AMF1-1
Two diseased leaves from a "sick looking" branch near the base of the plant.
This branch had some spotted leaves, as shown above, where the left is a leaf bottom and the right is a leaf top.
A microscopic inspection of the leaf showed nothing unusual except for the dark discolorations, which
may simply be a secondary pathogen that is taking advantage of the weakened plant.
AMF1-2
Branch junction destruction in a Mountain Fire Andromeda.
Since the outer leaf junction looked suspicious, I clipped it off and scanned it at 2400 dpi.
The result is shown in the picture above.
The wrinkled and dead bark seem to indicate that this
bush is under a strong attack by some pathogen.
AMF1-3a
AMF1-3b
AMF1-3c
Examining this diseased branch junction using a 400x microscope, I found spores, as shown above.
These are the same type of spores found on the other diseased trees.
Phytophthora are known to shoot out transparent tendrils,
and the rightmost picture above shows such a tendril clump.
In particular, note the yellow spore suspended in the air!
This bush was near our garage entrance. It appeared very healthy but had one sick looking branch near the base.
H1-1
Here the inner bark is almost completely eaten away by white canker.
(400x)
H1-2
Here the inner bark has lots of light gray white canker in it. It is far from
uniform in consistency. (400x)
↓
H1-3
Part of the inner bark has been destroyed, leaving an air gap. Canker is also
growing on the surface of the outer bark. And hyphae are snaking around the
surface. Note the characteristic dark brown "eye" of the lower one. (400x)
H1-4
The blobs of white canker have a higher density where the bark is pushed out.
At that point there are also some yellow blobs on the bark's surface. (400x)
H1-5
The higher density of the white canker blobs at the base of the inner bark is
reflected in the white canker above it on the surface of the outer bark, which is pushed out. (400x)
H1-6
There weren't that many areas with many spores on the outside bark, but this one was one of them.
But these spores looked fairly old, and some appeared broken.
(400x)
←
H1-7
Two spores in the lower-left are associated with hyphae.
The hypha on the right is long, with a characteristic brown "eye" (red arrow). (400x)
H1-8
The razor cut of the leaf began here.
Note the two long hypha - one is emerging from the black area.
The one above it emerges from the leaf edge.
Both are long and go far to the right under the leaf surface.
They are hard to see because they are semi-transparent. (400x)
↓
H1-9
The young yellow spore on top (red arrow) is probably related to the canker on the other side of the leaf.
The vertical hypha is almost certainly canker related.
The two horizontal semi-buried tubes may or may not be canker related (they could be leaf veins). (400x)
H1-10
The gray-white blobs within this leaf are almost certainly white canker.
But the white diffuse blob may be a leaf vein.
The canker blobs seem to like being near a vein - a source of nutrients. (400x)
This shrub, growing in our front yard, almost died from White Canker a few years
ago. Fungal sprays saved it. It had also been sprayed about a month before these
pictures were taken. Therefore, I didn't expect to see too much evidence of
white canker.
L1-1
Healthy lilac twig surface at 400x. There is only one young yellow spore present.
Note the blue 50μm blue scale bar above it.
L1-2
Healthy lilac leaf bottom at 400x. There are no imperfections to note.
L1-3
Healthy lilac leaf top at 400x. This leaf and the one in L1-2 were very flat
and a deep green in color, and simply looked healthy.
L1-4
→
←
Cross-section of a twig having diseased leaves (400x).The black arrow shows normal heartwood. The red arrow shows the center of a white canker growth that is spreading
into the heartwood.
L1-5
The bottom of a diseased leaf (400x), showing a white canker growing within the
leaf. There is a spore almost in the center of the canker, directly above the the 50 μm
scale bar.
L1-6
The top of a diseased leaf (400x), showing an abundance of hyphae, and lots of yellow objects which look like spores.
There is also a curious black object.
L1-7
A close-up of a very diseased surface of twig bark. It looks like a debris
junkyard. (400x)
L1-8
I found this strange object on the surface of diseased twig bark.
