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.

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.

We link to vendors to help you find relevant products. If you buy from one of our links, we may earn a commission.

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.

Close up of gummosis on an apricot tree trunk.

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.

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.

And for more information on growing fruit trees, check out some of our other guides:

© 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.

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)
1 year ago

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

Lauren Maier
Lauren Maier (@guest_5870)
1 year 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)
1 year 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)
1 year 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
1 year ago

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

Paul Hartshorn
Paul Hartshorn (@guest_10553)
Reply to  Helga George, PhD
10 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
10 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
1 year 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
1 year ago

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

Anu (@guest_11993)
Reply to  Rick Perkins
4 months ago

I have similar issue. Did you find any solution? Thanks

Gabriel Diaz
Gabriel Diaz (@guest_6387)
1 year 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
1 year 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)
1 year ago

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

Abe C.
Abe C. (@guest_7369)
1 year 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)
1 year 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)
1 year 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