Phomopsis Blight and Canker
Phomopsis spp., Diaporthe spp.
Overview
Phomopsis blight and canker refers to disease complexes caused by Phomopsis and related fungi on junipers, blueberries, eggplant, and many woody plants. Tip blight, stem cankers, and fruit rots often appear together in wet springs. The fungi fruit as tiny black pycnidia on dead tissue and splash to nearby shoots. Sanitation pruning, airflow, and protecting bloom or soft shoot periods with organic protectants when needed fit well with small-scale and ecological plantings.
Symptoms
Shoot tips brown and die back, sometimes looking scorched. Sunken cankers girdle twigs and larger stems, causing wilt above the lesion. Fruit develops soft rot with small black fruiting bodies on the surface. Yellowing and dieback progress from infected wood outward. On junipers, successive tip blighting can ruin ornamental form over a few wet seasons.
Environmental Conditions
Humid
Prevention
Buy clean nursery stock and inspect for tip dieback before planting. Space and prune for rapid drying after rain. Avoid overhead irrigation on susceptible crops. Remove dead wood each winter. On blueberries and similar fruits, time protective sprays for bloom and early fruit set in humid regions. Avoid mechanical injury to stems.
Management
Prune infected shoots during dry weather, cutting well into healthy wood, and destroy prunings. Disinfect shears between cuts on valuable plants. Improve canopy openness. Copper or other organic fungicides timed for wet spring periods and bloom (on fruit crops) reduce new infections. Remove fallen infected fruit and twigs. Replace chronically blighted junipers with more resistant species if the site stays wet.