Why is My Apricot Tree Leaking Sap? Gummosis Causes & Cures

Have you noticed sticky sap leaking from your apricot trees? This ooze is gummosis, and it's a natural way for the tree to show that something is wrong. You may not need to intervene just yet, however. The first step is to figure out the root of the problem. Continue reading for a deep dive on gummosis in apricot trees, including how to diagnose the cause of the problem - and what to do about it.

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The first time I encountered gummosis on my apricot tree, my first instinct was to panic slightly. What was going on? The reality is, gummosis can be caused by almost anything, from innocuous things like a bump from a string trimmer to problems with pests or disease. So how do you figure out what the issue is?

A fever or bleeding tells us that something is wrong and that we need to heal. In the same way, gummosis is a symptom, not the problem itself. Gummosis is a common sight on all stone fruit trees because of their thin bark, which is prone to injury, but it could be seen on other trees as well. To fix the problem, first find the reason.

For the home gardener, it can be tough to identify the cause of an apricot tree's oozing. But, with the step-by-step guidance in this article, you can narrow down the possibilities and adjust your care from there. Learn the possible reasons for gummosis, how to identify the underlying cause, what to do about it, and best practices for preventing gummosis in the future.

How to Identify the Cause of Gummosis

What is gummosis? Gummosis is when a tree releases a sticky, viscous substance from an injury or canker. It looks like a thick, gummy sap, and it can vary in color from clear to amber to dark brown. Gummosis is especially common in stone fruit trees within the genus prunus, including peaches, cherries, and - you guessed it - apricots.

Curious about any garden-related terms? Click on a highlighted word in the text, or visit The Fruit Grove Glossary to find out more.

Observe the tree closely using the following list to identify the gummosis cause. As you inspect the gumming and the tree itself, keep a bottle of isopropyl alcohol nearby to sanitize tools and prevent any infection from spreading. Use a sharp knife and/or a tool such as a large screwdriver to carefully scrape away the gum (I would avoid using any regular pruning tools).

  • Observe the location of the gumming. Is the tree oozing at the base of the trunk, at branch crotches, or at points along a branch? Is it isolated to one spot, or do you see gumming in many places?
  • Look at the sap itself. Is it clear, amber colored, or dark brown? Do you notice little bits of sawdust or bark trapped in the gum? Is it in big patches or coming out of small holes?
  • Look for evidence of injury. Is the gumming coming out of a scratch or cut in the bark? Or does it look like it's oozing from a sunken lesion rather than one specific spot?
  • Carefully scrape away the gum and outer layer of bark with a sharp, sanitized knife. Is the area underneath the outer bark light colored? Or is it tan, brown, or discolored in any way?

Use these observations to narrow down what might be causing the gummosis. Refer to the flow chart below to help, as well as the information below. I put together this chart based on several trusted sources, which I have also linked to in the next section. This chart is meant to be a starting point to help you pinpoint the root of the problem - for more specific information or help, I suggest contacting your local extension service.

Reasons for Apricot Tree Gummosis

Below are the common causes of gummosis in apricot trees, as well as what to do about them. I have also linked to helpful resources for more details. Once you have observed the tree, use the descriptions below to help determine what the culprit is - and how to prevent and/or treat the problem. In many cases, the best course is to leave the tree to heal itself and take steps to prevent further issues.

Mechanical Injury

The thinner bark of stone fruit trees makes them susceptible to scratches and cuts. If there has been damage to the bark, you may notice sap oozing from the spot. This particularly happens in the spring when the sap begins to run, but it could happen any time. When gummosis is caused by mechanical injury, the sap will be clear and may darken slightly as it hardens.

This type of injury can be caused by just about anything: hail damage, rodent scratches, lawn mowers, string trimmers, or even pruning. An apricot tree can ooze sap from fresh pruning wounds, particularly if it's pruned in early spring.

What to Do About It:

In general - nothing! Ensure that the tree is healthy, and it will heal itself. Always use sharp, sanitized pruning shears to leave the cleanest pruning wounds possible, and don't prune in wet weather. Take care when mowing or trimming around younger fruit trees, in particular, as the bark is very thin and tender.

