Cause There are numerous leaf spots on Sambucus sp. but only a few have been reported in the PNW including Cercosporella prolificans and Septoria sambucina. A Ramularia sp. has been found by the OSU Plant Disease Clinic. Fungal leaf spots are generally encouraged by wet, rainy weather that keeps foliage wet for long periods of time. Most overwinter in plant debris.
Symptoms Leaf spots on a bush in the forest with Septoria were necrotic, tan to brown with a darker margin. Sometimes bull's eye-shaped with occasional dark fruiting bodies (pycnidia) near the center. Spots were scattered on the leaves and sometimes coalescing into larger spots. Leaves with numerous spots appeared to turn yellow and drop from the plant.
A leaf spot disease of elderberry in a home garden displayed large, irregular necrotic spots. Some necrotic spots had a yellow halo. Leaves with numerous spots became yellow and fell off the plant.
Cultural control
- Space or prune bushes to allow for good airflow. Avoid dense plantings and shaded areas.
- Avoid overhead watering that keeps plants wet for extended periods of time.
- Rake up and burn all leaves at season's end.
- Remove and destroy infected plant parts.
Chemical control
- Abound at 6 to 15.5fl oz/A. Do not apply with silicone-based surfactants. May be applied on the day of harvest. Group 11 fungicide. 4-hr reentry.
- Cabrio EG at 14 oz/A. May be used at harvest. Group 11 fungicide. 12-hr reentry
- Fontelis at 16 to 24 fl oz/A. Can be used day of harvest. Group 7 fungicide. 12-hr reentry.
- Omega 500 F at 20 fl oz /A. Do not use with an adjuvant or within 30 days of harvest. Group 29 fungicide. 12-hr reentry.
- Oso SC at 6.5 to 13 fl oz/A. May be applied on the day of harvest. Group 19 fungicide. 4-hr reentry. O
- Pristine at 18.5 to 23 oz/A. Do not use with any other tank additive. Can be used day of harvest. Group 7 + 11 fungicide. 12-hr reentry.
- Proline 480 SC at 5.7 fl oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-hr reentry.
- Propulse at 13.6 fl oz/A. Do not use within 7 days of harvest. Group 3 + 7 fungicide. 12-hr reentry.
- Quadris at 6 to 15.5 fl oz/A. Do not apply with silicone-based surfactants. May be applied on the day of harvest. Group 11 fungicide. 4-hr reentry.
- Quash at 2.5 oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-hr reentry.
- QuiltXcel at 14 to 21 fl oz/A. Do not use within 30 days of harvest. Sprayers should not be used on apples. Group 3 + 11 fungicide. 12-hr reentry.
- Switch 62.5 WG at 11 to 14 oz/A. May be used up to and including the day of harvest. Group 9 + 12 fungicide. 12-hr reentry.
Reference Hensel, K. 2017. Rust and leaf spot diseases on American elderberry plants. Doctoral dissertation, University of Missouri-Columbia.