What is wrong my cotoneaster? - Ask Extension
Despite much searching (including your site), I haven't been able to figure out what is hurting our cotoneaster. It doesn't appear to be any of the pr...
Knowledgebase
What is wrong my cotoneaster? #646880
Asked June 06, 2020, 10:31 AM EDT
Despite much searching (including your site), I haven't been able to figure out what is hurting our cotoneaster. It doesn't appear to be any of the problems commonly associated with the plant.
As can be seen in the attached image, dark spots appear on the leaves. As they expand, dead grey leaf is appears within the spot. This continues until the entire leaf is dead and grey. It appears to spread to the branches as well although there is new growth on them - but not much and it is not what I would call hardy. The underside of the leaves look about the same as the top and I do not see evidence of parasites.
We planted about 8 years ago and since it has spread, do some overhead watering in late summer if it gets really dry and have not fertilized.
I would like to know what is causing this and would appreciate recommendations on how to bring our cotoneaster back to health.
Let me know if I can provide more information and thanks in advance for the help.
As can be seen in the attached image, dark spots appear on the leaves. As they expand, dead grey leaf is appears within the spot. This continues until the entire leaf is dead and grey. It appears to spread to the branches as well although there is new growth on them - but not much and it is not what I would call hardy. The underside of the leaves look about the same as the top and I do not see evidence of parasites.
We planted about 8 years ago and since it has spread, do some overhead watering in late summer if it gets really dry and have not fertilized.
I would like to know what is causing this and would appreciate recommendations on how to bring our cotoneaster back to health.
Let me know if I can provide more information and thanks in advance for the help.
Thurston County Washington
Expert Response
Believe it or not, this looks like the apple scab fungus--the same one that causes those corky rough spots on apples. It also affects cotoneasters. This may be very difficult to control on cotoneasters because the leaves are so tiny. One of the most important management practices is to pick up and destroy all diseased leaves. Perhaps a leaf vacuum. Fungicides can be used in conjunction with this sanitation measure. Treat in spring when you see buds of new growth beginning to form. Treat again when the shrub has its new leaves. For more details: http://hortsense.cahnrs.wsu.edu/Search/MainMenuWithFactSheet.aspx?CategoryId=1&SubCatId=4&PlantDefId=8&ProblemId=338
Thank you very much!
