Last year I had a Tree Pruning Company trim my cedar hedge this year the hedge is turning brown I do not know if it was poisoned by leaking gas (trimmer) or salt damage or by insect, the area is erratic in shape the back side is not as bad any help would be greatly appreciated
There is a total of 240 ft of hedge ranging from 7ft to 16ft high. I have had these hedges for close to 38 years.
Thank you for contact Toronto Master Gardeners.
The damage in the picture does look localized. If you had insect or disease issues I would expect a more generalized damage. Any number of things could cause this issue. As you say something spilled or salt spray could damage the leaves. Has there been any spraying nearby on the lawn or other plants? has there been any digging that could have affected roots?
The best thing you can do is give the plants the healthiest environment possible and hope for new growth in the area. I am attaching one of our many articles from our library that talks about cedar care. If you search our library you will find many more.
During this heat do make sure you water the affected plants deeply when the soil dries out.