Phomopsis Twig Blight
Diaporthe vaccinii
20 host plants · Fungal
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Twigs on junipers progressively die back from the branch tips downward, starting in spring as new growth begins. Infected branches show a grayish discoloration and dieback pattern. Small dark fruiting bodies (pycnidia) appear on dead twig tissue, producing spores that spread during wet weather. Environmental stress, winter damage, or wounding from mechanical injury often precedes symptom development. Severe infections can kill entire branches or even the plant.
Phomopsis twig blight on junipers is manageable with resistant cultivars and vigilant pruning. Plant varieties like Juniperus chinensis 'Pfitzeriana Aurea', J. sabina 'Arcadia', or J. scopulorum 'Silver King', which show better resistance than others. Prune out infected twigs immediately when you spot them, cutting well below the diseased area, and avoid wounding plants during establishment. Clean tools between cuts and manage water to avoid excess moisture on foliage that promotes spore germination.
Quick Reference
Management
Spring (April-May) during bud break and young shoot emergence. Peak: late April through May. New growth most vulnerable.
Cool wet spring (50-62°F) with 8+ hours leaf wetness. Phomopsis spp. favor cool maritime conditions. Rain-splash primary dispersal.
Cultural Controls
- Plant resistant cultivars such as Juniperus chinensis 'Pfitzeriana Aurea', 'Iowa', and 'Glauca'; J. sabina 'Arcadia', 'Broadmoor', and 'Skandia'; J. scopulorum 'Silver King'; J. virginiana 'Tripartita'.
- Prune and destroy infected twigs and branches promptly.
- Avoid wounding plants during cultivation or maintenance.
- Maintain good air circulation around plants to reduce humidity.
- Remove and destroy infected plant material to reduce inoculum sources.