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Dry Rot in Trees

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We lost a main branch from our tree in the backyard. I found what it seemed like dry rot. I scraped out excess but what can we do to repair e.g. put in a fill to prevent further rot?


Jenny from Geelong, VIC



Sorry to hear about your tree. The best advice I can give you is to get a licensed tree professional to come on site and survey the damage. Whether or not your tree can or should be saved depends on how important that main branch was to the overall functioning of the tree and how far the dry rot fungus has spread. Once a main branch is done in by dry rot, it's sometimes difficult to stop the spread of the fungus. It may be best to remove additional limbs or more of this limb in order to stop the fungus from growing.

Dry rot only spreads when moisture is present. Once the wood dries, the fungus stops growing. The problem is that the new wood inhabited by the dormant fungus has been altered in a way that makes it better at absorbing water. The next time it rains, this wood absorbs an even larger amount of water and the fungus starts to grow yet again. This is an ingenious survival strategy on the fungi's part, but it makes treating dry rot difficult. The truth of the matter is that the crumbly stuff you scraped out is usually what the fungus leaves behind. In other words, the fungus is out in front of the damage you can actually see. Sometimes the white cottony mycelium of the fungus is visible near the area, but other times it is not. I recommend consulting with a licensed arborist if you really want to save the tree or prevent further damage.


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September 29, 20060 found this helpful

When I discovered problem areas on a huge tree out back, I got busy and got a friend/climber to cut out ALL dead branches, unwanted branches, unhealthy growth, as much as possible. Within a short time I discovered the tree was healing ITSELF

afterwards, almost as if to say, "thank you, I had too little strength and you really helped!" Perhaps you can go ahead and trim all that you can, then

after digging out the dead rottenness, if not too

deep, just spray well with pruning paint. If in the

crotch of a couple of branches, it might be caused

by water accumulation. This was one of our cases, so I mixed up a large amount of MORTAR mix, like is

used on bricks, and filled the cavity to the max, tilting the finish so water would run off, not puddle

and cause more damage in the future. If that's not

possible, after cleaning out all you can, inspect with a flashlight to see if there are holes from borers. If

there are, I'd buy a large hypodermic syringe/needle

from pharmacist, and fill with tiny amount of pesticide to squirt into the borer holes, even though

my yard is organic. If no sign of borer holes, see if

it is showing new bark or tree beneath your cleaning

it. If raw tree is showing, I'd spray or paint with pruning paint. I'm not an Arborist, but I've saved many trees this way. If the ground is soggy, dry or

on unstable earth, it could be that there is a disease

that will progress. However, LOTS of trees have overcome disease IF it's not too late, and IF it is

not too extensive, and IF the tree is relieved of any dead branches. Treat the tree as if growing inside

your home, learning to watch it's leaves, branches,

ground cracking/mildew, etc. If evergreen, I'd use

coffee grounds like sugering a bowl of cereal, all around the tree directly under the outer limbs' dripline. If NOT evergreen, a leaf-losing tree, I'd

clean/repair/spray or patch/watch closely, until leaves

tell it's story. If they drop or droop, it's likely too late to have helped the tree. If they perk up, you did it a service and likely saved it. Borers are very tiny and can kill a tree quickly. If no one has cut into the bark of the tree, it might just have gotten accidentally damaged from a guide-rope when planting? Did you remove all guide-ropes when it

seemed to take root after planting. Sometimes folks

forget and the rope girds the tree cutting into it's bark layers and food/water absorbsion. Try not to over fertilize a tree, or to allow pets to use the ground below as a dump, or to allow kids to climb in it too often, or to overwater it. God bless you for watching over His trees. : )

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September 29, 20060 found this helpful

Thank you so much for the info - really helpful

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August 19, 20110 found this helpful

We topped a couple 3 inch branches many years ago on our now 30 year old Santa Rosa plum. I saw some white on the bark and stuck a screwdriver into soft wood. I cut some more off this branch and it had dry rot (white). I kept cutting and am now to the trunk and the dry rot continues. I dug out what I could.

Can I:
1) Use an antifungal paint (like I have used on the edges of my new roof (powerful, green, and oily) or antifreeze (glycol) which is water soluble or some borate to kill the dry rot? I wouldn't put any of this on the cambium. Any other suggestions to kill the last remaining dry rot?
2) Then fill the hole with blown in foam, smooth it off and paint to seal out pests, more dry rot spores and water. My main cut is now vertical.


3) No we don't want to remove and replace this tree.

By James D.

Answer Was this helpful? Yes
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