Hibiscus – Rose of Sharon disease? #637147 - Ask Extension

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Hibiscus – Rose of Sharon disease? #637147

Asked May 18, 2020, 9:24 AM EDT

Hello. Can you tell what this white stuff is on our Hibiscus – Rose of Sharon? Do you know what we need to do? Please see attached pictures. Thanks,

Anne Arundel County Maryland

Expert Response

Hello Kevin,

This appears to be scale - a sap-sucking insect. These are not in focus, but they resemble Cottony Camellia Scale which are starting to lay eggs. https://extension.umd.edu/hgic/topics/cottony-camellia-scale-shrubs

Rose-of-Sharon are resilient shrubs and should recover well once the scale are controlled. Pruning of the most infested stems (even if it is the majority of them) should be fine; new growth will emerge to replace it. Otherwise, spraying existing surfaces as well as later new growth (if you opt to prune) will help smother the vulnerable crawlers (hatchlings) when they emerge in June. Thorough coverage of all surfaces of the plant (including underneath leaves) is important for effective treatment; horticultural oil or insecticidal soap should work while avoiding impacting beneficial insects that will arrive to prey on the scale. Several sprays a week or so apart (check the label) may be needed.

Because this population is so extensive, and this scale feeds on many kinds of shrubs, check your garden for other infestations and treat them with the same sprays. (Not all plants can or should be pruned back, however.)

Miri
Thanks Miri.  I attached another picture.  Hopefully it is clearer.  The stuff is all over most of the leaves and the branches.  It looks like it may be on the ground underneath the plant also.


The Question Asker Replied May 18, 2020, 5:04 PM EDT
Our answer remains the same, other than we can't tell how large your plant is.
You could either prune out the worst infested branches, or even put on gloves and just hand-squish/ remove as many as you can.

There is more information at link in our reply above.


Christine
ok Thanks.
The Question Asker Replied May 19, 2020, 11:02 AM EDT
You are welcome.

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