3 Landscape Problems - Ask Extension
Hope you are all keeping well. Some of our plantings are not so well.
1) Blackish film (mold?) on leaves of holly tree. What to do?
2) We have 3 Otto ...
Knowledgebase
3 Landscape Problems #617595
Asked March 18, 2020, 3:04 PM EDT
Hope you are all keeping well. Some of our plantings are not so well.
1) Blackish film (mold?) on leaves of holly tree. What to do?
2) We have 3 Otto Luykens cherry laurels planted in partial shade that screen AC compressor unit. We have been seeing some die-back for several years, one completely died at year end. Should we replace one or all with same or alternative specimens?
3) We have skimmia planted in shady area since 2009 that suffered heavy die-back last year. Should we replace some or all with same or alternative specimens?
Thank you,
Myron Rosen
Anne Arundel County Maryland
Expert Response
The black film on your holly leaves suggests that there was a problem last year with a sucking insect- most likely cottony camellia scale. Sucking insects excrete honeydew, which fall on the leaves below, and then what is called 'sooty mold' grows on it, which is the black film you see.
Here is more information about this pest: https://extension.umd.edu/hgic/topics/cottony-camellia-scale-shrubs
If the infestation is heavy and the tree is large you may need the help of a professional to reach the problem, but in that case be sure to use what we suggest for treatment so to preserve beneficial insects.
Cherry laurels can have multiple problems, including white prunicola scale, but they also can't stand too much water. As a broadleaf evergreen they also are subject to leaf dessication (drying out) that comes with winterburn or being constantly blown on by your ac unit.
Check for the prunicola scale- compare to #4 here: https://extension.umd.edu/hgic/topics/armored-hard-scale-trees-and-shrubs
You can read a recent blog post of ours related to problems of Cherry Laurel here:
https://marylandgrows.umd.edu/?s=laurel
For skimmia, they are not easy to grow and they will hate too much water. Given the historic levels of rain we got last year, that could be indicated.
If you plan to replace these plants, we would go with other species, for instance, perhaps ornamental grasses near (but not too close) your ac unit.
Christine
Here is more information about this pest: https://extension.umd.edu/hgic/topics/cottony-camellia-scale-shrubs
If the infestation is heavy and the tree is large you may need the help of a professional to reach the problem, but in that case be sure to use what we suggest for treatment so to preserve beneficial insects.
Cherry laurels can have multiple problems, including white prunicola scale, but they also can't stand too much water. As a broadleaf evergreen they also are subject to leaf dessication (drying out) that comes with winterburn or being constantly blown on by your ac unit.
Check for the prunicola scale- compare to #4 here: https://extension.umd.edu/hgic/topics/armored-hard-scale-trees-and-shrubs
You can read a recent blog post of ours related to problems of Cherry Laurel here:
https://marylandgrows.umd.edu/?s=laurel
For skimmia, they are not easy to grow and they will hate too much water. Given the historic levels of rain we got last year, that could be indicated.
If you plan to replace these plants, we would go with other species, for instance, perhaps ornamental grasses near (but not too close) your ac unit.
Christine