The translucent filaments seem to radiate from the object. This same type of object
is often found on other trees infected with white canker. (400x - 50μm scale
bar)
L1-9
This oval translucent white object is actually a tiny insect! I caught it crawling
around, presumably foraging for food. The 50 μm blue scale bar shows how tiny it
is!
L1-10
The white canker material is fairly diffuse within the sapwood. Here a ray of it
extends down into the bark. The "frothy" material at the far top is the pith of
this twig, which is about 1/8 inch in diameter. (400x)
L1-11
Here the inner bark is a cleaner, but there is more white canker debris on the
outside of the bark. (400x)
L1-12
A leaf cross-section showing a young spore growing out of the bottom of the
leaf. Note the bulge of the leaf at this point, which is apparently due to the
spore's buried supporting "root" structure. Also, most of the canker seems to be
associated with the leaf bottom. (400x)
L1-13
Not only has canker material infused the lower part of the leaf here, but a
spore and hypha are also growing inside the leaf. The upper part of this leaf
here has pretty much been destroyed. (400x)
L1-14
While slicing the leaf with a razor to obtain this cross-cut, a portion of leaf
tissue containing 4 buried spores was partially torn off the top surface. (400x)
L1-15
This leaf cross-section exposed a patch of white canker hiding right in the
middle of the leaf, causing a slight bulge of both surfaces. Note the long hypha
in the foreground looping around this canker. (400x)
L1-16
Here we see a leaf cross-section that has an extensive amount of white canker
material growing on it. (400x)
White Canker on lilac leaves shows itself as leaves that are appear very dry, dull,
and cupped - as if starving for water. Eventually these leaves curl up, turn black,
and die. For comparison, here is a microscopic picture of a twig stem and both sides
of a leaf.
In contrast to the above, I found another lilac leaf that was somewhat wrinkled and gray,
but without insect damage. As you can see in the following picture set,
the microscopic views are far different!
With all this infection taking place, the bark has a hard time maintaining itself,
and lots of disease organisms move in to take advantage of the situation,
as shown in the following pictures.
ML1-1
Note the White canker spores visible on the twig's surface, where the bark had split.
(400x)
ML1-2
Here there are two spores and two hypha, both next to an area that appears to be
infected with white canker. (400x)
ML1-3
Note the white canker pieces and mangled bark, which also conatins white canker
(although it is more of a yellow-brown in color). (400x)
ML1-4
This twig cross-section shows a spore embedded in the bark, and two spores
nestled between the sapwood and bark. Traces of canker material are growing just
to the right of it. (400x)
ML1-5
Note the white canker in the sapwood gave rise to a hypha which grew a stalk that generated
another particle of white canker! (400x)
ML1-6
The bark here is really mangled due to white canker.
Note the hypha in the sapwood which connects to the blob of white canker
and also to the diffuse area of white canker within the bark.
(400x)
ML1-7
This is a leaf cross-cut perpendicular to the stem.
The white blob in the center is the center vein.
The surrounding gray blobs may be canker.
The small translucent blob on top is probably canker material. (400x)
↓
↓
↓
↑
↑
↓
ML1-8
In this leaf cross-cut, there is a light gray hypha (black arrows) connecting
three bits of white canker material (red arrows). Hypha semi-transparency makes
them hard to see. (400x)
ML1-9
While making this leaf cross-cut, a small piece of leaf surface was ripped up, exposing a canker spore.
This spore apparently had some pieces extending above the leaf surface. (400x)
This shrub, growing in our front yard, almost died from White Canker a few years
ago. Fungal sprays saved it. It had also been sprayed about a month before these
pictures were taken. Therefore, I didn't expect to see too much evidence of
white canker.
The leaves were generally free of white canker. The little that was present is
shown in the following pictures.
R1-1
The quarter-inch twig shown here was from the tip of a sick-looking rhododendron bush.
Look closely and you will see that this branch is simply loaded with spores!
In fact, it's one of the most prolific spore producers I've seen so far.
The spores seem to prefer year-old wood, and seem to take up residence everywhere along the branch.
