Pest & Disease Anthracnose

Anthracnose

Discula fraxinea

What is Anthracnose (Discula fraxinea)?

Anthracnose caused by Plagiostoma fraxini (Asexual: Discula fraxinea) is a fungal disease affecting ash trees. It is distributed in regions such as the Pacific Northwest. The disease primarily targets young tissues, causing small water-soaked spots that rapidly merge into brown or tan blotches on distorted leaves. Infected leaves may exhibit necrotic spots, and severe cases can lead to defoliation and dieback in lower branches.

How does Anthracnose (Discula fraxinea) occur?

Ash dieback spreads through spores that infect susceptible ash trees. When conditions are favorable, spores germinate, penetrate leaves, and cause symptoms like leaf spots, wilting, and defoliation. It thrives in moderate temperatures with rain or humidity and extended leaf wetness. During reproduction, the fungus produces new spores (conidia) within acervuli on infected leaves. Released spores can be dispersed by wind, rain, or other means to infect new ash trees or susceptible plant parts, continuing the cycle.

Symptoms

1 - Tree Health Decline

The disease can weaken ash trees by causing defoliation, reduced growth, and declining tree health. This can increase vulnerability to other pests, diseases, or environmental stresses.

3 - Soil Nutrient Cycling

When ash trees are affected by Anthracnose, their leaf litter and organic matter input to the soil decrease. This can disrupt nutrient cycling processes, potentially affecting the composition and fertility of the soil.

4 - Carbon Sequestration

Ash trees contribute to carbon sequestration by absorbing carbon dioxide from the atmosphere. The loss of ash trees due to Anthracnose reduces the capacity of affected areas to sequester carbon, potentially impacting the local carbon balance.

5 - Landscape and Economic Impacts

Anthracnose can have significant aesthetic and economic impacts, particularly in areas where ash trees are valued for landscaping, timber, or other commercial purposes. The loss of healthy ash trees can require costly removal and replacement efforts.

Solutions

1 - Plant Selection and Resistant Cultivars

Select ash tree varieties that are known to be resistant to Anthracnose, as they are less likely to be affected by the disease. If Anthracnose is prevalent in your area, consider planting tree species other than ash that are not susceptible to the disease.

3 - Cultural Control

• Rake and dispose of fallen leaves to reduce the source of infection. • Prune and remove dead twigs and branches, improving air circulation and reducing disease spread. • Ensure proper watering practices to promote tree vigor. • Implement a balanced fertilization program based on soil test results. • Apply mulch around the base of the tree to conserve moisture and suppress weed growth.

5 - Sanitation and Removal of Infected Plant Material

Remove fallen leaves and debris from around the base of ash trees, as they can harbor fungal spores and promote disease development. Dispose of the debris properly. Disinfect pruning tools and equipment after each use, especially when working with infected trees.

Susceptible Species

Flamingo Boxelder

Kelly's Gold Boxelder

Japanese Maple

Suminagashi Japanese Maple

River Birch

River Birch (clump)

Summer Cascade Weeping River Birch

Kashmir Deodar Cedar

Eddie's White Wonder Flowering Dogwood

Cherokee Brave Flowering Dogwood

Cherokee Chief Flowering Dogwood

Cherokee Daybreak Flowering Dogwood

Cherokee Princess Flowering Dogwood

Cherokee Sunset Flowering Dogwood

Red Flowering Dogwood

Cornelian Cherry Dogwood

Golden Cornelian Cherry Dogwood

Variegated Cornelian Cherry Dogwood

Fallgold Black Ash

Leprechaun Green Ash

Patmore Green Ash

Sweet Gum

Round Leaf Sweet Gum

Silver King Sweet Gum

Slender Silhouette Sweet Gum

Worplesdon Sweet Gum

Tuliptree

Arnold Tuliptree

Yellow Variegated Tuliptree

Fastigiatum Tuliptree

Alexandrina Saucer Magnolia

Rustica Rubra Magnolia

horse chestnut

horse chestnut

snapdragon

European white birch

silver birch

false aster

false aster

false chamomile

false aster

camellia

Siberian peashrub

rose peashrub

tatarian dogwood

flowering dogwood

flowering dogwood

flowering dogwood

flowering dogwood

flowering dogwood

flowering dogwood

flowering dogwood

flowering dogwood

flowering dogwood

flowering dogwood

flowering dogwood

mountain dogwood

red twig dogwood

yellow twig dogwood

Washington hawthorn

common calabash tree

winter squash

winter squash

winter squash

summer squash

Kashmir cypress

winter creeper

white ash

white ash

white ash

European ash

European ash

European ash

Manchurian ash

flowering ash

green ash

pumpkin ash

blue ash

ash

English ivy

ashy sunflower

common hop

common St. John's wort

black walnut

ashe juniper

seashore mallow

common privet

Chinese tulip tree

big blue lilyturf

star magnolia

spearmint

oriental plane tree

common pear

white oak

scarlet oak

pin oak

pin oak

willow oak

English oak

English oak

English oak

red oak

weeping willow

dragon's claw willow

rough goldenrod

mountain ash

American mountain ash

European mountain ash

mountain ash

snowberry

ash-colored speedwell

David viburnum

southern prickly-ash

Oregon Ash

Red-Flowering Currant

Vine Maple

variegated bulbous oat grass

silverleaf dogwood

Silver King euonymus

Idaho fescue

narrow-leafed ash

Transvaal daisy

Oregon grape

peppermint

London plane

Garry oak

tomato

Pink Pagoda mountain ash

piggyback plant

Pink Dawn chitalpa

Seashore False Bindweed

Eyelash Fern

Red Ash

Black Calabash

Bigleaf Black Calabash

Wild Cashew

Cashew Nut

Ashitaba

Siberian Peashrub

Mandarin Plant

Cashmere (Cashmir) bouquet

Chinese Glory Bower

Calabash Tree

Blue Olive Berry

Manna Ash

Seashore Mangosteen

Ash sheora

Taffeta Plant

Urus mane

Urus mane

Calabash Nutmeg

Monodora

Ashanti Blood

Wild Sweet Calabash

Sweet Calabash

Telegraph Pole Tree

Hop Tree

Amargo

Ashoka Tree

Ashoka Tree

Chayote

Walking Palm

White Satin Ash

Roly Poly Satinash

West Indian Lilac

Washingtonia

Ashwagandha

American Prickly Ash

Moro Blood Orange