My cedars are 10 years old and have had no issues until this year when I noticed yellow patches in the tallest tree. When I went to prune these yellow patches I also noticed some strange whitessack-material on the some of the branches. Is the tree dying?
Hello – Your cedars look very healthy in your photo so I don’t think the tallest one is in danger of dying anytime soon. Browning on cedars is unfortunately very common and can be caused by a number of factors.
Cedars are moisture loving and the stress of too little water can cause the browning you are seeing. Cedars must be kept watered right up till our hard freeze in order to have enough moisture to see them through the winter.
Cedars do not like road salt and can be damaged by splash from nearby roads and sidewalks.
They do not tolerate shade – has the shade in your yard increased over the 10 years?
Finally, they can also be damaged by animal urine particularly from dogs.
You mentioned that you have already pruned these yellow patches so I hope that has improved the appearance. As cedars will not grow new foliage on old wood, pruning can sometimes create holes. A suggestion is to shake off the dead foliage as it dries rather than cut out sections.
I am concerned about the ‘strange whitesack-material’ that you mention. Southern Ontario is expected to have a very large population of gypsy moths this season whose larva hatch from white or tan coloured fuzzy egg masses about the size of a loonie. Does this sound like what you are seeing? Cedars are not known to be particularly susceptible to damage from gypsy moth but in a year of high populations this could become an issue. I am including a link below to an article on the Ontario Nursery Crop blog on the gypsy moth. The article contains some good pictures of the egg cases. If the material on your cedars does not look similar to what you see in the article, please take some photos of the material on your trees and send our way.
Other Resources:
https://www.torontomastergardeners.ca/askagardener/emerald-cedar-browning-recovery/
https://www.torontomastergardeners.ca/askagardener/eastern-cedars-turning-brown/