Juniper Twig Blight: Phomopsis vs. Kabatina Identification and Control

Overview

Junipers (Juniperus spp., red cedars) are susceptible to twig tip death. Most severe in nursery stock/seedlings grown closely; established plants also attacked. Two fungi cause this: Phomopsis juniperovora and Kabatina juniperi. Microscopic exam of diseased tissue/spores required for differentiation.

Symptoms

• Spring: light green developing foliage turns brown at tips of small branches.
• Dead foliage may turn tan/ash gray with small black dots (spore structures) in dead needles.
• Cankers (sunken dead areas) form at junction of living/dead twig parts.

Phomopsis juniperovora

Attacks foliage then invades stems anytime during year. Branches up to 0.4" (1 cm) diameter girdled. Infection to new spores: as short as 3 weeks. At moderate temps (61–79°F / 16–26°C) with wet foliage, spore germinates and invades needle in 7 hours.

Phomopsis Twig Blight Management

• Do not purchase plants with dead/dying twigs.
• Plant where air circulation allows quick foliage drying after dew, rain, or sprinkler irrigation. Do not crowd. Avoid sprinkler irrigation if possible.
• Prune infected branches in dry weather.
• Apply fungicide when new growth begins and conditions are wet. Protect spring and fall growth. Pruning at other times may stimulate new growth. Sprays not needed in dry weather.
• Plant resistant varieties:

J. chinensis	J. communis	J. horizontalis	J. sabina	J. squamata
Chinese juniper	Common juniper	Creeping juniper	Savin juniper	Western red cedar
fimina aureo-spica	plumosa	broadmoor	campbellii	Iowa
depressa plumosa aurea	knap hill	fargesii	keteleeri	hispanica
prostrata		pfitzeriana aurea	hulkjaerhus
pumila rubusta		prostrata aurea
sargentii		repanda
sargentii glauca		saxatilis
shoesmith		suecica

J. scopulorum	J. virginiana
Western red cedar	Red cedar
silver king	tripartita

Kabatina juniperi

Blight occurs in spring; infection suspected previous fall. Controlled experiments: only plants with wounded foliage infected. In nature, insect feeding sites may provide entry.

Kabatina Blight Management

1. Water and care for plants to promote vigor and prevent foliage damage.
2. Protect from insect attack.
3. Prune infected branches in dry weather.
4. Fungicides may assist if applied late summer and fall.

References

• Hartman, J. 1982. Juniper Diseases. In Diseases of Woody Ornamental Plants and Their Control in Nurseries. R.K. Jones & R.C. Lambe, eds. NCSU AG-286. pp. 60-61.
• Peterson, G.W. 1981. Pine and Juniper Diseases in the Great Plains. USDA Forest Service Gen. Tech. Rep. RM-86. pp. 37-40.

Prepared by Gary W. Moorman, Professor of Plant Pathology.