The spore density on older wood decreases, probably because the bark there
is virtually falling off due to disease and no more nutrients are available for growth.
R1-2
←
←
↑
A 400x view showing three spores which appear to be in the act of reproducing.
The arrows show the yellow young spores coming out of the side of the white "mouth".
R1-3
←
This 400x view of the bark shows an area of abundant spores - young and mature.
The blue arrow points to a white "spider" object in the upper right.
R1-4
↑
A variety of spore-associated objects is shown in this 400x view of the bark.
Strangely, this view seems to show that the yellow young spores first emerge as green in color
and then evolve into a yellow color.
Also, the blue arrow points to a good view of the often difficult-to-see spore stalk on a newly-born spore.
R1-5
This is a diseased leaf taken from a 10 '' high rhododendron bush on the north side of our garage.
Most other leaves on the bush weren't this bad looking, although they all were somewhat puckered,
as if under attack by some pathogen. Pictures R1-1 through R1-9 were all taken
in mid-September 2008.
R1-6
The top side of the rhododendron leaf shown in picture R1-5.
The black areas are dead parts of the leaf.
Note the hyphae near the leaf surface.
They are often associated with these dead spots.
R1-7
The bottom side of the rhododendron leaf shown in picture R1-5.
The dark brown area is a dead part of the leaf.
There are what appear to be numerous dead/brown hyphae scattered around.
R1-8
Here is a cross-cut of a 1/4 inch twig from that rhododendron bush.
The cankerous material has consumed a large part of the inner bark. Note the
chunk of it sticking out.
This bush is on the north side of our garage and is now (early June, 2008) full of beautiful red blooms.
The leaves had looked healthy, but during the past week had begun to droop and look sick.
V1-1
To the left is a segment of a branch taken about 18" from the branch's tip.
It is loaded with spores.
In several areas it is so thick that it forms solid masses, making this bush a prolific infection agent!
V1-2
Another branch from this bush, again showing the spore density. As before, you can
see that the spore density is by far highest near the branch junctions.
V1-3
The spore density isn't as high here as in the other pictures. Nevertheless, it
again demonstrates the clustering of the spores around the branch junction.
V1-4
Still another branch showing the clustering of spores around the branch junction.
V1-5
Here we can see that the sapwood is infected, and has almost separated from the
heartwood. Furthermore, the bark has become almost totally replaced by white
canker material. (400x)
V1-6
The particles of white canker under the bark here are so numerous that they are
pushing the bark out. Careful examination seems to show that each particle
closely resembles a spore in shape. (400x)
V1-7
This is a rare picture, since it captures white canker material growing from the
phloem, through the dark green cortex, through the outer bark,
transforming into a hypha, and then ending as a young spore.
It ties together all of the infection structures. (400x)
V1-8
The lower-left portion of this photo shows a generally canker-free area under
the bark. However, as you move to the upper-right, canker density rapidly
increases, pushing out the bark slightly. If you look closely, you'll see that
the canker density on the outer bark follows the canker density under the bark. (400x)
V1-9
Finally, this portion of the bark is solidly infected with white canker, so much
so that air spaces have opened up under the bark (400x)
V1-10
Even infected viburnum leaf tops appear clean. I had to search a bit to find
this area with white canker particles. Note the "octopus" structure. They seem
to be associated with the white canker, but their shape is unlike objects seen
in other infected shrubs or trees. (400x)
V1-11
Unlike the relatively clean leaf tops, the leaf bottoms have plenty of these
octopus objects. Here are three of them close together. They each have about 8
"arms". (400x)
V1-12
This leaf cross-section explains why viburnum leaves never appear to be infected - the
infection generally resides deep inside the leaf, so can't be seen. The
infection does, however, cause a slight bulge in the leaf. (400x)
V1-13
This cross-section shows that the infection became so dense that it pushed out
through the bottom of the leaf. Not only that, but it appears to have caused an
octopus object to arise from the top of the leaf. The brown discoloration may be
because this canker cluser is dying. (400x)
V1-14
Another white canker particle cluster. While the focus is poor, you can make out
an octopus protrusion on the leaf bottom directly below this canker cluster. (400x)
V1-15
A good view of an octopus object that seems to be feeding off a canker buried
deep within the leaf. This is also a good view of the base of these objects.
