canker on fruit tree - Ask Extension
On the trunk of a small plum tree there is a canker. I cut it off and wonder if it has likely spread into the tree above where it was. Branches above ...
Knowledgebase
canker on fruit tree #670441
Asked July 29, 2020, 3:56 PM EDT
On the trunk of a small plum tree there is a canker. I cut it off and wonder if it has likely spread into the tree above where it was. Branches above it are not doing as well as branches that are below it. Will the fungus kill the tree or just keep it from growing normally?
Dorchester County Maryland
Expert Response
Are you able to share photos of the tree overall plus the ailing branches that were above the canker? What did the canker look like - was it sunken and darkened or raised, knobby, and black? Is this a fruit-bearing plum or an ornamental plum with purple summer foliage and light pink flowers in the spring? These answers and photos will help us to determine what the issue may be.
Miri
Miri
Miri
This is a fruiting plum tree- Santa Rosa. It was planted 3 summers ago from a bare root tree sent from Stark Bros. I have include photos of where the canker was. I carves it out down to the clean wood. Also have photos of lower part of the trunk, leaves on branches above the canker and leaves on branches below the canker. Those branches are growing well this summer while the others are stagnant. no shoots with new leaves. Is it likely that the knobs on the lower part of the trunk also contain fungus? If not then would cutting the tree off below the known canker lead to the tree producing strong enough branches to produce a viable tree?
I have 2 other trees that are as young and not doing great also. I will send another response with photos of those.
David
This is a fruiting plum tree- Santa Rosa. It was planted 3 summers ago from a bare root tree sent from Stark Bros. I have include photos of where the canker was. I carves it out down to the clean wood. Also have photos of lower part of the trunk, leaves on branches above the canker and leaves on branches below the canker. Those branches are growing well this summer while the others are stagnant. no shoots with new leaves. Is it likely that the knobs on the lower part of the trunk also contain fungus? If not then would cutting the tree off below the known canker lead to the tree producing strong enough branches to produce a viable tree?
I have 2 other trees that are as young and not doing great also. I will send another response with photos of those.
David
Miri
This is about an apple tree. Since I can only do 3 photos per response the next will be about the pear tree.
This tree is 2 years in the ground from Lowes as a potted tree. At is base is a growth that might be a canker. There is a photo of that. Then 2 photos of leaves. Most of the leaves are are like the photo with the dark spots and eaten sections. the other photo show the only place there is clean new growth. I have used Neem oil spray through the spring then one spraying of Sevin 2 weeks ago. Is that knob at the base likely to be a canker or something else that has set back this tree.
David
This is about an apple tree. Since I can only do 3 photos per response the next will be about the pear tree.
This tree is 2 years in the ground from Lowes as a potted tree. At is base is a growth that might be a canker. There is a photo of that. Then 2 photos of leaves. Most of the leaves are are like the photo with the dark spots and eaten sections. the other photo show the only place there is clean new growth. I have used Neem oil spray through the spring then one spraying of Sevin 2 weeks ago. Is that knob at the base likely to be a canker or something else that has set back this tree.
David
Miri
Now the pear tree. Planted 3 summers ago. A bare root tree from Stark Bros. It produces leaves in the spring and no new branching growth with new leaves. It has a bunch of knobs on its trunk which are shown in a photo. There is another knob in the middle of the trunk. then a photo of leaves. Are those lower knobs also canker? Is this tree stunted by them or something else?
David
Now the pear tree. Planted 3 summers ago. A bare root tree from Stark Bros. It produces leaves in the spring and no new branching growth with new leaves. It has a bunch of knobs on its trunk which are shown in a photo. There is another knob in the middle of the trunk. then a photo of leaves. Are those lower knobs also canker? Is this tree stunted by them or something else?
David
Thank you for the photos David.
Plum: except in rare cases, removal of infected growth should not cut into the trunk itself, as it removes tissues needed to seal-off the wound from infection and insect attack. For the future, a canker is best removed by pruning it out entirely, not carving out only the visible portion. (This is why trunk cankers are more problematic than branch cankers.) For now, wait and see how the tree responds, because some of its vascular tissue (what moves water and nutrients around) has been lost and part of the root system or canopy may die back as a result. There is nothing else to do at this point; either the tree will recover (or at least not decline) or it will succumb. If it succumbs above the wound, cut it back with a pruning saw to just below this point and you will have to select new side branches to eventually become the fruiting stems.
To answer your original question about spread, some infections will have already spread beyond the visible symptomatic tissue (in this case, a canker), so removing only this area may miss the rest of the pathogen. We do not know which exact disease caused that canker so the future health of the tree is uncertain. That said, canker diseases are often damaging and can lead to tree death if too much of the trunk is compromised.
Apple: This looks less like a canker and more like the graft union and/or a sucker that was removed. Sucker removal is important and good to do; graft unions should not be buried too deeply, which this appears to be, as they normally are kept several inches above the root flare (where roots begin to branch off of the trunk, a spot that is supposed to sit just at/below the soil surface). It's not uncommon for trees to become buried too deeply in their pots, so gentle excavation to find the root flare is helpful when planting.
The leaf spotting and holes are likely a combination of disease (like apple scab) an d relatively minor insect feeding. Pests do not require control at this point and it is too late this season to spray for diseases. Neem and Sevin can be effective insecticides but it's best to identify a specific pest problem first in order to know how best to treat it (when, how, and with what chemical). Sevin can cause more unintended harm than Neem by killing beneficial insects which may be trying to control a pest population. Neither will have any affect on fruit tree diseases.
