Posted: 29/07/2013 at 08:15
Laurel can be vulnerable to powdery mildew and your grey covering sounds very typical. The leaves will curl in as the tissue dies. Am assuming you didn't find any bugs inside the curled up leaves?
powdery mildew is caused by overcrowding and plants suffering stress eg from being to dry. I suggest that you trim off the affected leaves to improve the appearance but don't prune to aggressively if is is rife as this will stress the plants more. Give thenm a good watering and mulch. You can get spray treatments for powdery mildew although not sure how effective these are once it's got a hold. The plants should survive and recover anyway anyway it's more unsightly than anything else. But a good feed and spray treatment at the start of spring next year should help prevent it. Also make sure you clean up any dropped leaves and bin these as they will be carrying the fungal spores.