managing with white prunicola scale - Ask Extension
Please see the attached photos. It appears one of our cherry laurels succumbed to this scale. We'd like to replace it with another cherry laurel. Is t...
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managing with white prunicola scale #595375
Asked September 08, 2019, 4:46 PM EDT
Please see the attached photos. It appears one of our cherry laurels succumbed to this scale. We'd like to replace it with another cherry laurel. Is that fool hardy? If we do that, what precautions should we take? We have an adjacent cherry laurel on which I don't see any white scale. How do we prevent it from an infestation? On the other side is an adjacent tree peony. Is it susceptible to this scale too?
We appreciate your advice.
Howard County Maryland
Expert Response
Hi - These are called white prunicola scales. They are insects that feed on the plant sap and they are a very common problem on cherry laurels. We see infestations like this a lot.
First, read through our webpage to understand the life cycle, which will help you target sprays if that is the course you want to take. 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. 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.) When there are highly concentrated infestations on branches like you have, scrub them off with a stiff brush (not wire) then spray. This knocks off their protective cover (their "scale").
Avoid highly toxic insecticides in order to preserve the beneficial insects which will help you keep this pest under control.
If you don't want to deal with this problem repeatedly, I recommend choosing a different type of shrub.
We did not find any research information indicating that this type of scale would move to tree peonies.
Christa
First, read through our webpage to understand the life cycle, which will help you target sprays if that is the course you want to take. 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. 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.) When there are highly concentrated infestations on branches like you have, scrub them off with a stiff brush (not wire) then spray. This knocks off their protective cover (their "scale").
Avoid highly toxic insecticides in order to preserve the beneficial insects which will help you keep this pest under control.
If you don't want to deal with this problem repeatedly, I recommend choosing a different type of shrub.
We did not find any research information indicating that this type of scale would move to tree peonies.
Christa
Thank you very much for your helpful response. The affected laurel is totally gone. We've decided to replace it this fall with another cherry laurel. Do we need to treat or replace the soil before we replant?
There is some minimal infestation on the adjacent laurel. How soon can/should we apply the dormant oil?
There is some minimal infestation on the adjacent laurel. How soon can/should we apply the dormant oil?
If you replant with another cherry laurel, you do not need to treat or replace the soil. Water the plants up until the ground freezes. Check the moisture weekly.
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/
To treat the shrub with the scale, plants have to be dormant. Wait until other deciduous plants drop their foliage. Follow all label directions.
Marian
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/
To treat the shrub with the scale, plants have to be dormant. Wait until other deciduous plants drop their foliage. Follow all label directions.
Marian
