I saw another red maple that looked in sad shape, and decided to take a much closer look at it. Here it is:

Although there is only a dead branch or two, as you can see, the foliage is very sparse, and many leaves have already fallen. Curiously, the right side of this tree is mainly south-facing, so gets most of the sun. Apparently the sun's energy is helping keep this tree going.

Except for the leaves drooping and being rather small, I saw no canker on the top or bottom surface of them.

But the bark was another matter. Actually, as is typical, most of the bark is clean. However, there were extensive patches of spores at the underside of branch junctions, as shown in the following branch surface microscope photo taken at 400x:

Once again, the white spores are about 50 microns in diameter and the smaller yellow spheres are about half that size.

If white canker is really present, some of the best evidence is a detailed view of the cross-section of a twig or small branch. This time I took a quarter-inch diameter branch as a sample. Using my digital microscope, I then carefully took about 60 overlapping photos at 400x around the edge of the cross-section so I could capture all of the area just under the bark. I then used Microsoft's ICE photo stitching program to compose one large image. A small view of it follows:



This photo shows of how badly this tree is diseased. Only a trace of the normally green phloem is present, having been replaced by white canker material. The bark is separating from the phloem, as if it is trying to get away from it. Only a very thin layer of phloem remains immediately under the bark, and even there it only extends about half-way around. I've also made the full-resolution photo available on this website - check it out by zooming into it, at: www.whitecanker.net/pictures/2010-07-24 Maple branch cross-section donut.jpg
(Right click the picture to save it to your PC or to print it.) As you zoom-in to examine the details, you'll gain a better appreciation of how devastating this disease is to the inner part of the tree. The chaos there reminds one of a war going on. And, in fact, there is.

You'll note that these photos don't include the central xylem, which is usually a boring white. You can see the edge of it in the above photos. However, white canker does infect this xylem. Apparently it has killed part of the xylem in the center of this branch, as the following stitched photomicrograph shows:
The reason I suspect white canker killed this tissue is that there appears to be white canker within and around this black tissue. Not only that, but to the lower-left of this dead area is a patch of white canker blobs. Apparently, when the white canker density gets high enough, it kills off the white xylem tissue. Furthermore, as the snow-white xylem begins to die, it seems to turn brown, further highlighting the infiltration of white canker blobs.
 

Thanks for that. I will DIY this as i do everything else out here in the boonies.



Thanks for the correction. I thought the indentation you'd mentioned in the centers meant the whole sphere was flattened. I suppose i'll have to break down and buy a microscope...eventually.


Agri-Fos was first lauded as a cure, but downgraded to a renewable treatment. Still, if it works based on bark drenches twice a year...i like that. I remember thiophanate-methyl from the table of effective fungicide treatments you tried; did you find it ineffective after a while, or what?


Ah, that's what it appeared. I've not done that yet. Too bad climbing these learning curves doesn't burn any calories! 

Pentra-Bark doesn't cost that much, actually. I found a few sources on the Internet, but ended up buying mine from treecaresupplies.com for $24 USD per pint. It was worth it to me to get the satisfaction of treating my trees and shrubs myself.

Actually, I'd describe the white canker sporangia as roughly spherical, milk-white, about 50 micrometers in diameter, and almost always having two distinct lobes, sometimes with a touch of yellow between the lobes. They rest on a stalk that is only about 5 micrometers high and a few micrometers thick, so this stalk is very difficult to see as it is almost always hidden by the sporangia above them.

I wish I could treat once and be done with it I began  my treatment study by having a commercial lawn & tree care company do my trees. Of the four fungicides they tried, only Propiconazole and Mancozab were effective. And after about three weeks I noticed the white canker symptoms returning. Plus, these fungicide treatment company directions say to treat every 3 weeks or so. They're right! According to the directions, the fungicide doesn't kill the fungus, it just prevents it from making new cell walls. Its up to the trees to keep up the battle. A healthy tree can often live for many years with a white canker infection. After all, a well-seasoned fungus doesn't want to kill off the host that feeds it!

Yes, you can post pictures in this forum, as you can do in most forums. In fact, I just posted a note on our red maple trees dying, and that posting contains two pictures. Limit your picture size to 1024x768 pixels. The catch is that you have to place your pictures on some website, and then reference the pictures with a full URL (use the Preview button to verify you have it right). So you'll have to find some picture hosting website. Same with PDF files (although there is no size limit).

