Phomopsis blight. Photo: Robert L. Anderson, USDA Forest Service, Bugwood.org.
Phomopsis is a fungus that causes shoot blight and twig cankers. The disease is most common among junipers.
Phomopsis may also affect other evergreen ornamentals and a few deciduous trees. This may include American and Oriental arborvitae, hinoki cypress, English yew, Douglas fir, true fir, hemlock, European larch, redwood, white cedar and jack pine.
The fungus first affects foliage, then spreads to and sometimes kills stem tissues. It may eventually kill the plants.
Signs and Symptoms
Look for die-back of the new shoot growth (tip blight). Small yellowish spots appear on young needles within a few days after infection. The new growth changes from light yellow green to reddish brown to ash gray as it dies from this fungal disease.
Phomopsis starts on immature scale leaves or needles. It only kills new growth. Mature needles are resistant. If more than just the new growth is killed, other fungal diseases or environmental injury is involved.
When the fungus invades young stems, it may girdle them if they are less than one third inch in diameter. The portion of the seedling above the girdled area then dies. The resulting diseased plant is an unsightly mix of health green and infected dead reddish brown foliage. Older branches (more than one third inch in diameter) are more resistant to infection, and lesions that form on this size stem usually heal.
Phomopsis blight occurs anytime succulent young foliage is available. Spores from the previous year’s infected twigs cause infections early in the year. These new infections cause subsequent infections throughout the growing season. Infections become more severe with long periods of wet and warm conditions.
Damage from drought may be confused with Phomopsis blight. In both cases, tips of branches may be killed. However, the line between green and dead tissues is sharp in seedlings with Phomopsis blight and gradual in seedlings affected by drought.
What you can do
Susceptibility to Phomopsis blight varies considerably among junipers. Ask for resistant stock at your garden or landscape center or consider planting another type of evergreen.
Avoid planting junipers or other susceptible species in poorly drained areas.
Avoid wounding or injuring when planting or cultivating.
Prune out and burn or bury all blighted plant parts as they appear. The plant’s appearance will suffer greatly. This will reduce the severity of Phomopsis but will not eliminate the disease.
Restrict pruning and shearing to dry weather. Aggressive maintenance pruning will promote the growth of new, susceptible tissue, so wait for mid-summer dry conditions. Sterilize pruning tools between cuts and especially between plants, using rubbing alcohol or a 25 percent solution of chlorine bleach.
Do not use infected branches or needles as mulch.
If overhead sprinkling is used, water early in the day so the seedling dries before nightfall.
Remove a severely infected plant and replace it with one that is more resistant. Some juniper cultivars are less susceptible to the disease. You may also want to consider a different species.
Resistant varieties
The following juniper varieties are generally resistant to Phomopsis blight.
Juniperus chinensis – Chinese Juniper
- ‘Foemina’
- ‘Keteleeri’
- ‘Mint Julep™’
- ‘Mountbatten’
- ‘Pfitzeriana’
- ‘Pfitzeriana Aurea’
- ‘Robusta’
- ‘Robusta Green’
- var. sargentii (Sargent Juniper)
- var. sargentii ‘Glauca’
- ‘Wintergreen’
J. communis – Common Juniper
- ‘Ashfordii’
- ‘Aurea’
- ‘Aurea-spica’
- ‘Depressa’
- ‘Hulkjaerhus’
- ‘Repanda’
J. conferta
- ‘Suecica’
J. horizontalis – Creeping Juniper
- ‘Depressa Aurea’
- ‘Tripartita’
- ‘Wiltoni’ (‘Blue Rug’)
J. sabina – Savin Juniper
- ‘Arcadia’
- ‘Broadmoor’
- ‘Knap Hill’
- ‘Skandia’
J. Scopulorum ‘Silver King’
J. squamata – Singleseed Juniper
- ‘Campbellii’
- ‘Prostrata’
- ‘Pumila’
- var. fargesii
J. virginiana – Eastern Red Cedar
- ‘Tripartita’
References
Phomopsis blight of junipers. U.S. Department of Agriculture Forest Service.
