Garden Q&A: Juniper tip blight spreads easily
Question: We have a hillside covered with green-mound juniper, and every year for the past several years, one or two of the bushes develop patches of brown foliage. We cut the brown off but would like to know if there is anything else we could do. We are afraid it might spread and the whole hillside will be affected. Any suggestions you have would be greatly appreciated.
Answer: Junipers are inclined to develop a fungal disease known commonly as juniper tip blight, which causes randomly located, individual branches to yellow, brown, and eventually die. This disease is caused by one of three organisms — Phomopsis juniperovora, Kabatina juniperi, or Sclerophoma pythiophila. Young plants are more severely affected, but older plants can withstand quite a bit of damage.
In addition to many species of juniper being susceptible, so too are arborvitae, white cedar, and cypress, among several other evergreens.
Treatment involves the careful and regular removal of infected branches during dry summer weather only. To prevent spreading the fungal spores, keep your clippers clean, water only in the morning, maintain adequate fertility (but do not over fertilize), provide the plants with good air circulation, and only work around the plants for any maintenance needs during dry, warm weather.
It is exceedingly important that your pruners are sharp and meticulously clean before any pruning takes place. The blades should be dipped in a 10 percent bleach solution or wiped off with rubbing alcohol between each and every cut. Pruning an infected plant and then moving on to a healthy one before cleaning your clippers is a recipe for disaster. You'll also want to be sure to wash your gardening gloves before working around infected plants.
Potassium bicarbonate fungicides can help prevent the spread of this blight (depending on which organism is the culprit), but the cultural practices outlined above are often enough to stave off major infections.
Every two or three years, you should consider fertilizing your junipers with an evergreen-specific granular fertilizer. I like Espoma's HollyTone for my evergreens, as it helps maintain the acidic soil conditions evergreens prefer, but your local garden center may have other evergreen-specific options as well.
It is also worth noting that branch dieback also can occur on junipers exposed to salt splash and dog urine. If salt splash is the culprit, the browning will occur over broader areas mostly at road edges. If Fido is the culprit, the browning will occur in a patch only where the dog has repeatedly relieved itself.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is www.jessicawalliser.com.
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