Struggling Otto Luyken Laurels

Question: Hi.  Our Otto Luyken Laurels are clearly not doing well.  They were struggling all last year & I hope this year we would have a new start but the leaves are still turning yellow/brown & dropping off.  There is hardly any new leaves but maybe there is some hope with the new blooms......
All last year I treated them with Neem Oil to try to control the scales.  We even tried using Monterey Garden Phos after researching online.  There is currently the scales on 2 of these 4 bushes.  I have one other Otto Luyken Laurel, planted at the same time (6/2020), in an adjacent bed that is so healthy and 4 times the size.  I really want to restore their health and beauty - please help!  Many thanks!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied April 19, 2023, 2:23 PM EDT
response: As you noted, the plants have a population of scale stressing them; in particular, White Prunicola Scale. Scale insects can be very challenging to control and it may take more than a year or two for a high population to be reduced to inconsequential numbers. Scale insects are best controlled by targeting their crawler stage, as described in the linked page (plus its links to general scale information and management). For this particular scale species, those crawler stages appear three times per year as listed in the page above, and while very temperature-dependent overall, generally don't appear until May. Depending on the spray used, it will have little impact if used too early. Dormant oil, a slightly more concentrated version of standard horticultural oil, might kill some of the overwintering generation, but we're too warm now to use this option.  The Garden Phos product you mentioned is not an insecticide and would not be expected to have an impact on the scale, if that was your intent in using it. It might, depending on what the label dictates, limit the spread of a common disease called Cherry Shot Hole, but usually a fungicide is either not needed for this ailment or is not very effective. Keeping the leaves from staying wet due to irrigation that wets foliage is one of the simpler ways to discourage its spread. You can't do anything about rain or dew wetting leaves of course, but shrubs that are not pruned or sheared so heavily that their foliage becomes very dense should have minimal levels of infection that can vary a bit from year to year based on weather. (Wet leaf surfaces can be more vulnerable to infection by fungal or bacterial spores. Good air circulation among the leaves and branches speeds drying time.) The degree of shot hole visible in the photos appears to be very minor, fortunately, so isn't too concerning and doesn't warrant treatment, especially since fungicides might risk harm to other organisms.  Similarly, there is a very minor amount of winterburn on some leaves, a common phenomenon during some winters which causes leaf tips or parts of leaves to discolor or turn dry and brittle. The multiple instances of mild spells this past winter followed closely by a plummet in temperatures to around freezing caused winterburn damage on a variety of evergreens this year. Cherrylaurel, holly, camellia, boxwood, and southern magnolia are common victims of this, but while temporarily an eyesore, it doesn't usually harm the plants and damaged leaves are shed and replaced.  Some leaf yellowing on older growth or the shrub's interior (or lower limbs) is normal for evergreens in spring. This is typical leaf shed that occurs each year, around the time of new growth emerging, though it might be exacerbated for plants under stress with more leaves yellowing then usual. By itself, you shouldn't need to do anything about this, and we would not recommend fertilizing while the scale are still present. (Shrubs rarely need fertilization anyway.)  For now, aside from trying to time pesticide applications (whether horticultural oil or otherwise) to crawler appearance, just monitor the plants for watering needs since we've lately been quite dry. Periodically feel the soil around six inches deep and water well only if it's becoming relatively dry to the touch at that depth. Cherrylaurel are sensitive to being over-watered in soggy soil or with poor drainage, but while tolerant of drought they do best (and are better able to tolerate pests) if not stressed by dry conditions for too long.  If you wish to have help determining exactly when to treat for crawlers, or want to try a systemic insecticide or another type of product that prevents young scale from maturing, seek the services of a certified pesticide applicator as they should have more training/experience in monitoring pests for the best timing of control products. (On some occasions they are the only ones legally able to obtain and apply certain systemic pesticides in Maryland landscapes.) Such individuals can be found at some landscaping companies, arborists or tree-care companies, or occasionally as independent consultants or landscape maintenance managers. We don't maintain such a list but the MD Dept. of Ag. (who authorizes these applicators) does have a search tool on their site, though it's admittedly not super user-friendly.  Miri

responder: The Question Asker Replied April 19, 2023, 2:51 PM EDT
response: Hi Miri, I cannot thank you enough for a very thorough analysis of what is going on with these laurels......from the scale, the shot hole (we've had that issue too), winterburn & watering requirements.  Your incredibly thoughtful explanation of many of these conditions, how and when they occur and how to address it is extremely helpful.  This is a wealth of information - I've read it over a couple of times & gain more knowledge each time!  So much guidance will be incredibly useful & I truly appreciate all the assistance you have provided!  This was an amazing response!!Again, many, many thanks!JulieOn Wed, Apr 19, 2023 at 2:23 PM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied April 19, 2023, 3:01 PM EDT
response: You're very welcome! We forgot to mention that if the scale management is too daunting or seems to be too expensive, it might be simpler and cheaper (and faster) to just replace the infested plants).  Miri