How to Identify, Prevent, and Treat Gummosis on Fruit Trees

Leucostoma persoonii and Leucostoma cincta

Gummosis refers to the oozing of sap or gum from a tree. This behavior is very common on stone fruits, including apricots, peaches, and plums.

You can look at gummosis as your tree’s cry for help in the face of any one of a number of problems.

Close up of a cherry tree trunk that's oozing dark sap in a condition known as gummosis.

The most common cause of gummosis is a fungus originally called Cytospora that is now called Leucostoma.

This fungus is opportunistic. That means that it infects easy targets like weakened trees. It requires both a wound and a tree that is stressed.

Pruning cuts are a major source of entry for this fungus. Sunscald and cold injury – and even deer rubs – can make your tree vulnerable to Cytospora infection.

Prevention is the best way to manage this condition.

Two Leucostoma Species Infect Fruit Trees

Two species of Leucostoma can be on the attack. L. persoonii is more likely to infect apricots, plums, peaches, nectarines and cherries grown at a low elevation. This species is more of a problem in warmer climates.

In contrast, L. cincta is more likely to attack apples and cherries in cooler areas, like orchards at high elevations.

Both species of fungus are widespread in the US and throughout British Columbia and Ontario, Canada as well. They have also been known to cause problems in South America, Europe, and Japan.

How to Diagnose Gummosis Due to Leucostoma Canker

Your tree will exhibit symptoms like dieback of the canopy and tree flagging. And it will produce a lot of gum. Think excessive.

Close up of a the trunk of cherry tree with leucostoma canker and gummosis.
The trunk of a cherry tree infected with L. persoonii showing signs of Leucostoma canker and oozing sap.

The gum that Leucostoma fungi produce has a dark amber color. Scrape off the bark and look at the phloem underneath. It will be cinnamon brown.

Typically, the fungus grows during favorable times like the winter and spring. When the tree starts actively growing, it walls off the infection until it loses resistance again in the fall. You can see this pattern in the form of bands of lighter and darker colored tissue.

To distinguish Leucostoma canker from other causes of gummosis, you should look for its fruiting bodies – protrusions from the surface of the woody tissue that look like small black pimples.

These fruiting bodies can produce thousands of spores, and those of L. persoonii can travel up to 260 feet.

How to Prevent Gummosis

Cultural Controls

1. Optimal Fertilization and Care

Since the primary causal agent of apricot, peach, and plum gummosis attacks weakened trees, do your best to keep yours healthy with optimal mulching, watering, and nutrition.

You should consider fertilizing with nitrogen in the late winter or early spring. This will prevent your tree from producing growth that could be damaged by cold in the fall.

2. Prune Precisely and Remove Damaged Tissue

Be very careful when you prune. Make proper cuts and do not prune in wet weather. It is important to not leave stubs or flat cuts and to not make flush cuts.

Remove infected limbs and twigs by carefully pruning back to the healthy wood. You should do this during dry weather in the summer if possible, so the wound will heal as quickly as possible.

Sterilize your tools with Lysol wipes or 10% bleach between cuts.

It may not be possible to prune out all of the damage if the fungus has spread.

3. Protect from Sunscald

Protect the bark of your tree from sunscald during the winter. To do this, you have two choices.

One is to paint the trunk with half white latex paint and half water.

A human hand uses a paint brush to apply thinned latex paint to the trunk of a fruit tree.

Your other choice is to apply white tree wrap from December to March.

4. Protect Against Rodents and Insects

Treat for rodents and insects, so they won’t create wounds in your tree. Some growers spray insecticides to keep borers from generating holes in the trees.

5. Drain Water from the Base of the Tree

You want to be sure to prevent injury to the crown from the cold. You can do this by draining water away from the tree’s base.

Chemical Controls

If you live in area where this pathogen is widespread, you should treat your tree with chemicals as a preventative measure.

Apply captan, thiophanate-methyl, or lime sulfur (Bordeaux mixture) in 50% latex or kaolin clay to freshly cut pruning wounds. Do not apply copper hydroxide, since this has been shown to be toxic to the trees.

Lime sulfur mixed with white latex paint is used to protect a large pruned limb area from infection.
Use a lime-sulfur solution (Bordeaux mixture) mixed with white latex or kaolin clay to project freshly pruned areas from infection.

