From: Ask Extension <<personal data hidden>>
Date: May 6, 2024 at 10:24:10 PM PDT
To: Lynne Winkler <<personal data hidden>>
Subject: Thank you for your Ask Extension question (#0137281)



Dear Lynne,

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YOUR QUESTION #0137281:

Laurel hedge disease

Hello, I have a 30+ year old laurel hedge that appears to be dying. Can you tell me what is sassing this and if there is anything I can do to save it? Thank you.

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Wow, your hedge does have troubles. Diagnostic work remotely is a challenge. I recommend you hire a certified arborist if we can’t figure this out together.
To try this, I need a closer photo of a branch showing the place where it goes from alive to dead, if possible. A couple of distant views also. You need to illustrate the whole thing so we can see any pattern to the dead spots.
How far back does the fully dead area reach? Dead is brittle and no green if you scratch the bark. Are these limbs dead clear to the trunk? Do you see lesions on the trunk bark?
Then also, tell me everything you can think of about it. When did this start and how fast is it changing? What fertilizer or herbicides have been used in the area, and when. Describe summer irrigation. Has any construction or ditching been done?
I hope we can get this, but it does become sort of a game of 20 questions.



The bark looks odd on the dead parts. Can you get a really close photo of it tomorrow? What do backs of leaves look like on the "sick but not dead" leaves? It almost looks like a scale insect. What happens if you scrape off the "bumps" on the bark? (Internet search "scale insect" and select images for a survey of how the different ones appear.)
Another idea is that your plant is burned by something like hot exhaust from a car, truck, or maybe a gas powered hedge trimmer tool?





The same photos loaded multiple times, as this web forum has challenges. As I look carefully this morning, I think your shrubs have a cottony bark scale infestation. I’ll share a zoomed in portion of your photo. Compare it to images on this Azalea bark scale information page from OSU. The name is “Azalea”, but they can live on other plants as well. Am I right? Scrape them off and look close.
What to do? I’ll list resources for you because there are more steps than I can write up on this forum. Especially chemical control needs to be carefully timed and follow insecticide labels exactly.
For right now, get the heavily infected dead and dying parts removed and off of your property rather than composting onsite. Do this right away because it’s time for eggs to hatch and the crawling stage to spread into new parts of your shrubs.
The pages I’m sharing give instructions about applying sticky tape to catch crawlers. I don’t think you’ll trap all of them, but it is a good way to monitor when the critters are there. A 10x magnifier can help you see them. I’ve used the magnifier app on my phone sometimes.
The “biological control” listed is other insects eating these, so don’t rush out with broad spectrum insecticide. Instead, follow the cultural controls listed first. Prune, scrape, water correctly but don’t fertilize.
Don’t be dismayed and give up on the plants yet. English laurel can regrow even if you nearly cut it to the ground, which is called “rejuvenation pruning”. My mother’s Camellia shrub was covered with scale a few years ago. We pruned off what we could and watered it better to keep it strong. The scale is gone and the plant shape filled back in. Perhaps the plant defenses took over, or predatory insects cleaned it up. If you decide pesticides are necessary but you are unable to apply them correctly yourself, consider hiring a certified arborist company with licensing to do it for you.
Okay, here’s those information pages to read before you actually do anything.
PNW Handbook Azalea Bark Scale page.
Landscape plants scale insects page of the PNW Handbook. Note the different control options.
The PNW Handbook page for chemical control of landscape pests.
(Oh, and I’m attaching the zoomed in version of your photo.)

This is great information and I will get busy on the steps you suggest. Crossing my fingers that we can save our beautiful old hedge!



The advice I read is to cut out the heavily infected parts. And use brush to clean parts you leave. That’s a chore, so cutting is the easier choice.
Exactly where you prune to is a bit of an art. Generally take a branch back the it’s base, so the don’t have lots of little stubs. 
Oh, and sweep up leaves and squirt off pavement when done, since goal is to send insects on their way.