{"id":16198,"date":"2020-11-24T22:38:44","date_gmt":"2020-11-24T22:38:44","guid":{"rendered":"https:\/\/www.purdue.edu\/fnr\/extension\/?p=16198"},"modified":"2025-07-30T16:03:26","modified_gmt":"2025-07-30T20:03:26","slug":"tubakia-and-bur-oak-blight","status":"publish","type":"post","link":"https:\/\/www.purdue.edu\/fnr\/extension\/tubakia-and-bur-oak-blight\/","title":{"rendered":"Tubakia and Bur Oak Blight"},"content":{"rendered":"

Purdue Landscape Report<\/a>: Tubakia leaf spot, caused by the fungus\u00a0Tubakia<\/em>, is the disease we find more commonly on oak than any other. Throughout the world, there are 11 species of\u00a0Tubakia<\/em>\u00a0known to infect oak, with\u00a0Tubakia dryina<\/em>\u00a0(previously known as\u00a0Actinopelte dryina<\/em>) being the most commonly encountered species in our landscapes. Apple, ash, black gum, chestnut, elm, maple, and redbud are all reported as hosts of\u00a0Tubakia<\/em>\u00a0species, but oaks are the most frequently and severely affected. Among the oaks, the red oak group, specifically red, pin, and black oaks, are reported to be more susceptible to infection compared to those in the white oak group.<\/p>\n

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Figure 2: Oak leaf with circular shaped Tubakia leaf spots along with extensive veinal necrosis.<\/p><\/div>\n

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Figure 1: Oak leaf with irregularly shaped Tubakia leaf spots and veinal necrosis.<\/p><\/div>\n<\/div>\n

Leaf spots appear in mid to late summer (July \u2013August) as small circular to irregular tan, red-brown, to dark brown spots (Figure 1, 2) that expand to approximately the size of a dime overtime, but can coalesce, forming large areas of necrotic tissue (Figure 3) . When a spot reaches a leaf vein it expands very quickly, causing a necrotic streak along the vein, and can cause blighting of most of the leaf (Figure 4, 5). Trees under stress from other causes will frequently exhibit more severe leaf spotting compared to healthier trees. Premature defoliation can occur in these situations.<\/div>\n
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Figure 3: Marginal blighting due to coalescing spots and veinal necrosis.<\/p><\/div>\n<\/div>\n

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Figure 5: Blighting of large leaf area caused by veinal infection by Tubakia.<\/p><\/div>\n<\/div>\n

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Figure 4: Typical Tubakia leaf spot symptoms illustrating how the fungus spreads along leaf veins.<\/p><\/div>\n<\/div>\n

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The pathogen produces conidia within shield shaped structures called pycniothyria (Figure 6) which can be found on both the top or bottom surface of the leaf and along veins (Figure 7). These structures are very small and can only be seen with a 40x or stronger hand lens. The fungus overwinters on fallen leaves and on dead stems which act as the source of inoculum for the next year. During early spring, spores are spread by wind and water splash dispersal (rain) to healthy new foliage. However, it takes time for symptoms to develop throughout the season, depending on tree stress and environmental conditions (warm wet weather favors spread).<\/p>\n<\/div>\n

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For full article view: Purdue Landscape Report<\/a>, Purdue Landscape Report.<\/p>\n<\/div>\n

Resources:<\/strong>
\nDiseases of Landscape Plants: Leaf Diseases<\/a>, The Education Store, Purdue Extension resource center
\nConsumer Horticulture: Fertilizing Woody Plants<\/a>, The Education Store
\nTree Disease; Oak Wilt in Indiana<\/a>, The Education Store
\nDiseases of Soybean: Frogeye Leaf Spot<\/a>, The Education Store
\nBur Oak<\/a>, Purdue Arboretum Explorer
\nBur Oak<\/a>, Native Trees of Indiana River Walk, Purdue Fort Wayne
\nFind an Arborist<\/a>, TreesAreGood.org<\/div>\n

John Bonkowski<\/a>, Plant Disease Diagnostician
\nPurdue Department of Botany and Plant Pathology<\/p>\n

Tom C Creswell<\/a>, Clinical Engagement Professor – PPDL
\nPurdue Department of Botany and Plant Pathology<\/p>\n","protected":false},"excerpt":{"rendered":"

Purdue Landscape Report: Tubakia leaf spot, caused by the fungus\u00a0Tubakia, is the disease we find more commonly on oak than any other. Throughout the world, there are 11 species of\u00a0Tubakia\u00a0known to infect oak, with\u00a0Tubakia dryina\u00a0(previously known as\u00a0Actinopelte dryina) being the most commonly encountered species in our landscapes. Apple, ash, black gum, chestnut, elm, maple, and […]<\/p>\n","protected":false},"author":39,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[870,42,80,45,49,622],"tags":[488,60,63,1301,1302],"class_list":["post-16198","post","type-post","status-publish","format-standard","hentry","category-disease","category-forestry","category-trees","category-howto","category-plants","category-woodlands","tag-disease","tag-forestry","tag-how-to","tag-oak-tree","tag-tubakia","audience-for-enthusiasts","audience-for-homeowners","audience-for-landowners","audience-for-professionals"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t