Cherry Disease Management: Black Knot, Brown Rot, Leaf Spot, Canker, and Viral Control

Comprehensive Cherry Disease Management

Cherries face black knot, brown rot, Coccomyces leaf spot, Leucostoma canker, and necrotic ring spot virus. Effective management combines sanitation, fungicide timing, and variety selection.

Black Knot

Plowrightia morbosa (Apiosporina) causes dark brown/black hard swellings on twigs/branches; small initially, enlarging yearly, rough; olive-green felt-like growth each spring; branches girdled/die.

Management: Prune/destroy galls (several inches below) when found, especially dormancy. Remove unwanted Prunus. Trunk/large branch galls: cut out + 1 inch surrounding wood. Fungicide at green tissue, pre-bloom, and post-bloom.

Brown Rot

Monilinia fructicola causes flower collapse/browning; small twig cankers with gum; ripening fruit brown/shrivel with tan/gray spores; some mummies remain on tree.

Management: Fungicide at first blossom open and 70-90% bloom.

Coccomyces Leaf Spot

Blumeriella jaapii (Coccomyces) causes circular purple/reddish-brown spots (≤1/8 inch) early summer, increasing; shot-hole appearance; premature yellowing/leaf fall.

Management: Fungicide as leaves emerge in spring.

Leucostoma Canker

Leucostoma cincta or L. persoonii (Cytospora) causes branch dieback, multiple perennial cankers; gum accumulates in inner bark, erupts through cracks/lenticels, becomes blackened crust. Freeze-damaged and drought-stressed trees most susceptible.

Management: Infection any time. Growing tree walls off fungus; slowed/stopped growth = fungus invades. Prune cankered limbs. Promote tree vigor.

Necrotic Ring Spot

Virus causes delayed spring leafing on branches/whole tree; smaller/fewer leaves; light green spots (≤1/4 inch) with dark rings/lines; wavy margins, rough blades; spots die/fall out; bark splitting, branch dieback. Transmitted mechanically, grafting, seed, pollen.

Management: Destroy infected trees. Plums/other stone fruits also susceptible.

Integrated Cherry Health Program

Key strategies: rigorous black knot sanitation (pruning timing critical); brown rot fungicide timing (blossom stages); Coccomyces early-season protection; Leucostoma management through vigor promotion and canker pruning; necrotic ring spot eradication (destroy infected trees); and variety selection where resistance exists. The combination of fungal and viral diseases requires a multi-tactic, season-long approach.