Whenever I notice damage to the bark of my apricot tree (or other fruit trees), I use IV Organics 3-in-1 Plant Guard to preventatively seal the spot. This product repels pests, protects from sunscald, and has anti fungal and antibacterial ingredients. It's a great all-around product to have on hand in the garden - highly recommend!

This straight line of holes on my apricot tree came from a woodpecker. A little bit of gummosis is oozing from the holes.

Environmental Stress

An apricot tree stressed by weather or improper care may also begin leaking sap. If the tree is planted too deeply, for example, you may notice gummosis as a response to that stress. Proper planting depth is with the top of the root ball right at soil level - any deeper and the tree may struggle to thrive.

Apricot trees hate soggy, waterlogged soil. If drainage is a problem, the tree may ooze gum to try to regulate moisture (and to let you know that something is wrong). On the other hand, prolonged periods of drought may also lead to gummosis, again as a stress response. I experienced this issue with my apricot tree - fluctuating moisture levels can cause the bark to crack, leaving leaking wounds.

Overpruning can also cause gummosis, as can overbearing. A tree that has carried a heavy load of fruit the year before may be weakened, which can lead to gummosis. All of these issues amount to stress. Just like with people, the tree will exhibit signs of stress (gummosis, wilting, stunted growth) until the problem is addressed.

What to Do About It:

If irrigation is the issue, double check that the tree isn't being overwatered. It can be difficult to adjust soil drainage once a tree is established and grown to a mature size, but adjusting the amount of irrigation may be enough to make a difference. If the tree is in lean, sandy soil (as mine is) with very quick drainage, you may need to water more frequently and/or more deeply, especially in periods of drought.

Learn more: Soil Drainage for Fruit Trees: Everything You Need to Know

When pruning, aim to remove no more than 25-30% of the growth. Too much pruning can cause the tree to go into shock, or to grow too vigorously to try and make up for the lost canopy. Either way, stress may trigger gummosis. You can also prevent overbearing by thinning the apricots when they are young. If you suspect the crop is too big, remove some young fruit so that they are spaced about 4-6 inches apart on the tree.

Learn more: All About Pruning Apricot Trees: Why, When, & How to Do It

Boring Insects

The greater peachtree borer will tunnel into the bark of the tree to lay its eggs, which then hatch to become larvae. The larvae then feed on the tissue under the bark, causing the tree to ooze gum. This pest typically feeds at the base of the tree near the soil line, so if you notice thick, brownish gumming at the base of the trunk it may be due to these boring pests.

Other boring insects, such as flat or shothole borers, behave similarly. These smaller pests also tunnel into the bark, but the damage will look like tiny holes scattered over a branch - like shot holes - with sap oozing out.

Both of these pests are much more likely to attack a tree that is weakened by stress, particularly drought stress, sunscald, or other environmental stress. A healthy tree will send out lots of sap to try and get rid of the larvae, which may even kill them if the infestation is mild. The gummosis will have noticeable sawdust, bits of bark, or insect frass mixed into it.

What to Do About It:

If you see damage by boring insects, chances are the tree was already under stress because of some other issue. Check for over- or under-watering, nutrient deficiencies, planting depth, or other cultural care problems. Poke a piece of wire into the holes to try and kill the larvae. In late winter, spray the tree with a dormant oil (I use Monterey Horticultural Oil) to suffocate overwintering insects.

Some sources recommend using Spinosad (organic) and/or Permethrin to prevent boring and kill larvae. Always use these products as directed!

Fungal Infection

One of the most common reasons for apricot tree gummosis is a fungal infection called cytospora canker (also called perennial canker). The fungus overwinters on dead twigs and branches, then makes itself known in spring. It appears as larger darkened areas on the tree oozing with amber or brownish sap. The bark underneath the gum will be tan to dark brown.

Cytospora canker kills the wood under the gummosis, which can girdle and kill the branch above the spot. You may also see blackish spots called pycnidia all over the affected bark. Prolonged warm, wet weather in spring is the ideal condition for the spread of this disease. It's also more likely to occur if the tree is pruned in wet weather, or shortly before a rain.

What to Do About It:

The first step is to reduce stress on the tree, just as with the other causes of gummosis. A weakened tree is much more likely to succumb to a fungal infection. Overwatering or slow-draining soil are particular culprits, especially if the temperatures are high.