Here in New England, one of the most beautiful times of the year is in the fall, when the leaves turn color. And many would say that the most colorful trees in the fall are the red maples, which often turn a bright red. But these maples have been declining the past few years. There was one in our housing development which my wife and I agree is the best of the best - it turns a bright crimson red in the fall. We check it out every year. It has always seemed to resist attack by white canker. But last year I noticed the leaves sagging a bit more than usual. I was hoping it was just my imagination. Unfortunately, this summer there are a lot of its leaves dropping. Numerous branches within the canopy are dead. But, true, we are having a very warm and dry summer.

But other red maples are also showing signs of severe stress. In fact, one of my neighbors has one, and within a week every single leaf on it died! I had been following this tree. Several years ago a windstorm broke the top off, and soonafter it seemed to acquire some symptoms of white canker. (I assume the white canker spores got in through the large wound.) But I never expected such a sudden dieoff. Here's a picture of the tree:

Of course, by simply looking at this tree you don't get much insight as to why it died. So I broke off a small 1/8" (3mm) diameter twig, cut it with a razor, and then looked down into its cross-section with a 400x digital microscope. I took 20 pictures all around the periphery of the twig, and then used Microsoft's ICE picture stitching software to combine them all into one picture, which I include here:

(The inner white xylem is not shown since its not diagnostic.) As you can see, there is only a trace of the green phloem left under the bark (lower-left). Almost all the phloem has been infiltrated by a white fungus, so the normally green phloem is now more white than green. You can see the fungus almost oozing out from under the bark on the left side (hair-like translucent strands). The right half of this twig has started to die, and is turning black.

I suspect the reason this tree died suddenly was that it was just barely hanging on because its nutrient carrying system in the phloem was almost totally clogged with fungus. The recent heatwave combined with a relative lack of water simply pushed it over the edge.

Will it come back? Often times when a tree is hit with a massive defoliation, as with insects, it will refoliate within weeks, although this takes a severe toll on the tree's energy supply. In fact, the branch I sampled does have very small green leaf buds. But the severe damage to the green phloem argues for no comeback, or a very weak comeback. Meanwhile, will the homeowners give up on the tree and cut it down? Stay tuned...  (this is the third week in July - the hottest time of the year)

I wouldn't put much stock in the labeling. I used to have a favorite potting soil and told my friends, but this year the contents of the same packaging looks like chopped bark. It could be that "forest products" covers a multitude of sins, just as "animal by-products" in pet food covers some egregious ingredients.
In the alternative, it might be that you're getting a different type of bark.

I don't know your species there, but in MT we have "piss fir" aka white fir or grand fir, two Abies that smell like cat urine when cut. I've also smelled oaks that were just naturally awful-smelling. The devil's advocate position is that the manufacturer got a deal on some nasty bark from these species. Unless the bark is sterilized, i'd bet their are dozens of species of itty-bitties inhabiting the bark. Did you look at it under your microscope?


 

Don,

I just received a pint of propiconazole and will spray my trees as soon as the wind/rain/lightning stops, i'm not evac-ing for range fires (!), etc. I've been looking all over for a source for Pentra-Bark or Breakthru, by themselves, as i have the propiconazole in hand. In further reading about Sudden Oak Death, i note that Agri-Fos (correct spelling) plus Pentra-Bark is sold on eBay together, for about $250....quite a chunk of money to try it out to see if it works, considering that you found one of the fungicide trials ineffective. ("Agrifos", with no hyphen, appears to be an unrelated fertilizer company.)

To this end, i contacted Bill Stringfellow, a name you've possibly encountered if you've been reading about Phytophthora diseases, because his contact number was listed on a site that lists Pentra-Bark as a product. Pentra-Bark is made by Agrichem, an Australian company, with which Mr. Stringfellow is closely aligned. He seems especially engaged in discussions about Phytophthora ramorum, aka Sudden Oak Death. They use Agri-Fos and Pentra-Bark to treat that with some success. We discussed the possibility this is an outbreak of SOD in my area.

