Identify white powdery substance on stocks of shrubs dead leaves and holes in leaves

Asked April 5, 2020, 12:44 PM EDT

Need help to identify white powdery substance on stocks of shrubs dead leaves and holes in leaves. It is only affecting one shrub species in our landscape.

Howard County Maryland

1 Response

Left photo - The white stuff on the branches is an insect called white prunicola scales. They feed on the plant sap and they are a very common problem on cherry laurels. We see infestations like this a lot.
Read through our webpage to understand the life cycle, https://extension.umd.edu/hgic/topics/armored-hard-scale-trees-and-shrubs

In winter, apply a dormant horticultural oil spray you have a light infestation (too late to do this now.)
For a moderate infestation, use insecticidal oil or soap sprays on crawlers (the juveniles) in May, June, mid-July to mid-August, and again in September. (There are 3 generations a year, so they will keep hatching into crawlers.)
If the infestation is not heavy, use a soft brush to brush away the white scale covers from the branches. During the growing season, wrap a piece of double-sided tape around one of the branches. This is a test to monitor the active crawler (juvenile) stage of these insects. They are more susceptible when they come out in May/June depending upon temperature and there may be several generations per year. When you see crawlers sticking to the tape, that is a good time to apply horticultural or insecticidal soap according to label directions.
Avoid highly toxic insecticides in order to preserve the beneficial insects which will help you keep this pest under control.

See our blog on this insect pest. https://marylandgrows.umd.edu/2019/09/25/qa-what-is-this-white-growth-on-my-cherry-laurel-shrub/

Middle photo - Holes in leaves - This is called cherry shothole, a fungal disease favored by wet wether. The damage is cosmetic and no chemical controls are recommended. Rake up any fallen foliage. The plant will recover.

Right photo - We notice a downspout in the photo. Make sure it is not dumping water in the root zones of the plants. If so, divert it. Keep the plants as healthy as possible. Take a look at our blog on cherry laurel and how to establish them in your landscape.
https://marylandgrows.umd.edu/2019/01/07/qa-whats-wrong-with-my-cherry-laurel-shrubs/

Marian