Prevention is the best course of action. Before planting, choose a disease-resistant apricot variety. Plant in well-draining soil and water and fertilize adequately. The most important thing, perhaps, is to prune only in dry weather. Take care to sanitize pruning equipment carefully to avoid spreading any infection. Also protect the tree from other bark injuries.

Learn more: Simple Ways to Clean and Maintain Your Pruning Tools

Unfortunately, there aren't any proven chemical treatments for cytospora canker. Prune and dispose of any infected branches and twigs. If the infection is very bad, or if it's on the trunk of the tree, the best option is to remove the tree. See the fact sheet below from Colorado State University for more details on recognizing and controlling cytospora canker.

Cytospora Canker Fact Sheet - Colorado State University Extension

Bacterial Canker

Bacterial canker (also called sour sap, spur and twig blight, or blossom blast) can look similar to cytospora canker at first glance, but with a few key differences. This infection is common on already weakened trees, and affects leaves and twigs in addition to branches. The disease first appears in spring, particularly when there is cool, wet weather after the blooming period, when infected young twigs die back. Leaves may develop small brown spots that later become tiny holes (shot holes).

Gummosis from bacterial canker looks darkened and often happens at the base of buds. On the trunk or larger branches, the dark cankers may extend longer along the branch. A key distinction of this disease is the smell - the bacteria makes the gummosis smell sour or fermented - like the smell of beer.

In the case of my apricot tree, the gummosis was caused by bacterial canker. I was sure of this because of the sour odor and the location of the gumming. The leaves of the tree also showed the spots and shot holes of a bacterial infection. Coupled with the extremely wet and mild spring we had, I knew I had found the culprit.

What to Do About It:

Bacterial canker often enters through pruning wounds or winter injury. Be sure to protect the trunk and large branches from sunscald with a product such as IV Organics 3-in-1 Plant Guard (or use white latex paint diluted 50% with water). Always sanitize pruning equipment and prune only when the weather is dry.

A healthy tree can better defend itself from bacterial canker and other diseases, or even recover if the infection is mild. Optimize cultural care of the tree, including watering (avoid planting in poorly drained soil), fertilizing, and pruning. It's also a good idea to remove any branches that are severely infected.

Thankfully, my tree was healthy and strong so it was able to recover from the infection. I cleaned the bark wounds before they got too bad by gently cutting away the canker and allowing the wound to dry out. I then sealed the wounds with the IV Organics Tree Guard (not essential, but I wanted to try and prevent the disease spreading). The tree had been stressed by a prolonged drought, so I adjusted my watering practices.

Bacterial Canker of Stone Fruit in the Home Fruit Planting - Penn State Extension

Bacterial canker on my 'Golden Sweet' apricot tree.

Eutypa Dieback

Gummosis may also be a sign of Eutypa dieback, a fungal disease that commonly affects grapevines as well as apricot trees. Twigs and branches will die quickly in the spring or summer, and there may also be cankers and amber-colored gum present. Eventually, the tree will become stunted, with fewer leaves and fruit clusters.

As with other fungal and bacterial diseases, the entry point for Eutypa dieback is commonly at pruning wounds. Pruning in wet weather (or just before) can easily introduce the fungus.

What to Do About It:

Cut back infected branches and limbs by at least a foot below the infection. Always prune in a period of dry weather. Pruning in summer after fruiting may help prevent Eutypa dieback (as long as the weather stays dry). Seal pruning wounds with a fungicide if you are concerned about wet weather.

Eutypa Dieback and Bot Canker - University of California

Preventing Gummosis on Apricot Trees

These are good cultural practices that will help prevent all of the above issues that lead to gummosis. To use a common saying, which is certainly true in gardening - an ounce of prevention is worth a pound of cure! (Especially if there is no surefire cure...)

  • Avoid injury from lawn mowers, trimmers, or other machinery.
  • Plant the tree in an area with good soil drainage.
  • Plant apricot varieties that are disease resistant and correspond to your hardiness zone and growing conditions.
  • Protect the tree from sunscald in the winter to avoid bark damage.
  • Keep the tree healthy and happy with good cultural care, including proper irrigation and fertilizing.
  • Prune diseased or dead branches. Never prune in or near wet weather. Always sanitize pruning equipment thoroughly.
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