I expressed my doubts that this is P. ramorum on three counts: the spore images i've seen online for P. ramorum were lemon-shaped, and i read them described as such, whereas these "white canker" sporangia are more like flattened spheres, wouldn't you say? Secondly, the infected bark on trees with P. ramorum looks weepy and has a higher width:length ratio than the dry, split, expanded bark on our trees. Thirdly, root rot is a feature of P. ramorum infection, at least in some trees, whereas my infected trees readily sprout from the root collars. Trees i've removed due to continual die-back seemed to have quite adequate root systems. I've actually uprooted dead-looking trees, seen a healthy-appearing root system, and stuck them in the ground at the edge of the property, where they've sprouted from the root collar. They don't look good but they are still throwing up shoots years later. Your Rose of Sharon rising from the dead comes to mind. 

At any rate, Mr. Stringfellow is sending me some samples of Agri-Fos and Pentra Bark to try on these trees, in exchange for telling him about you, this site, and sending him the photos and PDF i prepared for our ag extension agent, to whom i took samples of tree bark, limb die-back, and wilting leaves two days ago.

I asked if mixing the propiconazole with Agri-Fos would decrease the chance of fungicide resistance developing, and he agreed it would. I've found a few sources online for fungicide resistance management, and here's the clearest table i've found so far from Purdue Extension (for pome fruits, but i'm assuming the basis for mixing different classes of fungicides still holds):  www.ces.purdue.edu/extmedia/bp/bp-72-w.pdf  If i find a better table later on, i'll share it.

We talked about application rates and timing. He suggested spring and fall bark drenches, rather than monthly. Are you treating monthly just because you got in the habit from foliar spraying monthly, or do you notice an uptick in symptoms one month post-drenching? Or maybe you haven't had enough time to decide yet? If semi-annual treatments would suffice, it would certainly be a more supportable spraying schedule, as well as decrease our use of chemicals, and lessen the strain on our mad-money budget! 

It sounded like Mr. Stringfellow intends to contact you, and says this is timely as there is an industrial-strength tree-huggers meeting in Chicago soon, which he will attend. He also said that considerable money is being thrown at the research on P. ramorum. I guess that's either an indication of the severity of the disease or alacrity of the fundraisers, lol. We can hope that this can either be folded into that knowledge base, or create another area of interest.

I so hope this disease gets the attention it ought to be receiving. More and more people are starting to note how many trees are dying, and it's not just due to harsh winters. I have Chinese Elm kicking the bucket now...a tree you could only kill previously by driving a stake through its heartwood. Another neighbor came over to discuss this a couple hours ago, after noting my hoophouse and thinking i might know things. ha ha ha...

Don, is there any way to attach files here? As you can see, i'm a hot-linking fool, and i'd also like to attach my PDF and pictures within my post to add to your public service on this issue.     

Thank you for the feedback Colleen. This website gets a fair number of visitors, but for some reason people don't post in this forum (except for spammers - I'm wildly popular with them for some reason!).

You're right-on when you say a very wet spring brought on more symptoms. White canker is a fungal disease that thrives on moisture either on the bark of a shrub or tree or just under the bark (in the green phloem nutrient transport system). Its growth is more vigorous in these locations. Propagation via spores takes place on the bark surface.
 
Your symptom observations on a variety of trees agrees exactly with what I'm seeing. For example, white birch trees, which were fairly common around here in years past, now are becoming a rather rare sight - especially healthy birch trees. Most seem to be dead or dying. Yet no one seems to be noticing it. I'm guessing that nobody is noticing this because the die-off is taking place over a several year period. This disease is usually not a quick killer.
 
What I REALLY wish some people would do would be to look at the leaves and twigs and bark of these diseased trees/shrubs under a 400 power microscope so they could actually see that the inner bark is being eaten away by a fungus, as if it is being dissolved by an acid.
 
My fungicide effectiveness studies still stand. However, my tree-care company recently increased prices dramatically. So I'm now experimenting with treating my trees and shrubs myself. There is no way I can reach the top to tall trees, or most trees, so I'm trying another approach: I mix the systemic fungicide I found effective (Propiconazole) with a chemical that helps it penetrate the bark, and then spray this mixture all over the trunk, from ground level to about 5' high. It's called a "trunk drench". I just started testing it this summer, and so far it's very effective. Trees that were previously dying are now nice and healthy. But since this treatment doesn't kill the fungus (according to the fungicide manufacturer, it just keeps the fungus from building cell walls), you have to repeat treatments every 3 or 4 weeks. I'm probably going to post more details in another note, e.g., exactly which trees & shrubs I treated and exactly what effect it had.
 
