The American elderberry shrub is a popular ornamental plant prized for its showy flowers, fruit production, and medicinal benefits. However, like all plants, elderberries are susceptible to fungal diseases that can diminish their health and appearance. In this comprehensive guide, we’ll explore techniques for effectively treating and preventing fungal problems on your American elderberry shrub.
Common Fungal Diseases of Elderberry
Several fungal pathogens can infect elderberry shrubs, causing spots rusts, mildews and blights. Some of the most common include
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Powdery mildew – Caused by Erysiphe spp., appears as white powdery coating on leaves and stems
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Leaf spot – Sphaceloma and Diplocarpon fungi lead to small, dark spots on foliage
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Rust – Puccinia bolleyana causes yellow/orange powdery galls on stems and leaves.
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Cankers – Fungi like Cryptosporella cause sunken dead areas on bark.
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Fire blight – Bacteria Erwinia amylovora infects flowers and shoots.
While rarely fatal, these diseases can diminish fruit production, vigor, and aesthetic appeal if left unchecked. Monitor shrubs frequently to identify issues early before they spread.
Cultural Practices to Prevent Fungal Diseases
Implementing smart cultural practices is the first line of defense against fungal diseases on elderberry shrubs:
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Choose disease-resistant elderberry cultivars when available.
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Prune shrubs regularly to improve airflow and light penetration.
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Space plants adequately to allow air circulation.
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Avoid overhead watering and don’t overcrowd plants.
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Clean up and remove fallen leaves and debris around plants.
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Use mulch and improve drainage to prevent waterlogged soil.
Safely Using Fungicides on Elderberry Shrubs
If diseases persist despite preventive measures, fungicide application may be warranted. Always follow label directions carefully:
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Organic options include neem oil, sulfur, and copper sprays. Test first for phytotoxicity.
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Conventional fungicides like myclobutanil, propiconazole, and tebuconazole are effective.
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Only treat affected areas and alternate chemicals to avoid resistance.
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Avoid spraying blooms to protect pollinators and only use elderberry fruit/flowers as food/medicine after an appropriate waiting period.
How to Treat Specific Fungal Diseases on Elderberry
For each disease, integrate cultural practices with targeted organic or chemical treatments:
Powdery Mildew
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Improve air flow and reduce water on leaves.
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Apply neem oil or potassium bicarbonate weekly as needed.
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Use trifloxystrobin or myclobutanil fungicides if severe.
Leaf Spot
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Promote good drainage and prune affected foliage.
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Spray copper-based fungicides after leaf emergence.
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Rotate trifloxystrobin, tebuconazole, or chlorothalonil for stubborn spot.
Rust
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Prune out infected galls. Disinfect tools between cuts.
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Eliminate nearby sedges that host the rust fungus.
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Apply mancozeb or trifloxystrobin at first sign of disease.
Fire Blight
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Prune out infected shoots well below diseased areas. Sterilize tools.
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Use preventive copper sprays at leaf emergence and flower bloom.
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Avoid excess nitrogen fertilization and overwatering.
Left unchecked, fungal diseases can quickly deflate the ornamental and edible value of American elderberry shrubs. But with close monitoring, cultural prevention, and strategic fungicide use only when necessary, you can maintain healthy, productive plants for years to come. Proper identification and prompt treatment are key to staying one step ahead of any fungal issues.
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Where does elderberry rust come from?
Elderberry rust is caused by the fungus Puccinia sambuci, also known as Puccinia bolleyana. The fungus overwinters in sedge debris, and spores produced in this debris blow to elderberry plants in the spring, leading to infection and gall formation. Spores produced in elderberry galls blow back to sedges, where infection of newly produced leaves (and other plant parts) occurs. These infections lead to spotting and to the formation of a third type of spore that reinfects sedges causing additional spotting. Late in the season a fourth type of spore is produced that serves as the overwintering phase of the fungus. Infection of both elderberries and sedges is favored by wet weather.
How do I save plants with elderberry rust?
Elderberry rust is not a lethal disease on either elderberry or sedge. When galls form on elderberry, simply prune these out. This will make elderberry plants more aesthetically pleasing and limit spread of the fungus to sedges. When pruning, cut branches four to six inches below each gall. Between cuts, decontaminate pruning tools by treating them for at least 30 seconds with 70% alcohol (e.g., rubbing alcohol straight out of the bottle), a spray disinfectant containing 60-70% active ingredient, or a 10% bleach solution (i.e., one part of a disinfecting bleach and nine parts water). If you decide to use bleach, be sure to rinse your tools thoroughly after you are done pruning and then oil them to prevent rusting, which can be caused by bleach use. Dispose of galls by burning (where allowed by local ordinance) or burying them.
This solution burns out all pests lichens and fungus on fruit trees
FAQ
How do you treat elderberry fungus?
How do you get rid of shrub fungus?
What is killing my elderberry bush?
What is the white stuff on my elderberries?
Is elderberry rust a fungal problem?
Rust is a common fungal problem in plants, but elderberry rust ( Puccinia bolleyana) is one of the uglier forms of it! This causes lesions and fungal sporulation on leaves but also can cause galls on the stems/canes of the plant.
How do I know if my elderberry has a fungus?
Look for discolored spots or blotches on the elderberry leaves to diagnose leaf and stem spots. Caused by a fungus, leaf and stem spots produce irregular patches that are usually yellowish or brown. Spot the symptoms of aphid infestations by looking for yellowed, curled and distorted leaves.
Do elderberry bushes need weeds?
Elderberry bushes like to have a clean growing space. It’s best to keep weeds down around your plants. By reducing the amount of debris around the plant, you’re increasing airflow and also ridding the area of spaces for pests and diseases to hide.
Do elderberry plants have bugs?
Don’t panic if you notice a couple of elderberry bugs hanging out on your plants. These are typically easy to remove with pesticides or avoid altogether with floating row covers. Some of the most common pests that you find on elderberry plants are cane borers, aphids, and thrips. These are all winged insects that feast on the leaves of your plants.