Could be root damage - be that too much water or manual (digging in the area). Improving drainage will help with that, though quite how you prepare for the very wet summer we had is another question. There is an aphid that attacks Cypress but as it is not spreading I think it is drainage. Do you know what type of evergreen you have? Leylandi will not regrow but Cedar normally will.

The ones that are most badly affected are Pencil Pines, we have 250 Leylandi which are thriving, as are most other plants and shrubs in the garden. The problem hasn't affected other evergreens in the same area so I doubt improved drainage is the answer.

Thank you ever so much for your interest.

Regards Wendy.

There is a disease affecting conifers around the UK. I suggest the RHS website for more detail of name and treatment.....if any. Wow.... 250 Leylandii must be some sort of a record.

We planted them right along the length of a public footpath over one of our paddocks....they really are the best example of Anti-Social behaviour!!! Out of sight, out of mind! We rightly deserve an ASBO!
Thank you for your advice, I will refer to the RHS.

Could it have been sprayed with salt in winter/root level? Browning can take a while to show.

Nope! They are not anywhere near a road, or a salt mine or the ocean! (Or a fish and chip shop!) It's so sad, they were lovely trees and maturing nicely.

Thank you for your interest! Regards, Wendy.

We left 6 leylandii behind us at the bottom of a long garden after we sold some land we owned. They are are amazingly still there. That was ages before they became a source of litigation and arguments. They are massive now even though we cut them every year for around 18 years. They are not shading anything anyone cares about.