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Uh oh, any ID on wilt disease on Cornus Controversa

Posted by toronado3800 Z6 St. Louis (My Page) on
Sun, Aug 4, 13 at 11:58

It's been a rough year for trees on my street! First last year's drought and heat, then this year's tornado. Throw in what an extension agent said was verticillium wilt that killed a decade old acer palmatum and appears to be getting one of my neighbor's lilac's.

Now I know it is late summer and foliage problems are not the biggest concern. But I found bark discoloration and retained shriveled leaves up "high" in my 8 foot tall cornus controversa. Any ideas? I'm planning on calling the extension fella tomorrow but what else should I be looking for.

 photo 20130804_101636_zps7c9ea368.jpg

 photo 20130804_101619_zps46baa62f.jpg

Oh, yes, I sterilized my cutting tool afterwards. Um, tree was a small mail order transplant several years back. Looks otherwise great except for maybe a 1/2 dozen leaves maybe towards the interior of the tree showing some fall color. Gets maybe 7 hours of sun planted on a west facing slope uphill from my septic a few dozen feet. Clay base soil, decent drainage there. Above average moisture most of this year until one dry patch a few weeks ago and I actually did water the area once for several hours with the sprinkler.


Follow-Up Postings:

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RE: Uh oh, any ID on wilt disease on Cornus Controversa

toronado,
Split the joint (I just pulled it apart) between the affect branch and the normal branch you also pruned out. See if there is discoloration there? This is where I found a canker on our redbud a couple years ago. It produced one small branch with discolored leaves, and that was what I noticed. Regardless, looks like you pruned out well below the affected branch, which is exactly the right thing to do. Keep us posted.

Arktrees


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

Darn it! Another branch on the opposite side of the tree caught the black shrivels by the time I got home.

Here is a picture of the new bad branch. I am going to go cut the other one and post pics also.


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

Nothing exciting in there to my untrained eye. This plant always has the hollow stems.


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

The dark area which ends just below the "Y" suggests Pseudomonas, common on woody plants which previously had minor winter damage.

In order to check for verticillium stain, the branches should be the diameter of a thumb.


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

Thanks for the info. I was thinking verticillium because one of my Japanese Maples was probably succumbed to it. So far no inch thick dead branches on this one.

A week or so back I mulched a bit around the tree. Any chance this is the culprit? Cheap box store cypress mulch.


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

OK, I have emailed the extension agent.

Oh yeah, and I noticed some leaves with spots on them this evening:

 photo 20130805_020514_zpsdfa0995f.jpg

Here is my most recent pic of the whole tree from July

 photo 20130707_201437_zps71870602.jpg


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

IMHO, has nothing to do with Verticellium from what I see. Just doesn't look like the pattern. The leaf spots are likely due to wet weather IMHO, giving something an advantage over the tree. Leaves are rarely perfect this time of year, so unless it gets allot worse, I would not worry about the spots at this point.

While I don't know if jean has the right pathogen (would require more extensive testing(, I do think they have the right ideal. Namely that it is something that got into a small wound etc. Your pictures seem to chow that it is working top downward. As for what to do about it, as indicated before, it looks like your doing exactly what needs to be done. That is pruning out to well below the affected area, with proper disposal of pruned material (i.e. burned or in the trash, but not in compost).

As for the mulch, it probable has nothing to do with it. However I will say this about cypress mulch. From what I have been told, in many cases this mulch is obtained by removing entire tree from the swamp ecosystem for no other purpose than to make mulch. At this point the ecosystem is often so disturbed that seedling cypress do not survive. It is for this reason I don't use cypress mulch any longer.

Arktrees


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

Hope it's not "golden canker" getting started on your tree (see link). C controversa is related to pagoda dogwood, so it may be susceptible.

Here is a link that might be useful: Golden Canker


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

The extension agent said it was not vert wilt as he saw no staining and the species is resistant. He set me upon looking for evidence of insect damage.

Well it has been a week and all has looked well. Tonight I found this broken twig partially attached to the tree. See the line of small holes underneath the dried up part? There were a couple more up the stem. In a way I am relieved.

If the bug was just eating leaves I might let it go but this seems able to kill branches so I will probably ask him for an insecticide recommendation.


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

I don't know the specific insect you may be dealing with, but it would probable be wise to try to ID the insect first. If it isn't going to cause big problems, then you might leave it alone, conversely, you might need to treat ASAP. We have had some problems with Maple Tip Borer. These kill the young growing tips of maples. One year they attacked our Fall Fiesta Sugar Maple (the Commemoration has been left alone by them), killing allot of the growing tips. The next year I treated with a systemic, and there were no problems. I have not treated since. While they have come back in the last few years, the amount of damage has been less and tolerable. They have also affected our Autumn Fantasy and Autumn Blaze maples, but not seriously damaging them.Point is that it may be that they never cause a real problem, or one careful treatment will be enough to restore balance, but you need to try to find the causal agent if possible.

Arktrees


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

I believe you are looking at black twig borer (Xylosandrus compactus) - an ambrosia beetle. It is an exotic and carries a Fusarium (fungus) that kills the twigs it bores into. It is definitely not Verticillium or a bacterial issue.


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

Thanks guys. I think the Xylosandrus compactus idea seems to fit if it has reached this far north. Is there a test for them?

I did some searching today and found another trig starting to turn darker colors. Sure enough below the change I found a hole. I disected it looking for muck inside like I saw on one of the Xylosandrus compactus web sites but it looked pretty clean.

I also checked all over the remnants of my neighbors lilac. It has only one hole on the four sickly branches it has and I do not see the discoloration so oerhaps that is unrelated.

Ark, you are right. I need to figure this out to see where I stand. If there is no cure there is no cure but hey, I can take pics and email or post easily enough.


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RE: Uh oh, any ID on wilt disease on Cornus Controversa

You often will not find the offending insect for whatever reason. In the case of the Maple Twig Borer I mentions, I actually found the grub maybe 50% of the time. Just the same, seem you have the most likely candidate. By all means keep looking, but you may have another use for the insecticide you just bought if the extension agent can't recommend something else.

Arktrees


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