{"id":34708,"date":"2025-10-09T12:30:59","date_gmt":"2025-10-09T16:30:59","guid":{"rendered":"https:\/\/www.purdue.edu\/fnr\/extension\/?p=34708"},"modified":"2026-06-30T15:02:07","modified_gmt":"2026-06-30T19:02:07","slug":"fungal-decay-of-ash-trees-plr","status":"publish","type":"post","link":"https:\/\/www.purdue.edu\/fnr\/extension\/fungal-decay-of-ash-trees-plr\/","title":{"rendered":"Fungal Decay of Ash Trees, Purdue Landscape Report"},"content":{"rendered":"

Purdue Landscape Report<\/em><\/a>: By now, the emerald ash borer (EAB) invasion is an old story for landscapes and forests in the Midwest. Since EAB was first found in North America in 2002 more millions of ash trees than we can know have died and this tiny insect continues to kill ash in an ever widening zone that currently includes 37 US states and 6 Canadian provinces. Arborists and landscape managers continue to protect valuable ash trees by use of systemic insecticides, typically applied via trunk injection every 2-3 years.<\/p>\n

While EAB is the overarching threat, ash survival may also be threatened by wood decay fungi, which may colonize insect exit holes, injections sites and other wounds. The most common decay fungi we see in the lab are Perenniporia<\/em> and Fomitopsis<\/em>.<\/p>\n

Perenniporia fraxinophila<\/em> is the most frequently reported wood decay fungus on ash and causes a heart rot that contributes to loss of structural integrity of the tree. Infection sites tend to be high on the tree and may be easily overlooked until decay is advanced. The fungal structure is perennial, expanding each year, and may be confused with Ganoderma applanatum<\/em>, the artist\u2019s conk. The upper surface turns black or brown with age and the underside is white with pores instead of gills.<\/p>\n

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\n\"Figure
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Figure 1: Upper ash branches colonized by a suspected Perenniporia<\/em> sp. (PLR)<\/figcaption><\/figure>\n<\/div>\n
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\n\"Figure
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Figure 2: Fungal conks of a suspected Perenniporia<\/em> sp., beginning to emerge from decaying ash branches. (PLR)<\/figcaption><\/figure>\n<\/div>\n
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\n\"Figure
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Figure 3: Fungal conks of a suspected Perenniporia<\/em> sp., beginning to emerge from decaying ash branches. (PLR)<\/figcaption><\/figure>\n<\/div>\n<\/div>\n

 <\/p>\n

In the last few years, we have had a few samples of a similar fungus colonizing the trunk and base of ash trees, often near injection sites. Initially we were unable to identify the fungus, but DNA analysis revealed the fungus was a Fomitopsis<\/em> species. This fungus develops a shallow shelf structure with white top and tan underside.<\/p>\n

Fungal decay presents a greater risk to ash because it lacks the preservative enriched heartwood found in oak, walnut and other hardwoods that tends to slow down internal spread of fungi. Even fungi that initially invade dead areas of ash may rapidly colonize and degrade stem and trunk tissue.<\/p>\n

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\n\"Figure
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Figure 4: Fomitopsis sp. colonizing the trunk of ash trees damaged by EAB. (PLR)<\/figcaption><\/figure>\n<\/div>\n
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\n\"Figure
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Figure 5: Fomitopsis sp. colonizing the trunk of ash trees damaged by EAB. (PLR)<\/figcaption><\/figure>\n<\/div>\n
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Figure 6: Fomitopsis sp. colonizing the trunk of ash trees damaged by EAB. (PLR)<\/figcaption><\/figure>\n<\/div>\n<\/div>\n

 <\/p>\n

Fungal decay also disrupts vascular tissues in the stems and trunk, which further limits the movement and effectiveness of insecticide injections, so that infected trees may face greater damage from EAB. When found on small side branches the infection might be successfully pruned out, but in most cases the decay is in major branches or the trunk, which means the tree will need to be removed. If your ash trees that are being regularly treated for EAB but continue to show thinning and decline, check for these fungal invaders, they may be partly responsible.<\/p>\n

View the original article on the Purdue Landscape Report website: Fungal Decay of Ash Trees<\/a>.<\/p>\n

Subscribe and receive the newsletter: Purdue Landscape Report Newsletter<\/a>.<\/p>\n

Resources:
\n<\/strong>Diplodia Tip Blight of Two-Needle Pines<\/a>, The Education Store, Purdue Extension resource center
\nBoxwood Blight<\/a>, The Education Store
\nDisease of Landscape Plants: Cedar Apple and Related Rusts on Landscape Plants<\/a>, The Education Store
\nPlanting Your Tree Part 1: Choosing Your Tree<\/a>, Purdue Extension – Forestry & Natural Resources (FNR) YouTube Channel
\nTree Planting Part 2: Planting a Tree<\/a>, Purdue Extension – FNR YouTube Channel
\nFind a Certified Arborist<\/a>, Trees are Good-International Society of Arboriculture (ISA)
\nVideo: Step by Step to Find an Arborist<\/a>, Trees are Good-International Society of Arboriculture (ISA)
\nProfessional Forester<\/a>, Indiana Forestry Woodland Owners Association
\nDistrict Forester<\/a>, Indiana Department of Natural Resources, 10+ acres
\nTrees and Storms: Understanding Damage, Risk and Recovery<\/a> \u2013 Got Nature? Blog, Purdue Extension \u2013 FNR
\nWhy Is My Tree Dying?<\/a> \u2013 Got Nature? Blog, Purdue Extension \u2013 Forestry and Natural Resources
\nTree Risk Management<\/a> \u2013 Got Nature? Blog, Purdue Extension \u2013 FNR
\nTree Pruning Essentials, Publication<\/a>\u00a0&\u00a0Video<\/a>, The Education Store
\nTree Wound and Healing<\/a>, Got Nature? Blog, Purdue Extension \u2013 FNR
\nWhat are Invasives Species and Why Should I Care?<\/a>, Got Nature? Blog, Purdue Extension \u2013 FNR
\nSubscribe<\/a>\u00a0\u2013 Purdue Extension-FNR YouTube Channel<\/p>\n

Tom Creswell<\/a>, Plant & Pest Diagnostic Laboratory Director
\nPurdue Botany and Plant Pathology<\/p>\n","protected":false},"excerpt":{"rendered":"

Purdue Landscape Report: By now, the emerald ash borer (EAB) invasion is an old story for landscapes and forests in the Midwest. Since EAB was first found in North America in 2002 more millions of ash trees than we can know have died and this tiny insect continues to kill ash in an ever widening […]<\/p>\n","protected":false},"author":62,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[870,42,53,622],"tags":[331,60,913,895,408,71,1867,495],"class_list":["post-34708","post","type-post","status-publish","format-standard","hentry","category-disease","category-forestry","category-urbanforestry","category-woodlands","tag-ash-tree","tag-forestry","tag-fungal-disease","tag-purdue-landscape-report","tag-trees","tag-urban-forestry","tag-wood-decay","tag-woodlands","audience-for-enthusiasts","audience-for-homeowners","audience-for-landowners","audience-for-professionals"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/posts\/34708","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/users\/62"}],"replies":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/comments?post=34708"}],"version-history":[{"count":16,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/posts\/34708\/revisions"}],"predecessor-version":[{"id":41761,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/posts\/34708\/revisions\/41761"}],"wp:attachment":[{"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/media?parent=34708"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/categories?post=34708"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/tags?post=34708"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}