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Boxwood Trouble #877187

Asked July 14, 2024, 6:06 PM EDT

Hello. I’m writing about an issue with a boxwood shrub. I think I have “loved it to death.” Its leaves are paler than my other boxwoods, and there are very large sections of burned out/dead branches. As background, this boxwood was treated with imidacloprid in early April for leaf miners; transplanted in late April; and thinned and sheared in late May. I sprayed it and my other boxwoods with insecticidal soap (and a light dilution of neem once) to combat mites every week to 10 days through early June. In late June my husband sprayed it with a fungicide (Cleary 3336) that he was using on the lawn (and in the lawn concentration, not ornamental plant concentration). It started showing signs of yellowing in mid-June, and really started going downhill in early July. I’m wondering if this boxwood is a goner. I’m kind of hoping it is a burn from the fungicide and heat stress, but am worried about blight spreading to my other boxwoods. I’ve attached some photos. You can see black spots on some of the dead leaves. (FYI, the imidacloprid was applied without my consent, and we don’t normally use a fungicide on the lawn but we had a severe outbreak of anthracnose last year. I try to avoid pesticides other than soap and neem, and potassium bicarbonate or milk for powdery mildew). Thanks!

Montgomery County Maryland

Expert Response

That was a lot of stressors over a short period of time. Even under the best conditions Boxwood can have many issues as noted in our page here: 
https://extension.umd.edu/resource/boxwood-identify-and-manage-common-problems/
We are not sure what is causing the foliage curling/twisting, but so many of the twig tips are dead that we suggest either just starting over, or to cut it back drastically and see if it regrows.
Here is what Boxwood Blight looks like, which tends to drop leaves.: 
https://extension.umd.edu/resource/boxwood-blight/

Be sure to read and follow the management and timing instructions in the link above, the less spraying the better, that will spare beneficial, non-target organisms and keep your landscape healthier overall.

As far as anthracnose on your lawn, how was that diagnosed? It is not usually a problem on home lawns, but on intensely managed golf greens (that are a different type of grass). We wouldn't suggest a general lawn application of fungicides. 


Christine



Thanks so much for the quick response. As much as I love our boxwoods, which were mature when we bought our house 25 years ago, they are just too temperamental. I will pull that one out and replace with a native alternative. We’ve had luck with Inkberry holly gem box (ilex glabra). In fact, we are slowly but steadily removing sections of lawn and beds and replacing with native perennials.

The lawn anthracnose was diagnosed (visually) by the same company that - despite being told not to - treated our boxwoods with imidacloprid. The technician said we had anthracnose and brown patch throughout the lawn. I didn’t question him because our lawn has looked horrible every summer for years, beyond what I would consider heat/drought stress (and I could see signs of fungal disease). We sprayed with a fungicide twice, for the first time ever (the lawn actually does look a lot better this year so far). We’ve stopped spraying the lawn, especially since we’ve worked hard to improve our soil microbiome. Our regular lawn company is Naturalawn with the “Pesticide Free - Natural Alternative” program. They’re not the ones who diagnosed the anthracnose, although one of their technicians did say our lawn had brown patch.

Thanks again for the advice and sorry for the long response!

The Question Asker Replied July 16, 2024, 10:23 AM EDT

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