Is this disease or something with the roots ?

This shrub is actually two growing together side by side - almost like connected...they have been growing for years and looked healthy until about 2-3 months ago when I repaired the grass and started to water the yard daily.
I was guessing it was just too much water BUT..... seems only one is being affected and still getting worse week by week, even though I had stopped watering my new grass (it's looking nice and healthy) .... so I wonder if maybe the roots got rotten or something and maybe this isn't a diseases ???

Anyhow.... should I know just saw it off at the base ?
Don't think it will recover at this point.... the progression was rather slow... first just a few spots and it took about 3 months to get to this point....

Please let me know if removing that part is the right move and if there is anything I should be watching out for...

Thank you !

 

I would just cut the dead tree off near it's base. The other one should slowly fill in over time.

 

thank you - BTW.... would you associate similar damage to plants, including evergreens like small pine tree due to spraying with insecticides like Talstar ??

I can take more pictures, but I have multiple shrubs and small trees that are showing some yellowing and drying... nothing as extreme as the one already pictured.... but it worries me and really have no idea why they all are showing this....I have lived here for 5 yrs now and everything looked good until late this Summer.
The only thing I have done "differently" that I can think of - is spraying about twice a month with a few residual insecticides

 

I've only applied Talstar underground for termites. I've never sprayed it on shrubs and trees but since that is one of it's approved uses I don't think it would cause any problems.

I would suspect root rot or some fungal disease. You had two trees growing together so they are already stressed. Add to that daily watering and it's a good situation for root rot.

 

thanks again... .worry that this actually may be something systemic happening in my backyard.
Another picture showing similar issue - this one is in the same line of plants growing along the mulch line

 

why do my pictures get rotated ??
I see them as upright on my computer before uploading ?