Canker on little plum and peach trees - Ask Extension
Hi,
I am new to growing fruit trees. Last fall I saw sap oozing from a branch on my little plum tree (I didn't think much of it). This spring, I s...
Knowledgebase
Canker on little plum and peach trees #782397
Asked February 22, 2022, 2:23 PM EST
Hi,
I am new to growing fruit trees. Last fall I saw sap oozing from a branch on my little plum tree (I didn't think much of it). This spring, I see damage (sap, cuts) on most of the branches including the trunk of the plum tree. Researching it, I found it it was 'canker.' I am pretty sure the plum tree is done for because most of the branches and trunk are infected. Today looking carefully, I also saw damage/sap on the nearby little peach tree. I thought I could just prune off the infected branches but then I saw sap on the main trunk of the peach tree also. Do I need to get rid of both these trees or is there something else I can do. I'm afraid of it spreading to my little cherry and japanese apricot trees.
Thank you.
Trinh
Prince George's County Maryland
Expert Response
Hello Trinh,
Canker is a catch-all term for several causes of plant injury that causes this group of symptoms - oozing sap, sunken or raised tissue, and darkened bark. Fungi and bacteria are the main causes of canker infections, but it can be difficult to determine which species is responsible; we aren't able to concretely diagnose the exact cause from photos. Often, plants are more susceptible to canker after they have been experiencing stress from environmental conditions such as extremes of heat or moisture (like under- or over-watering), confined roots, or wounds from pruning cuts, bark damage, or other causes.
The trees in your photos appear to be in containers. If they are, we recommend they be planted in the ground for best health and productivity. You can do this any time the ground isn't frozen; this time of year, during a thaw, would be good. If you must keep them in pots due to lack of available yard space, use the largest pot you can manage and make sure the container has good drainage. A tree, even if a dwarf variety, will tend to have a more limited harvest due to lack of root room when grown in a pot compared to growing in the ground. Container soil also experiences more drastic temperature swings, tends to dry out faster, and can become nutrient-depleted faster than soil in a plant's root zone in the ground. We mention this because these are all factors that can make a plant more vulnerable to pests or disease over the long term, including canker and wood-boring insects (which can also cause sap oozing).
Unfortunately, canker is incurable if it is the cause of these symptoms; a fungicide application won't be effective. Diseased wood could be removed if it occurs on branches that you can trim off, but on a trunk, this is of course not an option. However, not all sap oozing is a sure sign of canker; some trees ooze sap (called gummosis) when under stress from a variety of causes.
We can't see any cuts on the branches you mentioned, but if they are located on twigs or small branches, they could be due to cicada egg-laying from earlier last year. In that case, just trim off any weakened wood. Some branches do "heal" well enough on their own that they won't die back from this type of injury.
The tree pictured in the "canker plum 1" photo has branches which are crossing over each other. These should be pruned to correct their growth, as bark can be rubbed-off over time and the wounds infected later. In general, all major branch growth should be directed outwards from the canopy, so sharp turns that criss-cross the canopy like this need to be removed.
We have several pages about growing your own fruit trees, including selection and care, disease prevention, pests to anticipate, environmental stressors, and other information. This collection of web pages is a good starting point to learn more about tree care, if you haven't already seen it: https://extension.umd.edu/resources/yard-garden/fruit/tree-fruit
For now, this may be a wait-and-see situation, as you won't know how much impact these suspected cankers will have until the trees resume growth in spring and early summer. If the foliage emerges normally and the gummosis stops, then the problem may have resolved itself. If branch dieback manifests, then yes, it may be prudent to discard the afflicted tree(s) if too much growth has been impacted, especially if dieback involves the trunk.
Your other trees are also in the same genus as the plum and peach (all are Prunus), and they are indeed vulnerable to several of the same ailments. That said, there is little you can do to protect them except to preventatively spray them with the appropriate pesticide as part of their routine care (if they are a fruiting cherry and apricot as opposed to just decorative flowering cherry/apricot). There are options for either organic or synthetic pesticides, but the latter are usually more consistently effective. Cherries and apricots typically need multiple preventative applications for the array of pests and diseases that could injure them. The VA Tech publication we link to in the fruit pages goes into detail about what treatments are recommended for each pest and disease common to these crops.
Miri
Canker is a catch-all term for several causes of plant injury that causes this group of symptoms - oozing sap, sunken or raised tissue, and darkened bark. Fungi and bacteria are the main causes of canker infections, but it can be difficult to determine which species is responsible; we aren't able to concretely diagnose the exact cause from photos. Often, plants are more susceptible to canker after they have been experiencing stress from environmental conditions such as extremes of heat or moisture (like under- or over-watering), confined roots, or wounds from pruning cuts, bark damage, or other causes.
The trees in your photos appear to be in containers. If they are, we recommend they be planted in the ground for best health and productivity. You can do this any time the ground isn't frozen; this time of year, during a thaw, would be good. If you must keep them in pots due to lack of available yard space, use the largest pot you can manage and make sure the container has good drainage. A tree, even if a dwarf variety, will tend to have a more limited harvest due to lack of root room when grown in a pot compared to growing in the ground. Container soil also experiences more drastic temperature swings, tends to dry out faster, and can become nutrient-depleted faster than soil in a plant's root zone in the ground. We mention this because these are all factors that can make a plant more vulnerable to pests or disease over the long term, including canker and wood-boring insects (which can also cause sap oozing).
Unfortunately, canker is incurable if it is the cause of these symptoms; a fungicide application won't be effective. Diseased wood could be removed if it occurs on branches that you can trim off, but on a trunk, this is of course not an option. However, not all sap oozing is a sure sign of canker; some trees ooze sap (called gummosis) when under stress from a variety of causes.
We can't see any cuts on the branches you mentioned, but if they are located on twigs or small branches, they could be due to cicada egg-laying from earlier last year. In that case, just trim off any weakened wood. Some branches do "heal" well enough on their own that they won't die back from this type of injury.
The tree pictured in the "canker plum 1" photo has branches which are crossing over each other. These should be pruned to correct their growth, as bark can be rubbed-off over time and the wounds infected later. In general, all major branch growth should be directed outwards from the canopy, so sharp turns that criss-cross the canopy like this need to be removed.
We have several pages about growing your own fruit trees, including selection and care, disease prevention, pests to anticipate, environmental stressors, and other information. This collection of web pages is a good starting point to learn more about tree care, if you haven't already seen it: https://extension.umd.edu/resources/yard-garden/fruit/tree-fruit
For now, this may be a wait-and-see situation, as you won't know how much impact these suspected cankers will have until the trees resume growth in spring and early summer. If the foliage emerges normally and the gummosis stops, then the problem may have resolved itself. If branch dieback manifests, then yes, it may be prudent to discard the afflicted tree(s) if too much growth has been impacted, especially if dieback involves the trunk.
Your other trees are also in the same genus as the plum and peach (all are Prunus), and they are indeed vulnerable to several of the same ailments. That said, there is little you can do to protect them except to preventatively spray them with the appropriate pesticide as part of their routine care (if they are a fruiting cherry and apricot as opposed to just decorative flowering cherry/apricot). There are options for either organic or synthetic pesticides, but the latter are usually more consistently effective. Cherries and apricots typically need multiple preventative applications for the array of pests and diseases that could injure them. The VA Tech publication we link to in the fruit pages goes into detail about what treatments are recommended for each pest and disease common to these crops.
Miri
