Prunus Laur. "Otto Luyken"
Hi, I have many of these in my foundation planting and have lost one a few years ago. Now I see another one dying and noticed that it has white specks on its trunk/branches. I have enclosed a photo. What treatment will save it? Thanks!
From your photos it looks like white prunicola scale on the cherry laurel branches. This is a sucking insect that sucks plant cell contents from twigs and branches. This can cause dieback, which is usually preceded by leaf yellowing and premature leaf drop. In general when shrubs are stressed due to poor planting techniques, poor site conditions, and environmental issues, they can be susceptible to insect and disease issues. http://extension.umd.edu/hgic/plants/armored-hard-scale-trees-and-shrubs
Make sure the shrubs are not planted too deeply. Deep planting causes bark deterioration at the soil line which will eventually kill the plant. Cherry laurels grow best in partial shade in a well drained soil. Check the drainage in the area (they do not like wet soils and poor drainage), make sure mulch is no thicker than two inches in depth, and keep away from the base of the shrub. Boring insects can be attracted to excessive mulch around the base of plants.
Here is some information on control and is difficult. Prune out any dead or dying branches. Now you can use a soft brush to remove the scale covers. You can use a dormant horticultural oil to manage light infestations in the fall (November) when trees drop their foliage (as long as it does not freeze within 24 hours). Follow label directions.
In the spring - You will have to check for crawlers (there may be several generations and they are salmon colored) before you can spray. Wrap some of the branches with double sided sticky tape to monitor for crawlers in May. When you see the crawlers spray with a summer rate of horticultural oil. Follow all label directions. Do not spray when temperatures are in the high eighties in hot weather. Monitor the shrubs for symptoms.