If your trees are part of an organic program, lime sulfur is safe to use.

Monitor Your Tree Closely

Try and make sure that your tree is not stressed and doesn’t have any wounds on it.

Leucostoma canker is common in backyard trees, so be very careful when you prune them. You may want to apply a chemical treatment after pruning, so the fungus will not be able to enter through pruning wounds.

Close up of gummosis on an apricot tree trunk.

Keep an eye out for gummosis. If you see it, try and determine if it is due to fungal injury. If so, quickly prune out the damaged tissue before it spreads.

And if you do lose a tree to this fungus, please remove it. The fungus will continue to live on the dead tissue and will keep producing spores to infect other trees.

Have you waged war against gummosis in your garden or home orchard? If so, let us know how it went in the comments.

© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Uncredited photos: Shutterstock.

About Helga George, PhD

One of Helga George’s greatest childhood joys was reading about rare and greenhouse plants that would not grow in Delaware. Now that she lives near Santa Barbara, California, she is delighted that many of these grow right outside! Fascinated by the childhood discovery that plants make chemicals to defend themselves, Helga embarked on further academic study and obtained two degrees, studying plant diseases as a plant pathology major. She holds a BS in agriculture from Cornell University, and an MS from the University of Massachusetts Amherst. Helga then returned to Cornell to obtain a PhD, studying one of the model systems of plant defense. She transitioned to full-time writing in 2009.

4.8 5 votes
Article Rating
Notify of
Newest Most Voted
Inline Feedbacks
View all comments
Doris Moravetz
Doris Moravetz (@guest_5180)
1 year ago

I was told my orange tree has this and to use Monterey garden phos., and he said “foot rot” also. Lost instructions- do I spray on root areas also?

Michelle (@guest_5725)
11 months ago

I think my tree has gummosis. What should I do?

Lauren Maier
Lauren Maier (@guest_5870)
10 months ago

I have a fruit tree that has a huge opening in the trunk that I believe has gummosis. Once it is in the trunk, should the tree be removed or can it be treated?

Jessica (@guest_5908)
10 months ago

Hi. I have a mango tree and not sure if it has gummosis. The leaves also have brown around them. Please look at the pictures and give me any suggestions… thanks

Rick Perkins
Rick Perkins (@guest_6323)
9 months ago

Hi, my peaches are all oozing a clear hard substance. The rest of the tree looks great. Any ideas?

Kathy (@guest_6892)
Reply to  Helga George, PhD
8 months ago

That looks like damage due to the oriental fruit moth to me

Paul Hartshorn
Paul Hartshorn (@guest_10553)
Reply to  Helga George, PhD
2 months ago

My peaches look similar – splitting with a clear substance oozing from them. A local nursery said definitely gumosis. And now that the leaves have fallen I see a some amber colored jelly like substance in a couple of places on branches.

Paul Hartshorn
Paul Hartshorn (@guest_10554)
Reply to  Paul Hartshorn
2 months ago

FWIW I should add that I live in a high desert environment and it can get windy here in northern Nevada…

Ashley (@guest_6613)
Reply to  Rick Perkins
8 months ago

I don’t doubt the stink bugs but it’s also caused by a white Chinese moth. My poor beautiful peach tree is now dying from gummosis! I’m afraid it will has to be cut down. Probably got it from when it was pruned last fall. Maybe from the pruning equipment or got in there in the wounds. Those moths are crazy killers, can’t get rid of them.

Stephanie Dickerson
Stephanie Dickerson (@guest_8657)
Reply to  Rick Perkins
6 months ago

My peaches have this coming out of them. What can I do to prevent this from happening next year?

Gabriel Diaz
Gabriel Diaz (@guest_6387)
9 months ago

After researching on the web, I believe my mango tree has gummosis. Any advice that you can give to help me bring this tree back to a healthy state would be much appreciated.

Gabriel Diaz
Gabriel Diaz (@guest_6394)
Reply to  Helga George, PhD
9 months ago


Please advise on “spray with copper,” not sure what you mean by that.

Also, I read that I should sterilize a sharp knife and cut 1 inch around cracks and peel off the bark to allow the healthy wood trunk to heal itself.