Yes, using a variety of fungicides would be ideal. Unfortunately, I don't have the means of evaluating a wide variety of fungicides - I can only evaluate what commercial tree care companies use. Plus, some fungicides may have harmful effects on pets, plants... or us! I was hoping that others would test other fungicides and post the results on this website. But nothing so far. I guess people in general still don't really believe there is such a thing as this white canker fungus. Even our state university plant pathologist doesn't believe it!

Oh, I should say that during a wonderful tour of Mt. Auburn Cemetery, in Cambridge MA (which has a huge variety of trees), it was pointed out that some beech trees were in a state of decline (sure looked like white canker to me), and that Cornell was trying an experimental treatment. I got the name of the researcher there, called him, and found that they were doing "trunk drenches" using a chemical call Agri-phos, along with a bark penetrant. I was surprised to find out how similar our treatments were! As far as I know, since they are still in a testing mode, nothing about its effectiveness has been published.
 
I don't know if the name "white canker" will stick or not when it becomes more widely known. But it needs some name until we come up with a better name, or until some lab identifies exactly what kind of fungus it is. Right now, most experts are dubious about this disease when I say that it attacks almost all trees and shrubs to some extent. Strangely, none of the experts I've contacted seem to have an interest in looking into it. When pressed, they say they "don't have the time" to review the evidence!

For those who really care about the health about their trees and shrubs, I hope this website helps.
 

If you live here in the the Northeast United States, you may have noticed that pine trees have been dropping their needles this summer, when they should be doing that in the fall. This issue was discussed recently in a UNH Cooperative Extension Education Center Newsletter article, where the needle drop was referred to as "epic".
 
Curious as to exactly what is causing this disease, I took it upon myself to gather more factual information regarding this apparent tree disease. Specifically, I examined a red pine and three white pines, recording damage to the outside bark, inside bark, needle surface, and needle interior. What I found does not appear to match the symptoms of known pine diseases, specifically needlecast. Vermont officials seem to agree that we may be seeing something new, saying that this disease is still "under investigation".
 
All the disease data I've gathered on this pine disease is detailed in a set of over 40 photos contained within this website PDF file: www.whitecanker.net/Pine needle drop analysis.pdf. Most of the photos were taken with a digital microscope so you can see exactly what sort of damage this disease is doing within the tree, as external views don't tell you much.
 
Remember, PDF viewers have the ability to zoom in to content, so you may want to use this feature to more closely examine some of the photos.
 
If you have additional information regarding this pine tree disease, I'd love to hear from you! In fact, we can all discuss it. Just reply to this note.

Don Peters
Nashua, NH

I've been using bark mulch in my yard plantings for over 35 years. I've used it for a variety of practical reasons: looks, moisture retention, weed control, and erosion control. But another reason is that I simply enjoy handling it and putting it down. In fact, I often use both hands to grab a bunch of it, and then smell it before I place it. I find the smell of bark mulch to be very aromatic, and think of it as nature's perfume. I've talked to other guys who feel the same way.

No more. I recently had a truck load of bark mulch delivered. I checked its smell periodically, and instead of finding it pleasant, I found it repelling. So much so, that I actually tried to avoid getting my face near it.

When I ran out of this mulch, I picked up a few bags of hemlock mulch at our local Home Depot. The brand was Timberline, and was the dark variety. I thought hemlock would smell better. But it was worse. The smell in all cases was of strong moldy odor. None of the past bark aroma was there at all.

My mulch needs were greater than I thought, so I want back for more. Home Depot was out of the blue Timberline hemlock mulch bags, so I bought their bags of hemlock mulch that had red coloring on the outside. The mulch inside was of a red color. The mold smell was still there, but not as strong, and there was only a faint appealing bark aroma. I tried calling the Timberline manufacturer, but no one answered their 800 number. So I called their local number. No one answered, so I tried to leave a message, but their answering machine cut me off saying it heard no audio! So I tried to contact them via the Internet. Fortunately, I received a nice reply from their agent Kathy Perron, who said the hemlock came from "hemlock bark and composted forest products" in Maine (the next state over). The red mulch isn't really bark mulch (the bag calls it "Hemlock Mulch"), and is made from "softwood logs, ground and dyed with a carbon based dye". In summary, it cost more, had a slightly better texture, and less of a mold odor.

Unfortunately, my wife absolutely hated the redish color of the mulch (I liked it, thinking it was more of a red-tinted brown then red), so I went back again to Home Depot and this time bought Scott's mulch, made from forest products. This mulch also had a somewhat moldy smell with almost no pleasant aroma. It was also dyed - a nice "deep-forest" brown.


