ILLUSTRATIONS OF TREE
DISEASES
FOLIAGE DISEASES OF DECIDUOUS TREES
- 1.
THIS IS PAGE 1 OF 3.
This page shows types of
symptoms which appear on leaves.
A typical example of each is presented. There are 12 pictures; scroll
down the page to see them all.
|
\
|
SYMPTOMS of FOLIAGE
DISEASES
|
|
A
|
|
|
POWDERY
MILDEW
is one the most easily recognized leaf diseases.
The white patches are the growth of causal
fungus and give the disease its common name, as
here on a leaf of Populus.
|
|
|
APPLE SCAB
is another leaf disease caused by a fungus
which grows on the leaf surface. The dark
patches are very evident on the underside of
these apple (Malus) leaves.
Photo courtesy of Vernyl
D. Pederson
|
|
|
A closer view of a leaf with Apple
Scab shows the dark sooty surface of the
infections.
Photo courtesy of H. A.
Lamey
|
|
|
LEAF RUST.
Some leaf infecting fungi cause very conspicuous
symptoms. The bright orange spots on these
Saskatoon berry (Amelanchier) leaves are
caused by a Rust fungus,
Gymnosporangium nidus-avis.
|
|
|
LEAF SPOT.
Many parasitic fungi cause discrete infections
of limited size. On these sugar maple
(Acer) leaves, each small circular
Leaf Spot results from a separate
infection by the fungus Phyllosticta .
|
|
|
SUMMER LEAF SCORCH,
on a basswood (Tilia ) leaf. This is
a disorder caused by water stress. Symptoms
caused by abiotic (nonliving) agents often
appear in distinct patterns, in contrast to the
more or less random distribution of infections
by leafspot pathogens. Compare the distinct
pattern on this leaf to the leaves in the other
pictures.
|
|
|
LEAF BLIGHT.
In some diseases, the individual leaf spots may
COALESCE or spread together. This has happened
on these green ash (Fraxinus) leaves with
Mycosphaerella blight.
|
|
|
LEAF BLOTCH.
Some leaf infecting fungi are not limited to
discrete spots but can spread extensively in the
leaf, causing necrotic blotches. The Leaf
Blotch of horse chestnut, caused by
Guignardia aesculi, is such a disease.
|
|
|
In LEAF SPOT caused by
Cercospora on evergreen privet
(Ligustrum), the lesions enlarge
periodically during favorable weather. The
traces of earlier lesion margins appear as dark
concentric rings in the lesions.
|
|
|
LEAF DISTORTION.
Infections which occur while leaves are
expanding can produce distortion.
These necrotic areas are caused by
ANTHRACNOSE on green ash
(Fraxinus). The adjacent living tissue is
misshapen.
Photo courtesy of Vernyl
D. Pederson
|
|
|
LEAF DISTORTION
Infections which occur while leaves are
expanding can produce distortion.
The genus Taphrina is particularly noted
for this type of infection. This is LEAF
BLISTER on chokecherry (Prunus).
|
|
|
LEAF DISTORTION
Infections which occur while leaves are
expanding can produce distortion.
This distortion is caused by infection by
DOWNY MILDEW on Grape (Vitis).
Photo courtesy of Vernyl
D. Pederson
|
|
|
.
|
© RWS 8 June'99
|
GO BACK TO TOP OF THIS
PAGE?
CONTINUE WITH FOLIAGE DISEASES OF HARDWOODS? YES.
. NO, RETURN
TO GUIDE PAGE?
These images are provided for the personal use of students, scholars,
and the public.
Any commercial use or publication of them is strictly prohibited.
The images included in these collections were scanned from slides
used by Professor R. W. Stack in his course, Tree Diseases (PltPath
456), at North Dakota State University. All of the images are
original photographs, mostly taken by Prof. Stack. A few pictures are
borrowed and are included here by permission and with
acknowledgement. The images are organized according to the course
syllabus.
The images were scanned and processed by the author at the Multimedia
Resource Center, North Dakota State University, Fargo, ND 58105.
Prepared by Robert W. Stack
NORTH DAKOTA STATE UNIVERSITY
Original 25 Sept 96, this version 8 June 1999. Revised 30 April
2001
TO COMMENT: rstack@ndsuext.nodak.edu