This base is a more translucent gray, similar to some canker material. (400x)
This viburnum bush is about 8' tall. The branch shown in these pictures was
taken near the top, at the 6' level. This is the only bush or tree whose leaves
appear to not be affected by this disease. However, some of the stem bark looks
unhealthy, and several years ago there was a bleeding canker at the base of this
bush.
In summary, while white canker can severely affect a viburnum bush, the leaves will
not appear diseased since the white canker material hides deep within the leaf.
However, as with all infected trees and shrubs, the disease easily shows itself
when examining cross-sections of the twigs and leaves using a 400 power microscope.
B1-1
This is a close-up of a branch junction. The spores are in close proximity to it,
although the spore density doesn't appear to be very high.
B1-2
Here is a 400x close-up of the spores at that junction.
Many of these spores have that double-lobed appearance.
Also, many of the spores have a yellow substance between or adjacent to the lobes.
B1-3
This area also seems to contain many spores, but they are almost all small and yellow. (400x)
B1-4
Here we see a both spore types - white and yellow.
The two spores in the lower right are interesting because they appear joined and are the same size.
It makes you wonder if the yellow spores are generating the white spores, or vice versa. (400x)
B1-5
This 400x picture was included simply because it shows the white spores growing on a bark protrusion.
Unfortunately, the microscope's lack of a good depth of view prevented most of it from being in focus.
B1-6
Here is what a diseased leaf looks like, with typical white canker puckering (here
squashed flat by the flatbed scanner). The dead areas are usually at the edge of
the leaf, not at the leaf center as here.
B1-7
This leaftop picture gave me a surprise - I hadn't expected to see young/yellow spores
on the top of any leaf.
Yet, here they were (no spores were on the bottom).
Not only were they there, but almost the entire gamut of spore associated objects were also present!
This picture was taken in early June 2008. When I examined these leaf tops in
mid-September, there wasn't a single yellow spore present, and only a very few
white spores were present. Therefore, the spores were shed in the intervening
months. (400x)
←
←
←
←
Pith
B1-8
Check out the white canker under the inner bark (blue arrow). It matures into
light-gray blobs (red arrows). The black area is a void. The twig's pith is in
the upper-right corner and is a frothy white. (400x)
B1-9
Not only is the inner and outer bark riddled with white canker, but two hypha
are also sticking out of the bark. Note particularly the one on the left - it
has given birth to a white canker particle and a young yellow canker spore. This
combination is rarely seen. (400x)
B1-10
The sapwood and inner bark have white canker growth, and several particles of
white canker can be seen directly under the bulge in the bark. (400x)
B1-11
The white canker has grown quite a bit in the sapwood and inner bark, and is now
shooting out hyphae, which look like long icycle-like growths. These growths
seek out other areas to infect. (400x)
↓
B1-12
Snow white canker is consuming the sapwood, the inner bark is mostly all canker,
and you can see some white canker particles emerging from the outside of the
bark (red arrow). (400x)
B1-13
This is a leaf cross-section. Unlike twig cross-sections, it's more difficult to
see obvious signs of white canker in leaf cross-sections. Here we see a piece of
white canker growing up out of the leaf surface, and to the right a hypha
growing out of the surface. (400x)
B1-14
The bottom of this leaf seems to have a lot of diffuse white canker material,
and one piece of it is sticking up and almost piercing the top leaf surface,
making a slight bulge in it. (400x)
This vine grows on the south side of our house.
It has generally done well, but white canker took a heavy toll on it the past few years.
Some conclusions we can draw from these pictures:
- White canker yellow spores only appear in late spring/early summer
- White canker appears snow white when growing in the
sapwood and chokes off the vessels (pores) there
- White canker is light gray in color when growing within the inner and outer bark
- There are almost no mature white canker spores present in late summer (mid September)
- White canker is easier to detect in twig cross-sections than in leaf cross-sections
T1-1
This branch junction has relatively few spores near it.
