Twig Blight of Juniper

Dr. John F. Baniecki
WVU Extension Service
Plant Pathology and
Entomology Specialist
August 2000

Juniper twig blight, also known as Phomopsis twig blight, caused by the fungus Phomopsis juniperovora, infects twigs of junipers, crytomeria, chamaecyparia, and arborvitae. This disease could be confused with cold injury or spider mites.

Symptoms

Needles turn dull green to light brown to reddish-brown on smaller branches or twigs scattered over the plant. Twigs gradually die back from the tips. Old and new leaves and twigs may be involved. Tiny black dots usually appear on infected leaves or stems (seen with 10 x magnifying lens). Red cedars are especially susceptible to this disease. On highly susceptible hosts, the fungus may invade and girdle larger stems, resulting in browning and death of major branches. In very severe cases, entire plants may be killed.

Varieties having reported resistance are the spiny Greek juniper (J. excelsa var. stricta), Keteller red cedar (J. virginiana var. Keteleeri) and the Kill juniper (J. virginiana var. pyramidiformis hilli).