Focus on Plant Problems: Phomopsis Blight. University of Illinois Extension.
Juniper Twig Blights – Phomopsis and Kabatina – Shrubs. University of Maryland Extension.
Juniper Diseases & Insect Pests. Clemson Cooperative Extension.
Phomopsis Blight of Juniper. Missouri Botanical Garden.
Juniper Tip Blight. Adam Blalock and Dr. Fulya Baysal-Gurel. Tennessee State University.
Diseases of Trees and Shrubs. Sinclair, W.A., Lyon, H.H., and Johnson, W.T. Cornell University Press. Ithaca, New York. 1993.
Landscape Plant Problems: A Pictorial Diagnostic Manual. Byther, R.S., Foss, C.R., Antonelli, A.L., Maleike, R.R., and
Bobbitt, V.M. Washington State University Cooperative
Extension, 2000.
Très bon article !
Merci !
Catherine
Thank you for the positive comment. We are happy you found it useful.
Yikes, I’m sure this is what we have. Is it futile to just trim off the small brown shoots as they quickly appear? Would it be better at all to cut off the entire branch (although we’d have nothing left of our two big Chinese Junipers!)
Thanks so much!
Responding to your question about the trimming of the dead shoots on your juniper: the disease normally attacks the new season’s growth. You did not say whether you lived in the PNW, where our company is based, but we have had an overabundance of disease situations this spring and summer due to our nice temperatures and consistent moisture periods this season. If we get into some drier weather, most diseases should settle down.
Since the disease attacks the new growth, your older foliage and stems should be resistant to infection. So I would be hesitant to tell you to cut off the entire branch. But it is very important to try to cut off the infected foliage as soon as you see it.
If this has been a reoccurring problem, you may decide that the plants just need to be replaced in the future. If you do replace them, you would want to plant a different kind of plant or plant a juniper that shows more resistance to the disease. Just know that resistance means that if the weather conditions are right the plant can become infected.
Let me know if you need any more information from us. Have a great day!
Ladd Smith, In Harmony Co-owner
Thanks Ladd! I’m not in PNW but up in Toronto. For the last few years I assumed it was winter kill until I noticed things were getting brown well after the warm weather started, then I saw your article. The plants are huge now and still look nice. I’ll clip and hope!
What is the chemical treatment of the disease?
Our company uses a natural approach to plant problems in order to protect human health and the environment. Following that strategy, we don’t recommend chemical fungicides for phomopsis blight. We believe that a better approach, and one that will ultimately be more successful, is to use strategies such as planting resistant species, maintenance pruning and careful watering.
We have a full grown thuja ( weeping thread leaf arborvitae) that is dying or has died. We live in Oklahoma and after reading I think the tree has likely been infected since we moved in 2 yrs ago. We love the tree, and would like to replace with the same thing. We were unaware of Phomopsis until late June and missed the opportunity to treat. Is there anything we can do as we remove the one tree and plant another? Others in the neighborhood seem unaffected. Thank you!
Hello, we wanted to get back to you about your trees and a possible disease.
The 1st step is to get a soil test to see if it is actually phomopsis that you are seeing. I would recommend you contact your local extension agency, they can probably point you in the right direction for a disease soil test. The will probably will want you to send them some soil and some root matter.
If the soil test comes back negative, then you have no worries and can plant anything there you want. If the test comes back positive, you may want to think about another plant that is not susceptible to the disease. Your extension agency can also provide a list of non-susceptible plants that are good for your area.
Most of these soil diseases are always present in the soil. It is when the enviroment becomes condusive for the disease to take off that we can have problems. For phomopsis, saturated soils are the biggest challenge for plants because they can not get oxygen to their roots and the roots begin to rot. Without the ability to change the soil profile, if you planted another susceptible plant in the area, the chances are greater that the new plant’s roots will also become infected.
Good luck!
Ladd Smith
Co-Owner