T1-2
While white canker spores usually congregate at branch junctions, here the spores
are more numerous at this branche's midpoint - several inches higher on the branch.
The spores seem to gather on the veins of the branch.
T1-3
Here is a 400x close-up of some spores on an otherwise featureless stem. The spores
have a double lobe appearance to them.
(400x)
T1-4
The spores on this part of the branch appear to be young spores, and seem to be mixed in with dark brown spots of fungus.
(400x)
T1-5
Hyphae, translucent ribbon-like objects, usually appear in association with the
spores. Here is an an attempt to capture a picture of a hyphae. These are said to infest the plant tissue in Phytophthora diseases.
(400x)
T1-6
This small branch protrusion hosts a number of spores. (400x)
T1-7
The spores here present a bit of a puzzle. It almost appears as if these white spores
have been newly created and are just emerging from the branch surface. Usually,
young spores are yellow in color. (400x)
→
→
↓
↓
T1-8
This vine wasn't in bad shape over the summer, so white canker evidence was
sparse. Nevertheless, here you can see it covering up the vessels (red arrows),
and a few hypha breaking through the bark (blue arrows). (400x)
T1-9
It appears as if the entire center of this small branch was consumed by canker,
which appears here with a brownish tinge, and is pushing into the sapwood.
obliterating the vessels there. (400x)
←
←
T1-10
These light tan blobs (red arrows) within the inner bark are the most difinitive
evidence of white canker. Note that the bark also bulges out at this location.
(400x)
↓
↓
↓
T1-11
This leaf cross-section shows diffuse canker in the upper-left, a cut spore
(with insides spilling out) (red arrow), and two hypha poking out (blue arrows).
(400x)
T1-12
In this leaf cross-section, numerous canker spores lie in the center of the leaf
on the left side, while a few spores lie on top of the leaf, along with some
diffuse canker material.(400x)
T1-13
This unusual leaf cross-section shows a thin band of canker buried in the
leaf's center. A hypha sprouts from this band, grows out, and gives rise to a
blob of white canker material.
(400x)
This vine grows on the south side of our house.
It has generally done well, but has been affected by white canker last year.
Analysis of a dead branch showed virtually no evidence of spores.
LA1-1
The picture on the left shows the leaf deformity, but the chlorosis is hard to see.
If you click the picture, the full view will show a fairly uniform sprinkling of spores on
the tops of the leaves and on the stem.
While there are few spores on the leaf bottoms, there is some spore clustering.
The leaf junctions are reddish in color but there are no spores there as on all the trees.
That was unexpected.
One interesting white canker clue is that there always seems to be spores
clustering on the underside of the leaf just about a half-inch after the leaf widens.
Coincidence? I flipped this sample over and scanned the other side.
The same pattern of clustering appeared, so I assume this lily IS susceptible to white canker.
LA1-2
But the biggest surprises came through microscopic exams of parts of the plant.
The picture above shows several spores with their typical shape and a small stalk
(lower right corner), just as we've seen on trees and shrubs.
It also shows two of the spores connected by a hypha, which is embedded
in the leaf, proving that these spores can infect a lily.
Note that the spore seems to change shape as it germinates to send out a hypha that in turn creates more spores. (400x)
LA1-3
This group of spores was located on the underside of a leaf. (400x)
LA1-4a
LA1-4b
My biggest surprise came when I ripped off a leaf and microscopically examined the leaf scar.
To my amazement I saw spores there!
I had previously assumed they only grew on the surface of stems and leaves,
and that only hyphae grew inside the tissue.
The pictures above show several spores within the scar area.
This scar area was exposed only a minute before this picture was taken,
so it is unlikely they spread to this area and instantly grew in that time period. (400x)
LA1-5
This view is somewhat unusual since it shows a side view of several spores which
are on the edge of a leaf. (400x)
LA1-7
Having now found evidence that these spores can grow within a leaf scar,
I wondered if they could also grow within the stem.