Pear: The trunk knobs may be old cankers or merely old physical injuries, such as from cicada egg-laying scars. The old injury above the graft union (the kink low on the trunk) is more serious given how much inner wood is exposed, though it is at least calloused-over now, which is a normal reaction. This tree also has a type of leaf-spot disease, though we cannot discern which. Here too, treatments are not needed at this time. Stunting and lack of vigor are probably root-related, assuming the tree receives good light (6+ hours of sunlight a day in summer). Check regularly for moisture needs, make sure the base is mulched to avoid lawn equipment injury, and make sure deer don't frequent the area.
Here are watering tips for trees and shrubs: https://extension.umd.edu/hgic/topics/watering-trees-and-shrubs
Here is info. on deer and a picture of antler rubbing, a fall phenomenon which can cause serious damage to young unprotected trees: https://extension.umd.edu/hgic/topics/deer
This is a page on how to prune trees, with general tips on how and where to make cuts: https://extension.umd.edu/hgic/topics/pruning-trees. For fruit trees, any specific pruning style (such as how to train branches for ease of harvest and good airflow) should refer to information in the pages linked below, since their training is different than that of typical flowering and shade trees. (How to make a pruning cut is a universal matter.)
Here are pages on plum, apple, and pear general care and troubleshooting:
https://extension.umd.edu/hgic/topics/stone-fruit-peaches-cherries-plums-apricots-nectarines
https://extension.umd.edu/hgic/topics/apples
https://extension.umd.edu/hgic/topics/pear
A link to pest and disease control measures, when it involves pesticide sprays, is included in a link on each pest/disease page. Fruit trees are very high-maintenance, but learning about their care needs and recommended preventative spray programs will save a lot of time and lost crops down the road.
Miri
Plum: except in rare cases, removal of infected growth should not cut into the trunk itself, as it removes tissues needed to seal-off the wound from infection and insect attack. For the future, a canker is best removed by pruning it out entirely, not carving out only the visible portion. (This is why trunk cankers are more problematic than branch cankers.) For now, wait and see how the tree responds, because some of its vascular tissue (what moves water and nutrients around) has been lost and part of the root system or canopy may die back as a result. There is nothing else to do at this point; either the tree will recover (or at least not decline) or it will succumb. If it succumbs above the wound, cut it back with a pruning saw to just below this point and you will have to select new side branches to eventually become the fruiting stems.
To answer your original question about spread, some infections will have already spread beyond the visible symptomatic tissue (in this case, a canker), so removing only this area may miss the rest of the pathogen. We do not know which exact disease caused that canker so the future health of the tree is uncertain. That said, canker diseases are often damaging and can lead to tree death if too much of the trunk is compromised.
Apple: This looks less like a canker and more like the graft union and/or a sucker that was removed. Sucker removal is important and good to do; graft unions should not be buried too deeply, which this appears to be, as they normally are kept several inches above the root flare (where roots begin to branch off of the trunk, a spot that is supposed to sit just at/below the soil surface). It's not uncommon for trees to become buried too deeply in their pots, so gentle excavation to find the root flare is helpful when planting.
The leaf spotting and holes are likely a combination of disease (like apple scab) an d relatively minor insect feeding. Pests do not require control at this point and it is too late this season to spray for diseases. Neem and Sevin can be effective insecticides but it's best to identify a specific pest problem first in order to know how best to treat it (when, how, and with what chemical). Sevin can cause more unintended harm than Neem by killing beneficial insects which may be trying to control a pest population. Neither will have any affect on fruit tree diseases.
Pear: The trunk knobs may be old cankers or merely old physical injuries, such as from cicada egg-laying scars. The old injury above the graft union (the kink low on the trunk) is more serious given how much inner wood is exposed, though it is at least calloused-over now, which is a normal reaction. This tree also has a type of leaf-spot disease, though we cannot discern which. Here too, treatments are not needed at this time. Stunting and lack of vigor are probably root-related, assuming the tree receives good light (6+ hours of sunlight a day in summer). Check regularly for moisture needs, make sure the base is mulched to avoid lawn equipment injury, and make sure deer don't frequent the area.
Here are watering tips for trees and shrubs: https://extension.umd.edu/hgic/topics/watering-trees-and-shrubs
Here is info. on deer and a picture of antler rubbing, a fall phenomenon which can cause serious damage to young unprotected trees: https://extension.umd.edu/hgic/topics/deer
This is a page on how to prune trees, with general tips on how and where to make cuts: https://extension.umd.edu/hgic/topics/pruning-trees. For fruit trees, any specific pruning style (such as how to train branches for ease of harvest and good airflow) should refer to information in the pages linked below, since their training is different than that of typical flowering and shade trees. (How to make a pruning cut is a universal matter.)
Here are pages on plum, apple, and pear general care and troubleshooting:
https://extension.umd.edu/hgic/topics/stone-fruit-peaches-cherries-plums-apricots-nectarines
https://extension.umd.edu/hgic/topics/apples
https://extension.umd.edu/hgic/topics/pear
A link to pest and disease control measures, when it involves pesticide sprays, is included in a link on each pest/disease page. Fruit trees are very high-maintenance, but learning about their care needs and recommended preventative spray programs will save a lot of time and lost crops down the road.
Miri
