I wanted to dedicate this installment to Boxwood Blight, since this is a disease which has the potential to disrupt formal landscapes all across the state. The disease is fungal, and affects boxwood, especially the cultivated varieties ‘American’ and ‘Suffruticosa’. It is relatively recent in the United States, and was found in Ohio nurseries in 2011. The Ohio State University has been expecting this disease to crop up in residential landscapes, and now is beginning to see this happen. The disease is a new one for me, and I have not personally found it in any of my landscape inspections. To date, Russell Tree Experts has not applied any fungicide preventively for this issue, but we will have a plan in place for the 2019 season. My main goal in writing this article is to begin to raise awareness about this serious disease, and that it is out there.
Boxwood is a plant that many would consider to be overused in landscape design, but perhaps this is because few plants offer the characteristics that Boxwood does. It is evergreen, takes shearing well, and comes in many sizes and forms. Therefore this plant is an exceptional choice for hedges, both formal and informal, for screening or for outlining borders in a garden or landscape. The difficulty with hedges, or with mass plantings of any size, is that the loss of one plant is much more significant than in an informal grouping of trees or plants of varying species where the loss of 1-2 single plants goes unnoticed.
Years ago I helped take care of the landscape at a large private residence that had many formal plantings incorporated into its design, along with less formal groupings of trees. My stress levels were much higher when one of the formal tree arrangements was threatened by the loss of a single tree. Imagine a formal circle of mature shade trees missing one of its members due to disease or storm damage. The effect is similar to missing one tooth out of an otherwise healthy smile. Somehow the overall result of a missing tooth is not helped by the fact that there are 31 other teeth still remaining. And replacing a mature tree to fill in the gap is arguably much more difficult than replacing a missing tooth.
This is the effect Boxwood Blight could have on many, many landscapes we serve. I imagine that 8 out of 10 readers have at least one row of boxwoods somewhere in their landscape. Some of you have massive formal plantings of hundreds of boxwoods. What makes this disease different than others that have been affecting boxwood for years?
In September of this year I attended the 2018 Urban Landscape Pest Management Workshop at The Ohio State University. There, Dr. Francesca Peduto Hand introduced me to this disease with several main points that raised concern:
The disease can infect otherwise healthy plants.
When climate conditions are favorable, the disease can progress very quickly.
Infected plants must be removed and destroyed, and it is not recommended that boxwood be replanted for 3-5 years from the time the last infected plant was removed.
This is like saying you have to pull the infected tooth, and you can’t get a new tooth implanted for 3-5 years. The best defense is knowing what the symptoms are:
First there are dark spots on leaf surface and white sporulation (fungal spores) on the underside of the leaf.
These spots spread on the leaf, eventually causing defoliation.
Black, elongated cankers are evident on defoliated stems.
Unfortunately, once symptoms are found, the plant must be destroyed. The best preventive measure is to make sure any new plants coming into the landscape from the nursery are carefully inspected and approved as symptom free.
Another preventive defense is a regimen of fungicide applications. These can be costly depending on the size of the hedge and the frequency of applications. Also consider that since the applications are preventive, they need to be repeated on a seasonal basis and would have to become part of a permanent landscape budget.
A pdf with good photos and symptom descriptions authored by the Connecticut Agricultural Experiment Station can be found here:
I leave you, dear reader, with the heartfelt wish that your landscape may remain disease free! May you draw nothing but pleasure and peace from the plants which surround you. Be wary of what may be hitching a ride into your landscape on new plants.
Your friendly neighborhood arborist,
José Fernández | Regional Manager, Russell Tree Experts
José became an ISA Certified Arborist® in 2004, and a Board-Certified Master Arborist® in 2015. Currently he is enrolled at The Ohio State University pursuing a Master’s Degree in Plant Health Management. José likes working around trees because he is still filled with wonder every time he walks in the woods. José has worked at Russell Tree Experts since 2012.