possible boxwood pest?

Question: Removing old mulch around boxwoods I found what appeared to be white roots, but very fine and thread-like with small, white nodules--some with only a couple, some with many. Some online research pointed to the possibility they were southern root knot nematodes, but images varied so much, I could not be certain. If not, can you tell what they are? Photos are attached. Whatever they are, what is my best course of action?

Thank you in advance...and for your past help too!

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 March 08, 2023, 12:50 PM EST
response: We typically don't see root nematode infestations on boxwood, but it might be possible. For some reason we can't open your photo files (they look the right format and size, so some tech just isn't cooperating)...would you mind re-sending?  Have the boxwoods exhibited any notable symptoms that makes you suspect they are ailing? As for the visible swellings in the root zone, might there have been plantings there last year that were either annuals or possibly weeds (Lesser Celandine comes to mind for its root bulblets) that left behind that type of root structure?  Out of curiosity, was the old mulch being removed for a particular purpose? (Planting something new, checking on boxwood roots...?) We ask because typically when new mulch is needed, the old layer is kept in place so it keeps decaying into beneficial organic matter for the soil, and a new layer is put on top to supplement whatever amount is needed to bring it back up to "full" depth. (Two to three inches in total depth is sufficient or plenty for most situations.)  Fine white threads by themselves may be mycorrhizal fungi, which are beneficial fungi that attach to plant roots and provide them with a boost in moisture and nutrient absorption. Or it's a fungus harmless to the live plant but which is decaying the mulch, which would be a good thing since that's what we want to encourage. We'll take a look at the images if they come through on the second try and will see if our plant pathologist things nematodes are responsible.  Miri

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 March 08, 2023, 12:51 PM EST
response: Adding: if file attachments aren't cooperating, you could try pasting the images into the body of the message itself. We routinely receive them both ways and sometimes can enlarge images when they're incorporated into the reply.

responder: The Question Asker Replied March 08, 2023, 4:36 PM EST
response: Thanks for your reply. Screenshots of the photos are below. I have been told by a couple of landscapers that old mulch (this is shredded hardwood) should be removed before new mulch is put on. It has rather formed a “helmet” over the soil. I am also in the process of adding to and amending soil in several beds where soil has eroded, including the bed where I found these—whatever they are. These boxwoods have been in the same bed, by themselves, for many years. It’s a small bed where we started with four small boxwoods about 15 years ago. As they grew, two were moved elsewhere and two have remained for probably 10 years. We have had minor, treatable problems over the years (no blight, thankfully). Leafminers and mites are all I can think of. These two are not showing signs of distress other than some discoloration from previous leafminer damage. I have not checked around any of my other boxwoods. Two that are less protected are showing some stress, but I think it is from frost/freeze.     I came to search on Southern root-knot nematodes after reading about them while searching for boxwood pests matching the description of my find because several sites mentioned these nematodes Including the quote below from Clemson. But perhaps they are more common farther south:    “Boxwoods are susceptible to several parasitic nematodes (microscopic round worms), including the Southern root-knot nematode (Meloidogyne incognita), the ring nematode (Mesocriconema), the lesion nematode (Pratylenchus), and the stunt nematode (Tylenchorhynchus).”    When you’ve seen the photos, let me know what you think, and thanks again for providing this service!

responder: Answered by theHome 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 March 09, 2023, 10:41 AM EST
response: Removal of mulch each year isn't necessary. As long as it is an organic mulch (shredded hardwood or nuggets, not rubber, and preferably not dyed) it will break down in place and enrich the soil. It can be gently 'fluffed" to break it up and perhaps look better, but work around Boxwood should always be careful as they are shallow-rooted.  As far as what you have there, it looks like it could be nematodes though they are unusual here and our long-time plant pathologist has not seen them on Boxwood before. Are there any plants growing beneath and around your boxwood? It's worth mentioning that there are some plants, like Liriope that have roots that can look like that.  To get a good i.d., we'd suggest taking a sample to your local Montgomery County Extension office: https://agnr.umd.edu/about/directory/montgomery-county Contact Steve Dubik at the link above and he can walk you through how to submit the sample so that he can send it to the University of Maryland lab for testing.  Good luck.   Christine

responder: The Question Asker Replied March 09, 2023, 1:56 PM EST
response: Thanks, Christine, There are no other plants in the bed and only a thin strip of grass at the edge of the bed that then meets a flagstone walk. The bed continues around the corner of a carport shed where there are mature hostas and a less-than-healthy mountain laurel. Only one hosta is close to one of the boxwoods, but the bulk of the findings were at the other end of the bed around the other boxwood.     Thanks for the mulch tips as well. The rationale I had heard for removal was that pests and dieases can lay dormant over the winter and reinfect plants in the spring, especially when a lot of leaf drop occurs on the mulch. We have, for example, had some really bad lacebugs on our numerous azaleas, and some scale issues have developed on various shrubs, incuding laurels, euonymous, and Japanese hollies.     I appreciate your help and will consider having a sample analyzed.     Best, Ruth

responder: Answered by theHome 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 March 10, 2023, 10:31 AM EST
response: Hello again. I should have mentioned that there is no cost associated with submitting a sample to the Derwood Extension office. Given how rarely this pest has been seen in our area it would be of interest to know for sure if that is indeed what that is. Thank you for considering.   Christine