It's hard to determine the exact cause of decline from the photos, but possibilities include cumulative drought stress, scale insects, and peachtree borer, the latter of which tends to preferentially target Cherry Laurel shrubs already stressed by something else. (These evergreens don't wilt until they get excessively dry and are already water-stressed, so the early stages of stress won't be very symptomatic, and they also do not handle over-watering or poor soil drainage well.) You can explore our Cherry Laurel diagnostic page for more information about the typical ailments these shrubs can develop.

We don't see signs of scale on the bark, though the areas most associated with dieback aren't entirely visible. You can use the information in the page above plus our White Prunicola Scale page to look for their telltale white waxy covers adhered to the bark. They will be quite obvious if present and abundant, so if you don't see any centered around the dying branches, they aren't an issue.

You can look for indications of borers by examining the wood you prune off (all brown and dying branches need to be trimmed off, as they will not recover). Larvae of this borer tunnel into the wood and will leave a detectable hole, sawdust residue, and possibly also gummosis (sap ooze) from the bark around the gallery (tunnel). While you cannot treat borers with an insecticide once they are already inside the wood, preventative measures to boost the health of the shrubs can help prevent their return. Mainly, this centers around watering as needed during drought, like the one we are currently experiencing.

Even if you treat the shrubs the same in terms of irrigation, it's entirely possible that one individual in a group or row will struggle with over- or under-watering due to differences in soil texture or drainage, or a greater exposure to influences like drying winds or reflected heat from nearby walls, pavement, or stone.

The English Ivy groundcover is competing with the shrubs for moisture, though to be fair, any groundcover would to some extent. Still, as an invasive species, we encourage gardeners to remove it when possible.

Miri