the delayed symptom expression of frost damage that may have
occurred on April 23rd. Some of the leaf scorch observed may also possibly
have been caused by windy and hot conditions (over 80 degrees) in early
May when the leaves were developing.
If similar symptoms appear more randomly on the foliage of maple, ash, oak,
walnut and sycamore, then a fungal disease known as anthracnose, may be responsible
for the leaf blight. This fungal disease can cause darkened, necrotic areas
on leaves, particularly in the lower canopy, following wet, springtime conditions.
Another typical symptom of anthracnose on sycamores is the dieback of new shoots.
There is no need to spray anything on established trees for any of these problems.
In order to prevent further stress to the trees this summer, maintain good
cultural practices.
Click on the small image to view a larger image.
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Noninfectious leaf scorch |
Drooping candles (new growth) |
Noninfectious
leaf scorch on ash
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| Photos courtesy of Greg Bossaer |
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Drooping candles (new
growth)
due to environmental injury |
Close-up of drooping candles
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Photos courtesy of Doug Akers
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