Scouting for diseases: Juniper tip blight

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

Cause:
Phomopsis juniperovora and Kabatina juniperi (fungi)

Hosts: Juniper and rarely arborvitae, cryptomeria and chamaecyparis are susceptible to infection by these fungi. Susceptibility varies widely among species and cultivars.

Symptoms: Both fungi produce similar symptoms; time of symptom appearance differs.

Phomopsis tip blight:
This fungus overwinters in small black fruiting bodies
(~ 0.5 mm in diameter) on dead stems and needles infected the previous year. Spores are released during warm, wet weather and spread primarily through rain splash and overhead irrigation. Symptoms are common during wet, spring weather but may be present whenever new growth is present.

Kabatina tip blight:
Infection occurs in fall, but symptoms don’t appear until early spring. Kabatina infects through wounds. Branch tips turn dull green then reddish-brown or yellow. Black fruiting bodies appear in small ash-gray lesions at the bases of the dead tips. Dieback occurs only in early spring. Juniper tips that have died from drought, dog urine or winter injury do not contain pycnidia and fade gradually from brown to green instead of having a sharp line dividing the dead and live tissue.

How it’s spread: Spores can be spread by rain or infested pruning tools.

Management:
Send a sample to MSU Diagnostic Services. Accurate diagnosis is made by looking at differences in spores. In general, avoid pruning when foliage is wet; avoid shearing or excessive wounding. When pruning out diseased plant tissue, disinfest pruning tools. Water early in the day to allow foliage to dry before nightfall. Avoid excessive fertilization, as it promotes succulent new growth. When installing new plantings, allow enough space between plants for good air circulation. Treatment timing and fungicide recommendations vary depending on which fungus is present.

Resources for additional information
Ohio State University Extension Factsheet, Phomopsis and Kabatina Tip Blights of Junipers, HYG-3056-96 online: http://ohioline.osu.edu/hyg-fact/3000/3056.htm

BP-29 Juniper Tip Blights Purdue University Cooperative Extension Service West Lafayette, IN 47907 online: http://www.agcom.purdue.edu/AgCom/Pubs/BP/BP-29.html.

Editor’s note: The information in this article is from MSU Extension publication E-2839, A Pocket IPM Scouting Guide for Woody Landscape Plants. The publication can be ordered through MSU Extension: http://ipm.msu.edu/woodylandscape.htm

Phomopsis
Phomopsis infections begin at or near the
branch tips of new growth and progress down
the stem toward the older growth. Branch tips
of infected new growth turn light green, then
brown, then ash-gray. New fruiting bodies
(pycnidia) can form within 3 to 4 weeks after
infection.

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