Problems with Plum Tree Leaves - Ask Extension
Hi, We have a multi-graft plum tree in our yard that has had leaf problems for two years now.
The leaves on many branches have holes in them and/or ...
Knowledgebase
Problems with Plum Tree Leaves #654665
Asked June 22, 2020, 5:53 PM EDT
Hi, We have a multi-graft plum tree in our yard that has had leaf problems for two years now.
The leaves on many branches have holes in them and/or emerge crinkled and die soon after emergence. This has left some of the branches on the tree nearly bare. There are spots on some of the fruit as well. We have sprayed with some Dr. Earth anti-fungal and anti-insect after we saw the problem happen again this year. We understand though that it might be too late. In any case, we wanted to send pictures and ask for advice as to what we should do going forward to prevent this problem occurring again in this tree. Thank you for your help!
Benton County Oregon
Expert Response
This could be a number of factors. Do you water the trees regularly during the summer months? Over watering or over fertilization can cause leaves to die and drop, as can drought stress. Have any herbicides been used around the tree recently? Herbicide damage can also result in dry desiccated leaves. Do you see any symptoms on the flowers? What do the spots on the fruit look like? Do you see any cankers on the trunk or branches of the tree? Is there any sap like material oozing from the trunk or branches?
Based on the information provided, my best guess is that this may be Bacterial canker. Bacterial canker can cause die back of infected branches (https://pnwhandbooks.org/plantdisease/host-disease/prune-plum-prunus-spp-bacterial-canker and http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/baccanker.html). Phytophthora can also cause die back, but I would expect all branches to be affected in this case since this is a soil borne pathogen (http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/pchphytoph.html). The holes in the leaves could be caused by an insect with chewing mouth part or it could be Shothole fungus (https://pnwhandbooks.org/plantdisease/host-disease/prune-plum-prunus-spp-leaf-spots). With Shothole you would see purplish-brown spots on the leaves that would enlarge and eventually the center would fall out leaving the appearance of a shot hole.
If this is canker and/or shothole, I suggest raking up and destroying all fallen leaves and fruit this fall. If you do see cankers or gummosis on any of the branches, prune out the infected plant parts in January or February. In the fall, around the time of leaf fall, spray a copper based fungicide followed by a second application in January. Then continue to monitor the tree for symptoms and repeat these practices next year. If this is in fact Phytophthora and not canker, or if the tree is already severely infected, it may not recover.
Based on the information provided, my best guess is that this may be Bacterial canker. Bacterial canker can cause die back of infected branches (https://pnwhandbooks.org/plantdisease/host-disease/prune-plum-prunus-spp-bacterial-canker and http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/baccanker.html). Phytophthora can also cause die back, but I would expect all branches to be affected in this case since this is a soil borne pathogen (http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/pchphytoph.html). The holes in the leaves could be caused by an insect with chewing mouth part or it could be Shothole fungus (https://pnwhandbooks.org/plantdisease/host-disease/prune-plum-prunus-spp-leaf-spots). With Shothole you would see purplish-brown spots on the leaves that would enlarge and eventually the center would fall out leaving the appearance of a shot hole.
If this is canker and/or shothole, I suggest raking up and destroying all fallen leaves and fruit this fall. If you do see cankers or gummosis on any of the branches, prune out the infected plant parts in January or February. In the fall, around the time of leaf fall, spray a copper based fungicide followed by a second application in January. Then continue to monitor the tree for symptoms and repeat these practices next year. If this is in fact Phytophthora and not canker, or if the tree is already severely infected, it may not recover.