Is there a spray to hook up to a hose, like from Home Depot, that would help with the first picture, what looks like fungus on the leaves and fruit branch portions?

Thanks again…

Neha (@guest_7231)
8 months ago

Do you think my peach tree has gummosis? What can I do?

Abe C.
Abe C. (@guest_7369)
8 months ago

Around 30% of my peach tree leaves started curling with bulges, some yellow leaves, and of course sap leaking from the stems. I’m more than positive this is Gummosis from fungi but in your expert opinion do you think the curling is a byproduct from the Gummosis since it’s also fungi based or is it two different types of fungi causing both Gummosis AND peach tree curling? Is it also too late for any meaningful preventive measures? Just today I have started pruning but I have little hope it’ll prove effective.

Gaia (@guest_7542)
8 months ago

Is this gummosis? i just recently noticed this on my lemon tree and some branches have died already and I had to cut them off. I was planning to spray Dithane contact fungicide and was wondering if it could cure them, but afraid to spray directly on fruits as it might affect them too. thanks!

Milla (@guest_8119)
7 months ago

Last year I planted bare root North Star cherry. This spring it started leaking sap in five sap mounds on the trunk, starting about four feet above the ground .The sap oozing from cherry tree is free of sawdust.
Is it harmful for the tree? What to do? Thank you in advance, Milla

12 (1).jpg
12 (2).jpg
Amy Seek
Amy Seek (@guest_8304)
7 months ago

My prunus also appears to have gummosis, and what I haven’t found addressed anywhere is how to deal with it on a tree that is very very young — no more than 1/4 inch caliper, planted just last fall. I couldn’t possibly remove much without killing the tree entirely. Is the tree lost? Any treatment possible? Thank you!

Amy Seek
Amy Seek (@guest_8330)
Reply to  Helga George, PhD
7 months ago

I do not see evidence of borers. Would you advise not to apply copper until I’m sure of the issue? Appreciate your help, and I’ll plan to call the extension service today.

Amy Seek
Amy Seek (@guest_8346)
Reply to  Helga George, PhD
7 months ago

I will let you know! Thank you.

Lou (@guest_8423)
6 months ago

Hi Helga   I am wondering if my flowering peach has gummosis. Do you think there is any way I can save it? It appears to be on the majority of this front side and I don’t think it would be possible to prune it away due to the extent. I am wondering if I can try and build the tree health to help.. It looks very healthy during summer (it is currently winter where I am) however, I noticed during summer gone that this side had less growth. I have never pruned my tree, I am thinking the damage… Read more »

Paula Mohr
Paula Mohr (@guest_8520)
6 months ago

Can my cherry tree be saved or should I cut it down and re-plant? I planted it in fall 2009 and it has been a productive tree. A few years ago, it started leaking a little sap and now it has multiple sites. My fault for not doing something sooner. The open/oozing site in photo is on the south side of the trunk toward the bottom. Pictures attached. Used to be a small branch or two looked dead. Now more branches are leafless. 😟

cherry tree trunk closeup sap hole.JPG
cherry tree trunk070120.JPG
cherry leaf closeup.JPG
cherry tree leafless branches070120.JPG
Paula Mohr
Paula Mohr (@guest_8558)
Reply to  Helga George, PhD
6 months ago

Thank you for your reply, Helga. I reached out to the University of MN Extension Master Gardener program and that person thought it might be gummosis (sent the same pics) and suggested sending in a sample to the university lab for diagnosis to be sure. Also, she didn’t think the tree could be saved. I’ll see if there is a local arborist… Again, thanks!

Vitória (@guest_8688)
6 months ago

Hi, I saw this blog and found it useful for this problem. I have two grafts with gummosis, unfortunately, today I killed the orange tree because of this disease. The other foot, of tangerine, is infected, it has a more or less thick trunk, it is still new. I haven’t decided if I should get rid of it too, since small breaks in the trunk are spewing gum, and around the bark it is brown in color. It is close to the root. Is there a method to save the foot I love so much? I’m sad about it, I’ve… Read more »

Ijaz Ahmad
Ijaz Ahmad (@guest_8782)
6 months ago

I have gummosis on fruits of peach not on trees.
What I have to spray in fungicide?

