I have a line of arborvitae trees running down our fence line that were planted 3 years ago to block an apartment complex. This year random spots began turning yellow then they turn brown in the middle of the yellow areas. I have sprayed them with fungicide(deconil) twice at one week intervals, then neem oil a week later and they are not getting any better. The coloring started at the lower portions of the shrubs but is now moving up the shrubs in areas. The front yard is doing this, however the back yard shrubs only have small spots of this discoloration like the front nothing huge though. We recently pulled all of the sod up in the back yard 3 months ago to rock(rock is not down yet) so the ones in the back are no longer being watered by the sprinkler system we have they have a drip line we turn on when needed(the front does too but is mainly watered by the sprinklers). I immediately thought it has to have something to do with the sprinklers because the back was not doing this so 3 weeks ago I had my husband move the sprinkler out 3 feet in the front yard from the shrubs so they don't get hit. Before they were directly getting hit by rainbird sprinkler heads that turn a complete 180 and shoot down the entire line of arborvitaes hitting half way up the tree. Nothing seems to be working and I am afraid of root rot? Could this be like a sunburn maybe? We also have a weeping cedar that is now getting brown beaches as well out front. Please help!!!!

Anytime there is a strong change in environmental or management conditions, plants are going to react in some fashion. Noted changes include removal of sod (changing the soil environment the arb roots are growing in, the water supplied has changed (If the water has always been supplied the plants may now be lacking sufficient roots to remove water deeper in the soil profile). You mention putting down rock later. i would consider an organic mulch over inorganic. Much better as it decomposes and returns nutrition to the plants. Digging a small vertical hole and accessing soil moisture will into the ground will tell you if these plants are being over watered. Using a dry wooden dowel rod pushed into the profile may be another way. comes out dry, may need to water, comes out dark, wet, muddy it is too wet. If your root rot theory is correct, the fungicides and oils applied to the needles will not help in this case. Suggest you contact your local extension office for a more focused and local response. Illinois is too far away to account for your local conditions.