Checking in to see if there is an answer yet. (8/29/19). Client brought in a sample of his Blue Spruce. He is concerned about black spots on the branches. If you look on the needles you can see small black dots. I was not here when he dropped the sample off. I called him and he said it was black "spots" on the branches. I had him send me a picture of what he was referring too. I am not sure what it is. There is Lichen on the branches, but that is not what his concern was. You can see in the one picture that I have circled what he was talking about. I have also sent a picture on the needles. He does have some die back on the lower branches and a few spots in the upper branches. These trees are lone standing on the west and northeast sides of his home. Do you have any idea? I appreciate your time. Thanks!
Sorry for the delay- volume of questions has been high all season!
The black spots could be galls caused by insects. A lab could open them and examine them under magnification to see if this is the case.
The black dots on needles is some sort of needle cast disease. Again, magnification is required to tell which needle cast disease(s) involved. The first link below shows good magnifed pictures of the common diseases, and suggested treatments.
Blue spruce are growing here out of their natural range. Michigan’s humid weather encourages a number of needle cast and other diseases and pests. As a result at a certain age, usually when trees are mature, you see them decline from these issues. Some needle cast diseases can be reduced by multiple applications of fungicides each spring during the wet weather.
Here are some articles that discuss this-
For your client to get a precise diagnosis, there are two options:
1- submit fresh samples, a picture of the whole tree, and a picture of a diseased branch to https://pestid.msu.edu There is a modest fee for the service.
2- Hire a certified arborist, a professional who has taken training in care, diseases, pests and passed certification tests. He/she will come on site and give a complete diagnosis and a plant care plan. The arborist fee is reasonable, when compared to losing one or more trees. Find certified arborists by zip code here—-
Should your client be interested in alternative trees, here are some suggestions that are similar to blue spruce but are much hardier here.
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