Consequently, after all this experience, now when my nose gets near this (bark) mulch, I hold my breath so as to avoid smelling it. What a shame.

So, why the change in bark aroma? I'm guessing it's due to white canker. Here's why. While white canker does infect leaves, microscopic examinations show it is primarily a bark disease. More specifically, white canker fungus feeds on the nutrient-rich inner bark, destroying it. While destroying it, the fungus prevents nutrients from migrating outward toward the outer bark. You can see this on the bark surface of infected trees - new bark often doesn't get created, and existing bark is cut off from the chemicals (often aromatic) that prevent other fungus from attacking and consuming it. In fact, bark on infected trees will simply look unhealthy, as if it is decaying. It is.

When such an infected tree is cut for lumber, the unhealthy, decaying bark is stripped off and ground up to produce bark mulch. This bark mulch therefore strongly smells of mold/fungus precisely because it contains a large amount of it.

A closely related issue is whether this infected bark mulch will damage the plantings it resides among. I don't think it's harmful, and so far I haven't seen any harmful effects. After all, all bark mulch will eventually decay naturally anyway. This natural decay is now simply given a head start, so the bark mulch probably won't last as long as expected. In fact, I'm seeing this now - the bark mulch I put down several weeks ago seems to be disappearing!

As do many others, I love the look of bark mulch. But based upon my experience with it combined with my research into white canker, I'd recommend avoiding "bark" mulch, and instead go with mulch composed of ground up wood, since the interior of a tree is usually not much affected by white canker.

Damn, I miss that sweet bark aroma!

Hello Don,

I've read your website pretty thoroughly now, because i think you've nailed what is wrong with all my trees, too. This year brought a very wet, cold, extended spring and so the damage to the trees is pronounced. Because the damage is so extensive, and among so many species, i turned to Google images and found the splitting bark that characterizes this disease, which i've described as "cat claw marks". For a long time, i thought to protect the tree boles from my cats with wire cages, which did no good, of course. The google images found on your site describe the damage here and on other trees in the vicinity - and in the "sale" aisles at the nurseries! - just about perfectly. I thought perhaps i'd brought it into my area by buying sale trees, but i've noted similar symptoms on inspection of my neighbors' trees, as well as others up to 40 miles away; it's a widespread problem, for sure.

Your synopsis of most affected tree species fits well, too. In my case, the first casualties were some mountain ash. I put it down to bad soil. I replanted, amending as i went. Then the birches died, including one that was about 12' tall, whose girdling black band about 2' above the ground was so weak as to make the tree start to bend to the ground, such that i propped it up until it died. All my maples are exhibiting the very typical split bark and cankering, broomy branching with many limbs growing downward, and wilting leaves. My lone ginkgo is exactly as you described...no bark lesions, but just a few leaves this year, with the downy white hairs on them. Prunus of all kinds are severely affected; apples and pears are a mixed bag. Also i note that leaders often die, and that there is a pronounced sucker growth at the base. Curiously, ants are swarming on the trees in proportion to their observed lack of vigor: sicker trees --> more ants. Locusts are less affected, and bur oak show no observable effect, which in interesting in that SOD disease would seem to prefer them.

Now i'm looking at your fungicide choices and wondering if you've updated that at all, since it appears the website was created in 2008 and the forum has seen little traffic so far.

My concern is what i've been reading about risk of resistance to fungicides. I've been emailing with an orchardist who recommends using more than one fungicide at each spraying, from different groups, to ward off creating pathogen mutations resistant to a particular fungicide, thereby eliminating its usefulness. I'm wondering if you've had any experiences with that, or with other fungicides you've tried besides the ones listed, or any other information you can share; e.g. i've been wondering what the effect of using something like copper might be on the disease, but would rather not reinvent the wheel if you've tried it. Any further information you have in this area would be most welcome.

I can't thank you enough for putting such a Herculean effort into the website. I've looked at other Phytophthora species and their effects, and without being a botanist it seems clear to me that the set symptoms you describe are indeed not matched by other set of symptoms i've investigated on the Net, but they match my experience of the disease nearly perfectly. I wouldn't have known what the next step was without your "white canker" work. Maybe they'll name it after you when they "find" it, eh?

Thanking you in advance for your consideration,

Colleen Miller
Stevensville, Montana