Heterobasidion Root Disease

Heterobasidion annosum

78 host plants

Last updated

Data Maturity Structured

This profile synthesizes data from multiple published sources. Expert field review is in progress.

Heterobasidion root rot affects conifers in cool, moist forests, particularly spruce, fir, hemlock, and lodgepole pine. Infected trees show gradual decline as the fungus colonizes the root system and lower trunk, slowly girdling the tree and cutting off water and nutrient movement. Infection spreads through root contact between trees and through spores that land on freshly cut stump surfaces, making harvest timing and site conditions critical factors in disease development.

This disease takes years to kill a tree, making early detection difficult in ornamental settings. The practical impact concentrates in forestry and dense conifer plantings where tree-to-tree contact creates highways for fungal spread. Minimizing fresh wounds, avoiding harvest during spore release seasons, and spacing trees to prevent root grafting reduce risk; once infection occurs in a stand, management options are limited.

Quick Reference

Causal Agent
Heterobasidion annosum
Host Plants
78
Spread
wind
Favorable Conditions
Infection requires fresh stump surfaces exposed to airborne basidiospores. Pe...

Management

Vulnerability Window

Fresh stump surfaces present peak vulnerability to spore infection during spore season (June–Oct), with highest risk June–Aug. Once spores establish in stumps, mycelial growth into adjacent roots occurs Oct–May (cool season) when soil moisture is high. Already-infected trees show progressive internal decay year-round, but visible symptoms (crown thinning, growth loss) typically become apparent 3–10 years post-infection. Replanted sites where infected stumps remain underground present permanent infection risk to newly planted conifers. BBCH 10–89 (emergence through dormancy) for healthy trees; risk is continuous once roots contact infected wood.

What Triggers Infection

Infection requires fresh stump surfaces exposed to airborne basidiospores. Peak spore dispersal occurs in summer and fall (June–Oct in Pacific Northwest); spore concentration is highest on warm, humid days. Newly cut stump surfaces are vulnerable for weeks to months after cutting, depending on weather (spore availability and moisture). Infection is most likely when stump cutting occurs during peak spore season. Spread via root contact occurs in moist, cool soil (Oct–May in Pacific Northwest); the fungus is most active in soil temperatures 40–60°F. Stressed trees with root contact to infected stumps/roots are at higher risk. Spread within infected trees is slow and temperature-dependent; cooler winters slow colonization rate.

Cultural Controls

  • Prevention is the primary strategy. Avoid stump exposure during peak spore season (June–Oct). If cutting must occur in summer, treat freshly cut stump surfaces with approved fungicide within hours of cutting, or coat heavily with paint/sealant to prevent spore entry.
  • Remove stumps and large root fragments from newly cleared land. Leave sites fallow for 1–2 years before replanting susceptible conifers if stumps cannot be removed.
  • When possible, delay replanting until spore season has passed (plant Nov–May). Avoid replanting directly over buried infected stumps.
  • In established plantations with infected trees, remove and stump-treat to reduce inoculum.
  • Do not move infected wood or chips to clean areas; the fungus is present in infected sapwood and can remain viable in stored wood.

Host Plants (78)

Abies alba European Silver Fir, Common Silver Fir Abies amabilis Pacific Silver Fir Abies balsamea Balsam Fir Abies concolor White Fir, Colorado Fir Abies delavayi Delavay's Fir Abies grandis Grand Fir Abies koreana Korean Fir Abies lasiocarpa Subalpine Fir Rocky Mountain Fir, Alpine Fir Abies magnifica California Red Fir, Red Fir, Slivertip Fir Abies nordmanniana Nordmann Fir, Caucasian Fir Abies numidica Algerian Fir Abies pindrow West Himalayan Fir, Pindrow Fir Abies pinsapo Spanish Fir, Spanish Pin Fir Abies pinsapo subsp. marocana Moroccan Fir Abies procera Noble Fir Picea abies Norway Spruce Picea abies var. pendula Weeping Norway Spruce, Pendulous Norway Spruce Picea asperata Dragon Spruce Picea breweriana Brewer Spruce, Brewer's Weeping Spruce Picea engelmannii Engelmann Spruce Picea gemmata Szechwan Spruce Picea glauca White Spruce, Canadian Spruce, Skunk Spruce Picea koyamae Koyama's Spruce, Yatsugatake-tohi [Japanese] Picea mariana Black Spruce, Bog Spruce, Swamp Spruce Picea omorika Serbian Spruce Picea orientalis Caucasian Spruce, Oriental Spruce Picea pungens Colorado Spruce Picea pungens var. glauca Colorado Blue Spruce Picea rubens Red Spruce Picea sitchensis Sitka Spruce Picea wilsonii Wilson's Spruce Pinus albicaulis Whitebark Pine, Scrub Pine, White Pine Pinus aristata Bristlecone Pine, Rocky Mountain Bristlecone Interior Bristlecone Pinus attenuata Knobcone Pine Pinus banksiana Jack Pine, Scrub Pine, Banksian Pine, Hudson Bay Pine Pinus bungeana Lacebark Pine, Whitebark Pine, Baipi Song Pinus canariensis Canary Island Pine Pinus cembra Swiss Stone Pine Pinus contorta Lodgepole Pine Pinus contorta var. contorta Shore Pine Pinus contorta var. latifolia Rocky Mountain Lodgepole Pine Pinus coulteri Coulter Pine, Bigcone Pine Pinus densiflora Japanese Red Pine Pinus edulis Pinyon Pine, Piñón Pine, Two-needle Pinyon Colorado Pinyon Pinus elliottii Slash Pine, Swamp Pine Pinus flexilis Limber Pine, Rocky Mountain White Pine Pinus halepensis Aleppo Pine, Jerusalem Pine Pinus heldreichii Bosnian Pine, Snakeskin Pine Pinus jeffreyi Jeffrey Pine, Western Yellow Pine, Bull Pine Pinus kwangtungensis Kwangtung Pine, Guangdong Pine Pinus lambertiana Sugar Pine Pinus leucodermis Bosnian Pine Pinus monophylla Singleleaf Pinon Pine, One-leaved Pine Pinus monticola Western White Pine Pinus mugo Mugo Pine Pinus mugo var. pumilio Mugo pine, Dwarf Mugo pine Pinus nigra Austrian Pine Pinus parviflora Japanese White Pine Pinus parvifola Pinus parvifola Pinus pinaster Maritime Pine, Cluster Pine, Turpentine Pine Pinus pinea Italian Stone Pine, Umbrella Pine Pinus ponderosa Ponderosa Pine, Western Yellow Pine Pinus pumila Japanese Stone Pine, Dwarf Siberian Pine Pinus radiata Monterey Pine Pinus resinosa Red Pine Pinus sabiniana Gray Pine, Foothill Pine Pinus strobiformis Southwestern White Pine, Mexican White Pine, Chihuahua White Pine Pinus strobus Eastern White Pine Pinus sylvestris Scots Pine, Scotch Pine Pinus thunbergii Japanese Black Pine Pinus virginiana Virginia Pine, Scrub Pine, Jersey Pine Pinus wallichiana Himalayan Pine, Bhutan Pine Pinus yunnanensis Yunnan Pine Tsuga canadensis Canadian Hemlock, Eastern Hemlock Tsuga canadensis var. pendula Weeping Hemlock Tsuga diversifolia Northern Japanese Hemlock Tsuga heterophylla Western Hemlock Tsuga mertensiana Mountain Hemlock