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Steve Nix

Leyland Cypress and Seiridium Canker - Seiridium Unicorne Damages Leyland Cypress

By September 19, 2007

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My Leyland cypress hedge has Seiridium unicorne canker fungus. The canker, also called coryneum canker, is a big problem on Leyland cypress trees. The fungus will destroy the cypress' form and cause eventual death if not controlled. Seiridium canker is usually localized on individual limbs. The limb is usually dry, dead, often discolored, with a sunken or cracked area surrounded by living tissue. In many cases there is a gray discoloration at the point of infection.

Fungal spores are washed down the tree or splashed from tree to tree by rain or overhead irrigation. New infections develop when spores lodge in bark cracks and wounds. You should always destroy diseased plant parts and try to avoid physical damage to plants. Sanitize pruning tools between each cut by dipping in rubbing alcohol or in a solution of 1 part chlorine bleach to 9 parts water. Chemical control of the fungus has proven to be difficult but some success has been noted with a full-coverage fungicide spray at monthly intervals from April to October.

Leyland Cypress With Seridium Canker - Photo by Steve Nix and Licensed to About.com


December 9, 2006 at 2:43 pm
(1) David Leon says:

Any luck controlling the Seiridium canker? If so, what fungicides were used?
Thanks, DL

September 10, 2008 at 2:28 am
(2) winnie says:

I have 4 Leyland cypress planted about 8 feet apart. I planted them about 5 years ago. They are doing well. One is stunted from deer rutting and damaging the trunk, but it is comming out of it. This summer I found some small white slimy bags hanging from the branches I quickly sprayed them with malithion until they fell off. Have not seen any damage and it has been about 2 months. Any idea what that was??

September 12, 2008 at 11:33 am
(3) forestry says:

You probably have bagworms. Check this site out…

Steve Nix

November 14, 2008 at 8:46 pm
(4) Winston says:

Can leyland Cypress be milled ,im thinking of it dressed and used as panelling in a kitchen makeover, Cupboards,drawers etc
Regards Winston Gray

February 14, 2009 at 9:06 am
(5) david mcintosh says:

my leylands do show the seirdium cancer, what can i spray on?

February 16, 2009 at 8:52 am
(6) Phorester says:

Chemical control of this disease is not reliable. Even if it was, all foliage of every tree has to be sprayed once a month from April to October. Easier to just cut out the few branche tips that have died back. Will probably need to be done only once or twice a summer.

May 3, 2009 at 8:28 am
(7) Mike says:

how do the roots of a leyland cypress grow and i am planning to plant my trees in my front yard were my septic tank a good 15′to 30′ feet away.

June 10, 2009 at 5:58 pm
(8) Jason says:

We have about 10 leyland cypress trees that are about 2 1/2 years old. They’ve been doing great until recently when one started turning brown. We removed that tree but now have brown spots on about 4 trees. What causes this and how can it be stopped? The trees are planted in an area that gets alot of water when it rains and the temperature gets up to around 100 degrees during the summer months.

June 11, 2009 at 9:51 pm
(9) Vivian Crawford says:

I’m not sure if my trees have this seirdium cancer. I have 8 leyland trees and they were planned two years ago. They all have brown branches at the bottom of the trees to half way. I haven’t seen any bugs of any kind on them. Not all the branches are brown but I’m concern, what can I do? Do you think it’s the seirdium cancer?

July 7, 2009 at 2:16 pm
(10) Wendy says:

This must be our problem-I need to treat the whole tree- we’ve already lost 4 to this canker. Can you suggest any treatment?

April 5, 2010 at 9:18 pm
(11) les says:

I have 85 lelands bordering my entire back yard which affords me complete privacy. However, i have lost 4 to canker disease and others have isolated branches that are dead. These trees are matured at 30-35 feet. A great looking tree but not tolerant at all.

May 8, 2011 at 6:34 pm
(12) Sharon says:

Sounds like we all have the same problem and there is no cure. Wish I had heard about these diseases from my nursery when I purchased them. Sounds like the more we plant these the worse it spreads.

May 11, 2011 at 8:29 pm
(13) David says:

The only way to combat these diseases is with proper cultural methods when planted and making sure the trees are as healthy as possible. That means mulching, watering, pruning, fertilizing all as necessary and based upon soil testing.

March 29, 2013 at 5:02 am
(14) Dan Lediaev says:

When this problem is first noticed from a distance you will notice that the colour of the foliage is turning, we use a product called ‘rogor’. If not tended to you could lose the tree within weeks (2-3) All the best.

September 25, 2013 at 2:36 am
(15) richard says:

I have eight Lyland Cypress trees and I did experience all the problems all-of-you experience. BUT I have not Loss any of my Lyland Cypress trees. The secrete for me is insecticide
I am currently using Cross Check X plus multi-insecticide.
You can also use Talstar Professional insecticide.

Whenever I use the insecticide above on my Lyland, the desies always goes away; Brown branches/leave become green again.

My trees are between 10ft and 6ft., and they look nice.

Remember once you mixed your insecticide you do not just spray the areas that have the disease/damage/brown leaves, you spray the entire tree. Make sure you spray the Lyland that the insecticede is running/dripping off the tree.
Do this every seven days, for a total of 21days.
This mean: spray1- seven days past,
: spray 2-seven days past
: spray3-seven days past
You will see improvement after a month from you last application.
You can always apply the above insecticide on the Lyland once you notice any problem. Or just use the insecticide as a preventative measure.
This really work for me and i hope it work for all of you.

There is one more thing i want to mention:
When I first plant my Lyland Cypress. I end up over watering one of them, plus I have clay soil and for a month I got a lot of rain. To make the matter worst, if I did not get rain a day Or two, I would water it. I did not know i was over watering it. The branches was turning Brown and falling off the tree. When I realized I cannot save the tree. I have it removed, but the hole had so much water in it, you would think a Pipe was burst in that hole.

So my friends be careful not to over water, especially if you live clay soil.

Good luck!

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