Aron (@guest_8917)
6 months ago

Hi , not sure if this thread is active still but is there anything I can do to stop mine from oozing?

Aron (@guest_8918)
Reply to  Aron
6 months ago

Here’s another pic

Vijay Challa
Vijay Challa (@guest_9101)
5 months ago

Just noticed this today and I see sap oozing from a few places in my nectarine tree, including the trunk. It seems to have just started. Is there anything I can do to help the tree? We love our tree! Thank you!

Bianca Decu
Bianca Decu (@guest_9224)
5 months ago

Hello! I think my Cherry tree has gummosis as well! Do you think I can still save him!? Help!! What should I do with my tree? What should I buy to make him better please!!?? Thank you!

Craig (@guest_9326)
5 months ago

Hi Helga, I would like to start by thanking you for helping so many people with their problems. I can see that unfortunately, I’m not alone here. Please see photos attached of my cherry, peach and nectarine. They are in raised beds above clay but I fear they have been overwatered this winter here in Tasmania, Australia. Possibly waterlogged for several months. It has been cold and wet for months where they are growing, with possible exposure to multiple frosts. Last winter I didn’t water the trees at all and some of the soil got very dry and crusty. This… Read more »

Craig (@guest_9379)
Reply to  Helga George, PhD
5 months ago

Thank you so much Helga! That Pennsylvania State University article was very informative. I will attempt surgery to remove the cankers as soon as we have a forecast of dry weather. This could be quite a wait! I noticed the cankers were oozing a lot of gum today after we have just had three days of rain. I had taken some scion wood and stored in the fridge for my father to graft onto his nectarine. I’m guessing this is a bad idea as it may transfer the disease to his orchard. The scion wood appears healthy, but I guess… Read more »

Gulab (@guest_9645)
4 months ago

I want to know how to control gummosis diseases in stone fruit

Adam Wertz
Adam Wertz (@adam-wertz)
Reply to  Gulab
4 months ago

Did ya read the article? That’s what it’s about.

Volodymyr Mykhaylyuk
Volodymyr Mykhaylyuk (@guest_9735)
4 months ago

Good article, thanks. If it is the fungus it will probably kill my appricot tree, as I noticed gummosis all around the trunk 🙁

Jessica (@guest_9785)
4 months ago

Hi, i see that my peach tree is presenting the symptoms of gummosis but I can’t tell if it is caused by fungus or not. I don’t see any black pimples as you said. But the tree is dying at an alarming rate (more than half has died in just one month). One of the arborists I spoke to said it might be fungus and that it could spread to the other trees in our yard (Mulberry and Italian Cyprus). Could that be true? (they also mentioned that it could be nearby Oleander poisoning the roots which I have read… Read more »

Juan Hernandez
Juan Hernandez (@guest_9861)
4 months ago

Good evening Doctor, it was with great dismay that I discovered Gum and separating bark at the bottom of my orange tree, I know that a diagnosis from a couple of pictures is difficult but if you do not mind, would you please look at these and see what you think what the cause might be? Also, how to treat?

Orange tree, wood behind separated bark.jpg
Orange Tree base with Gum.jpg
Carolyn Jones
Carolyn Jones (@guest_9923)
4 months ago

Hi Helga – thanks for putting together such a useful blog! I recently moved into a new house in Oregon with a very sad cherry tree in back. I noticed sections where it looks like the previous owners may have extensively pruned which now have various knobs of new growth surrounded by amber and clear gummosis. The tree is really not growing well and I can’t even identify any non-affected sections! The worst gummosis is around the trunk and most of the leaves are full of holes. Do these look like cankers to you? I’d like to try something but… Read more »

trunk knob.png
Eric Scharf
Eric Scharf (@guest_10481)
2 months ago

We have what I believe is a flowering Cherry and it started the sap near the base of the trunk and I recently removed it and put some protective paint over it, but it’s still oozing in some small spots. Do I actually take a knife and carve back the bark a little or what’s recommended? And then I’d assume I’d retreat the area again after exposure and letting it dry a little… Southern AZ at 4,800 elevation

Jamie Smith
Jamie Smith (@guest_10657)
2 months ago

Is it possible to introduce a different fungi that will benefit the trees and fight off the damaging fungi?