Cause The fungus Phomopsis juniperovora is found most often in western Oregon. Kabatina juniperi also causes a tip blight but is rare in western Oregon. Kabatina tip blight is more common in eastern Washington and throughout nursery markets east of the Rocky Mountains. Cultivars differ in susceptibility to both fungi. J. chinensis 'Pfitzeriana Aurea' is considered resistant to both. Mostly a nursery problem and not present in the landscape as much.
Time and location of infection also differ. Phomopsis infection occurs whenever foliage is young and moisture and humidity are high-generally, spring. Older, mature foliage is resistant to infection. Excessive pruning or shearing in summer will stimulate new, succulent growth that is highly susceptible. Kabatina infection is thought to occur in fall and often is associated with wounds, insect feeding, or mechanical damage.
Symptoms Both fungi cause a foliar blight and tip dieback, which are difficult to separate. Phomopsis-affected foliage first turns dull red or brown and finally ash-gray. Small gray lesions often girdle branch tips and kill the foliage beyond the diseased tissue. Small, black, fruiting bodies (pycnidia) develop in lesions. Most blighting is on the terminal 4 to 6 inches of branches. Repeated blighting in early summer can result in abnormal bunching of shoots, which may resemble a witches' broom. Young trees or shrubs may be stunted with discolored foliage and may eventually die. Symptoms of Kabatina infection generally are before those of Phomopsis. The ends of branches turn dull green then red or yellow. Small ash-gray to silver lesions dotted with small, black, fruiting bodies are visible at the base of the discolored tissue. Generally, this fungus does not result in extensive branch dieback or tree death, which could indicate a root problem.
- Prune out and burn affected twigs and branches.
- Avoid wounding twigs.
- Avoid irrigating in evening. Keep plants as dry as possible consistent with good growth.
- Do not overfertilize.
- Space plants for good air circulation.
- Grow resistant plants.
- Select cuttings only from disease-free stock plants.
Chemical control Spray at 2-week intervals in spring, beginning when growth starts. Additional applications may be needed after pruning or shearing when new growth is stimulated.
- Heritage at 1 to 4 oz/100 gal water plus a non-silicone-based wetter-sticker. 4-hr reentry.
- Kocide 3000 at 0.75 to 1.75 lb/A. 48-hr reentry. O
- Mancozeb-based products can be used as mixing partners and provide some protection. 24-hr reentry.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
- Pentathlon DF at 1 to 2 lb/A or per 100 gal water.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
- Phyton 27 at 1.3 to 2.5 oz/10 gal water. 24-hr reentry.
- Propiconazole-based products.
- Banner MAXX at 5 to 8 fl oz/100 gal water. 12-hr reentry.
- Infuse at 1 Tablespoon/gal water. H
- ProPensity 1.3 ME at 5 to 8 fl oz/100 gal water. 24-hr reentry.
- Thiophanate-methyl-based products. 12-hr reentry.
- Cleary's 3336 WP at 24 oz/100 gal water.
- Halt (by ferti-lome) is registered for home use. H
- Tourney 50 WDG at 1 to 4 oz/100 gal water. 12-hr reentry.
- Zyban WSB at 36 oz/75 gal water. Not to be confused with the smoking cessation drug. 12-hr reentry.
Reference Punithalingam, E. and I.A.S. Gibson. 1973. Phomopsis juniperovora. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 370.