Holly Shrubbery Dieback

Question: I have a row of eight holly shrubs in front of the house next to the street.  Last year two began to experience die back (withering leaves, leaves covered with a black substance, stems dying). I sprayed them with a 3-in-1 product to fight disease and insects.  This year a third Holly is experiencing the same problem, and the original two have not fully recovered.  

1. Is there anything I can do to save these plants?
2. How to I prevent the spread of these problems to the other shrubs?

responder: An Ask Extension Expert Replied August 07, 2024, 8:27 AM EDT
response: Hi John, Thank you for your question and pictures of your holly shrubs. After some research it may be that your holly has phytophthora root rot, a water mold fungi. Usually yellowing of the leaves, early leaf drop, slowed plant growth, and twig dieback are seen at early stages of the disease. Your pictures, especially the second one, appear to match this description. As the disease progresses limbs dieback to the main trunk and you may notice a black streak from the limb back towards the roots.  Some of the conditions that allow this fungi to flourish include planting in a poorly draining or wet spot, too deep planting depth, or over-mulching of the plants. This summer, with its heat, drought and now recent heavy rains, is probably further stressing your holly.  Actions you can take to prevent disease spread to the remaining shrubs include making sure they weren't planted too deeply to start. Attached is a good image of correct planting and correct mulching where the mulch is not packing up to the base of the shrub.  Treating with fungicides is successful as a preventative measure so unfortunately the two hollies that have a lot of die back are not likely to grow back. After removal, it is recommended to fumigate and aerate the soil before placing another woody shrub in its place. I have also attached links to other extension articles describing typical diseases affecting holly for your information. I'm sorry I don't have better news for you but hope this helps you save the other Hollys in your yard. Cyndy Moyer DC Master Gardeners   https://hgic.clemson.edu/factsheet/holly-diseases-insect-pests/  https://extension.psu.edu/holly-diseases

responder: The Question Asker Replied August 07, 2024, 5:12 PM EDT
response: Thank you Cyndy Moyer for the thorough, specific and speedy response to my inquiry.  I’m proceeding as suggested and have ordered a fungicide to apply to the soil.  Hoping for the best outcome to be saving the remaining Hollies.  Regards, John BowmanSent from my iPad On Aug 7, 2024, at 8:27 AM, Ask Extension <<personal data hidden>> wrote:   ﻿

responder: An Ask Extension Expert Replied August 08, 2024, 9:47 PM EDT
response: Thanks for the update on your hollies! Following up on my colleague’s recommendation, while certain fungicides may act as preventatives, unfortunately, generally fail as curatives. Also, applying fungicides can adversely affect the beneficial fungi your plants need to thrive. Phytophthora are oomycetes, "fungus-like” organisms, that can already be present in the soil, or can be introduced by infected container plants, and can persist in the soil for many years. Hence, “Chemical management of these diseases usually is impractical or not economical in land-scapes.” The good news is that there are gardening methods to control the conditions that favor P. and many plants with resistance to Phytophthora! 1. Remove affected plants. 2. Replace with resistant plants. Winterberry, Yaupon, Buford & some Chinese hollies, roses, & Spicebush are some examples. For a full list, see below. 3. Avoid over fertilizing; only apply if a soil test indicates a deficiency. 4. If needed, remedy any drainage issues, such as drain-aways filled with arborist woodchips, raised beds, planting in berms, regrading, etc. 5. Enjoy your garden! Thank you so much and please keep us posted! Kate McLynn, DC Master Gardener Resources: https://static1.squarespace.com/static/50db5688e4b00220dc71db15/t/5176d8efe4b0c6cbe9570392/<personal data hidden>73/Info+Sheet_Phytophthora+Resistant+Plants.pdf As an example, Yaupon Holly’s native ranges north to Virginia, but as our summers warm, can be a good “near-native” for DC. Highly resistant with red fruit (females), evergreen, but leaves lack prickles, easily pruned & compact cultivars are available.https://www.pubs.ext.vt.edu/2901/2901-1079/2901-1079.html#:~:text='Nana'%20yaupon%20holly%20is%20a,20%20feet%20with%20beautiful%20fruit.

responder: An Ask Extension Expert Replied August 08, 2024, 9:48 PM EDT
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responder: An Ask Extension Expert Replied August 09, 2024, 8:20 AM EDT
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responder: The Question Asker Replied August 17, 2024, 9:23 AM EDT
response: Kate -Thank you for the follow up to the first response I received regarding problems with my Holly shrubs.  And I especially appreciate the list of possible replacements.   Sorry it took so long to respond but please know your message was/is much appreciated. John BowmanSent from my iPad On Aug 8, 2024, at 9:47 PM, Ask Extension wrote:﻿

responder: The Question Asker Replied September 12, 2024, 12:18 PM EDT
response: Kate -You asked to be updated on my Holly dieback so I’m responding.  I had Bartlett Trees examine the plants.  The arborists (Forest Bowen) took soil samples and sent them for evaluation.  The results are listed below; basically the analysis did not find root rot fungi.  For now only three of the plants have been severely damaged.  If they don’t appear to be recovering  I may try replacing them with something from your list of suggestions. Regards,John BowmanSeptember 11, 2024 Client Information: Name: John Bowman Sample Information: Plant Name: Dragon Lady Holly (Ilex x aquipernyi)   Diagnosis Information: William Parrott has diagnosed your sample as follows:  Diagnosis: The submitted root sample was also tested for Berkeleyomyces basicola, the causal agent of black root rot disease, using a baiting procedure. This fungal pathogen WAS NOT detected from the root tissue.  ******************************** September 5, 2024 Client Information: Name: John Bowman Sample Information: Plant Name: Dragon Lady Holly (Ilex x aquipernyi)   Diagnosis Information: Mason Federmeyer has diagnosed your sample as follows:  Diagnosis: Phytophthora root rot WAS NOT detected from the root sample using an Enzyme-Linked Immunosorbent Assay (ELISA). On Aug 8, 2024, at 9:47 PM, Ask Extension wrote:

responder: An Ask Extension Expert Replied September 12, 2024, 5:34 PM EDT
response: Dear John, Thank you so very much for getting back with us with the good news on the pathogen tests provided by Bartlett!  Did Barlett have any insights on what was causing the dieback?  According to NC State Extension, https://plants.ces.ncsu.edu/plants/ilex-x-aquipernyi/ , Lady Dragon Hollies benefit from some shade in hot summers.  Could the dieback possibly be related to our very hot summer this year and low rainfall?  Hope the hollies rebound! Hope you will keep us posted on their progress. Many thanks, DC Master Gardeners Kate

responder: The Question Asker Replied October 03, 2024, 9:36 PM EDT
response: Kate -Just a quick follow up.  There are mushrooms growing near the plants in question but I’m assuming that’s a different kind of fungus and likely due to the rain.  Also, the Hollies are showing new growth near the base.  Still not sure if I should replace them but there doesn’t seem to be any further dieback.  Just thought I would share this.Regards,John BowmanOn Sep 12, 2024, at 5:35 PM, Ask Extension wrote:﻿

responder: An Ask Extension Expert Replied October 03, 2024, 11:01 PM EDT
response: This is the best news ever! Mushrooms can be a good indicator and hope  your hollies make a full recovery!If the new growth is still very young and tender when our temps drop & winds increase, might be worth considering giving them some wind protection.  Thank you for keeping us posted!