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Boxwood Crown Rot #876556

Asked July 09, 2024, 5:57 PM EDT

I have a whole hedge of fifteen year old boxwood that has developed what looks like phytophtora root and crown rot in spots. Ripping it out isn't an option. Is there any topical or systemic treatment I can try? I have heard that treatment with Subdue (metalaxyl) or similar fungicide can help. Can you advise?

Washington County Oregon

Expert Response

Hi Craig and thanks for your question about treatment for your boxwood with phytophthora root rot. I'll send you the site with information, but most of the chemicals need to be applied by a certified sprayer and they don't tend to eliminate the disease, just set it back. The only chemical you can buy for home use is:

Monterey Garden Phos at 2 to 4 teaspoons/gal water as a foliar spray. Also labeled for soil drench, see label for details. Can be used in landscape sites. Group P7 fungicide.

As you can see from the following article, it is not a cure.

https://pnwhandbooks.org/plantdisease/host-disease/boxwood-buxus-spp-phytophthora-root-crown-rot

Sorry it's not better news and have you had a second opinion on what the disease is? Many of the boxwood diseases look similar at first.
Rhonda Frick-Wright Replied July 09, 2024, 10:49 PM EDT
I brought in a few browned branches and diagnosis was made at Portland Nursery. Here a couple of photos. Can you confirm from the photos that it is indeed phytophthora?

Thanks,

Craig Siegel

Craig Siegel
503.358.7560
<personal data hidden>


On Tuesday, July 9, 2024 at 07:49:21 PM PDT, Ask Extension <<personal data hidden>> wrote:


The Question Asker Replied July 10, 2024, 11:40 PM EDT
Hi Craig- It sure looks like it. So sorry!
Rhonda Frick-Wright Replied July 11, 2024, 12:26 AM EDT

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