 |
 |
 |
 |
||
 |
 |
 |
|||
|
|
|
|
|
||
|
|
|
|||
 |
|
body |
Problem: Cercospora Needle Blight of Juniper - Cercospora sequoiae var. juniperi
Host Plant: Rocky Mountain juniper
Description: Cercospora needle blight, caused by the fungus Cercospora sequoiae var. juniperi, is potentially destructive in established juniper plantings. Repeated infections over several years may result in defoliation and tree death. The disease is most severe in areas with high summer humidities and frequent rains.
Symptoms of Cercospora needle blight first appear in late summer and fall on inner branch needles (those located nearest the main tree trunk) and toward the lower portion of the tree. Needles turn dull brown or red and eventually drop. Small fuzzy or hairy spore-bearing fungal structures, easily visible with a hand lens, form on the dead needles. Defoliation in succeeding years continues from the inner portion of the branch toward the tip, and from the bottom of the tree toward the top. Severely infected trees are open, spindly, and may appear as if they had been scorched by a fire.
Cercospora needle blight may occur on several juniper species. Rocky Mountain juniper is particularly susceptible and should not be planted in locations where the disease has previously been a problem. Most selections of eastern redcedar and Chinese junipers have good resistance to this disease. Proper tree spacing, which promotes good air movement and rapid drying of foliage, will also inhibit disease development.
Recommendations: Chemical control may be necessary on susceptible junipers during wet summers. Although symptoms of Cercospora needle blight appear in the fall, fungal infection of needles actually occurs in the summer. Therefore, make two fungicide applications in early June and again in early July. A third application in mid- to late July may be necessary during wet summers. Fungicide applications at other times are ineffective. Take care to cover the foliage thoroughly, especially the lower two-thirds of the tree crown. Yearly fungicide applications may not be required once the disease is controlled; however, carefully monitor trees for recurrence yearly.
References:
1. Juniper Diseases. K-State Research and Extension. Publication C-711.
Last Update: 05/06/2003
Extension Horticulture Home Page | Horticulture Information Center