Japanese Hollies not doing well - Ask Extension
Good morning! We have four Steed's Upright Japanese Hollies, planted in 2017, which have been thriving until this summer. Now one of them is showing...
Knowledgebase
Japanese Hollies not doing well #716854
Asked August 24, 2020, 9:47 AM EDT
Good morning! We have four Steed's Upright Japanese Hollies, planted in 2017, which have been thriving until this summer. Now one of them is showing the problems identified in the photos below, and the problem is spreading to its neighbor. They are all planted in fairly well-drained soil, in full sun, and as I said, have been thriving since they were planted. What do you think is wrong with them, and is there anything I can do? Any help would be greatly appreciated.
Glenn Kensington, MD
Montgomery County Maryland
Expert Response
Hi - Unfortunately, we see what appear to be scale insects on the branches of your holly. Scales are small insects with sucking mouthparts which they insert into the branches to feed on the sugary sap. When soft scales are present on a shrub, you may detect honeydew (a sticky residue that results from their feeding) as well as sooty mold, a black fungus that grows on the honeydew. If left unmanaged, a scale infestation can lead to yellowing foliage and eventual branch dieback and overall decline of the plant. Here is our information about scale insects.
https://extension.umd.edu/hgic/topics/soft-scales-trees-and-shrubs
https://extension.umd.edu/hgic/topics/armored-hard-scale-trees-and-shrubs
We would need to see very close and clear photos of the scales (the raised bumps on the branches) in order to determine exactly what type they are.
Scale infestations in general can be very difficult to manage on landscape plants. Since you have four of these hollies, our recommendation would be to remove this worst one altogether in an effort to limit the scale from moving to the other plants. Treat the other hollies with a dormant rate of horticultural oil in the dormant season (after leaves have fallen from deciduous trees).
In addition, Japanese hollies are very susceptible to black root rot which be an issue in heavy soils with poor drainage. If you have a sprinkler system or water on a schedule this can affect the root system of the plants too. Check the drainage in the area and correct if possible. Keep mulch no thicker than two inches in depth and away from the base of the stems. Prune out any dead plant material. This disease doesn't kill quickly. It affects branches here and there. It can take years to either overcome the plant or get to a point of losing their attractive form. No chemical control is recommended.
Christa
https://extension.umd.edu/hgic/topics/soft-scales-trees-and-shrubs
https://extension.umd.edu/hgic/topics/armored-hard-scale-trees-and-shrubs
We would need to see very close and clear photos of the scales (the raised bumps on the branches) in order to determine exactly what type they are.
Scale infestations in general can be very difficult to manage on landscape plants. Since you have four of these hollies, our recommendation would be to remove this worst one altogether in an effort to limit the scale from moving to the other plants. Treat the other hollies with a dormant rate of horticultural oil in the dormant season (after leaves have fallen from deciduous trees).
In addition, Japanese hollies are very susceptible to black root rot which be an issue in heavy soils with poor drainage. If you have a sprinkler system or water on a schedule this can affect the root system of the plants too. Check the drainage in the area and correct if possible. Keep mulch no thicker than two inches in depth and away from the base of the stems. Prune out any dead plant material. This disease doesn't kill quickly. It affects branches here and there. It can take years to either overcome the plant or get to a point of losing their attractive form. No chemical control is recommended.
Christa
Hi Christa:
Thank you so much for your quick reply. I've tried to get clearer photos of the plant. We've had scale insects on other hollies in years past, so I have some familiarity with the problem. But on this plant I'm not seeing the honeydew or the sooty mold. Anyway, I'm sending somewhat clearer photos in the hope that they help you identify the type of scale - I've included one to show the leaves and two of the same branch against different backgrounds/lighting.
Best for now!
Thank you so much for your quick reply. I've tried to get clearer photos of the plant. We've had scale insects on other hollies in years past, so I have some familiarity with the problem. But on this plant I'm not seeing the honeydew or the sooty mold. Anyway, I'm sending somewhat clearer photos in the hope that they help you identify the type of scale - I've included one to show the leaves and two of the same branch against different backgrounds/lighting.
Best for now!
Thank you for the photos. We do not clearly see live scale in these pictures, but have attached an edited version of your prior photo where we think we have seen some scale on stems closer to green(ish) leaves. (We circled the suspected scale.)
The black residue on many stems in the first original photo is what appears to be sooty mold, as Japanese Holly do not normally have this dark stem coloration; the blotchy nature of its distribution also suggests sooty mold. It's more noticeable on the younger green stems than the older stems with browner bark.
Miri
The black residue on many stems in the first original photo is what appears to be sooty mold, as Japanese Holly do not normally have this dark stem coloration; the blotchy nature of its distribution also suggests sooty mold. It's more noticeable on the younger green stems than the older stems with browner bark.
Miri
Thank you so much for that detail. Very clear now.
We'll follow the treatment your colleague recommended!
We'll follow the treatment your colleague recommended!
You're welcome!