Fortunately, this being a plant, it was easy to make a clean cut of the stem with a razor blade.
Sure enough, I saw white spores within this cross cut. The picture above shows one of them connected to a hypha on the cut surface.
LA1-6
This picture shows a cut hypha pushed out of the cut stem.
Apparently the internal pressure forced it out, since the cut took place only a minute earlier. (400x)
LA1-8
This picture seems to show white spores buried just under the cut surface,
and a hypha star (mycelium) on the stem skin. (400x)
LA1-9
A buried hyphae star, or mycelium on the stem's cut surface.
These structures must be pretty tough to survive a razor cut fairly intact, and then pop out!
(400x)
LA1-10
This picture shows several buried spores, one of which is actually
penetrating the stem's skin. (400x)
LA1-12
Here we have spores on the edge of the cross-cut - the skin of the stem.
The rightmost spore apparently hasn't had time to do anything yet.
The one in the middle is losing its yellow color as it starts to send out hypha.
The spore on the left apparently has been cut, and its jelly-like insides have gushed out in blobs.
The two spores on the right seem to be transforming themselves into spore generators by changing their color and shape.
(400x)
LA1-13
This is a side view of a spore just below the surface.
To its right is a mass of a white jelly-like substance just below the skin.
This probably is the cause of the chlorosis seen on the plant - visible white canker. (400x)
LA1-11
↓
Here we have a normal white spore on the right.
On the left it appears as if a white spore is giving birth to a yellow/new spore (red arrow). (400x)
LA1-14
Above is a picture of a rare mottled brown hypha sticking up from the stem crosscut.
It extends about the same distance upward again, and then ends in an abrupt cut,
due to the razor. It must have been under extreme pressure to pop up so high. (400x)
LA1-15
↓
←
←
↑
Here again is a lower leaf surface with lots of white spores,
some apparently giving birth to yellow spores.
Several leaf stomata (breathing pores) are also shown (orange arrows).
One yellow spore is developing a cleft and turning into a mature spore (blue arrow).
The bottom yellow spore (pink arrow) is likely a child of the parent white spore next to it. (400x)
LA1-16
I've always wondered what''s inside those white spores.
This spore apparently has broken, spilling its insides (brown mess). (400x)
LA1-17
↑
↓
Here we apparently have two spores in the process of making new spores.
The parent spores are white. The new spores are the small yellow globules budding to their side. (400x)
Some of the most beautiful flowers in our yard are produced by a cluster of Asiatic lilies.
I noticed that they were suffering from chlorosis (yellowing), some of the leaves were a bit curled,
and the new leaves were pretty deformed.
This is a classic symptom of white canker. So I cut the top of a plant off for analysis.
As an experiment, I took one leaf that had a good sprinkling of white
mature spores on the upper surface, washed it under tap water for a few seconds,
and then gently rubbed it dry for a few seconds.
When I scanned it again, 99% of the spores were missing, indicating that they
weren't attached to the top leaf surface very firmly.
When I took another leaf and tried gently scraping its leaf surface with a razor blade,
I was unable to remove any spores.
I'm not sure why I couldn't remove any spores (maybe the blade only hit the high points on the leaf?).
When I started analyzing this lily, I thought I wouldn't learn much from it,
and almost didn't try. But to my surprise, it had a lot to teach me. Specifically,
- The white spores seem to be generators of the yellow spores,
which often grow to the side of them until they are full size.
When working with these diseased plants for awhile, I noticed that
my hands had numerous yellow spores on them, while there were no white spores on them.
- You can easily wash the white spores off the leaf surface.
- The interior of the leaves and stem are loaded with spores and hyphae.
- The loss of greening on the leaves only appears to be chlorosis,
but is actually caused by a buildup of a spore-related substance and hyphae.
Microscopic analysis shows the leaf cells themselves keep their color.
In summary, this lily is badly infected with white canker, in spite of the fact it has
only been growing a month.
The short time period means it has had little time for its parent spores to build new
spores which would spread white canker to other plants.
