{"id":611972317510,"date":"2025-10-16T16:41:48","date_gmt":"2025-10-16T16:41:48","guid":{"rendered":"https:\/\/blogs.ashridgetrees.co.uk\/blogs\/uncategorized\/horse-chestnut-leaf-blotch\/"},"modified":"2026-04-21T08:41:16","modified_gmt":"2026-04-21T08:41:16","slug":"horse-chestnut-leaf-blotch","status":"publish","type":"post","link":"https:\/\/blogs.ashridgetrees.co.uk\/blogs\/trees\/horse-chestnut-leaf-blotch\/","title":{"rendered":"Horse Chestnut Leaf Blotch"},"content":{"rendered":"<h3>What are these brown spots on my conker tree\u2019s leaves?<\/h3><p><strong>Horse Chestnut Leaf Blotch<\/strong> is a fungal condition called <em>Guignardia aesculi <\/em>that affects <a href=\"https:\/\/www.ashridgetrees.co.uk\/collections\/chestnut-trees-conker-sweet\">horse chestnuts<\/a>, not <a href=\"https:\/\/www.ashridgetrees.co.uk\/products\/sweet-chestnut-trees-castanea-sativa\">sweet chestnut<\/a>.<\/p><p><img decoding=\"async\" src=\"https:\/\/blogs.ashridgetrees.co.uk\/wp-content\/uploads\/2026\/04\/chestnut-leaf-blotch.webp\" alt=\"Chestnut leaf blotch\"><\/p><p>The main symptom is irregular brown blotches on the leaves, starting at the edges, from late June. <\/p><ul>\n<li>Unlike leaf miner damage, these blotches are chestnut brown and tend to be irregular and rounded.<\/li>\n<li>Leaf miners tend to burrow between two veins, making bands of damage that are lighter in colour. <\/li>\n<li>By the middle of September, the two conditions look very similar, and the end result of early de-foliation is the same. <\/li>\n<\/ul><p>Although Horse Chestnut leaf blotch is not pretty, it does not significantly affect the strength or health of the infected tree, unlike <a href=\"https:\/\/www.ashridgetrees.co.uk\/blogs\/trees\/horse-chestnut-tree-canker-disease\">Bleeding Canker<\/a>.<\/p><h3>Horse Chestnut Leaf Blotch Treatment<\/h3><p>The fungal spores overwinter in fallen leaves, rising again into the trees in spring. <\/p><p>Therefore, the only realistic control-prevention is to break the cycle by raking up and burning or binning the fallen leaves.<\/p><p>There are no fungicides on the market for Horse Chestnut Leaf Blotch, and in any case spraying a mature tree is not realistic.<\/p>\n\n<section class=\"prodshow-shopify-block\" \n         id=\"prodshow-block-1\"\n         >\n\t\n\t<div class=\"prodshow-container\">\n\t\t\n\t\t\t\t\t<!-- Multiple Products\/Collection View -->\n\t\t\t<div class=\"prodshow-header\">\n\t\t\t\t<div>\n\t\t\t\t\t\t\t\t\t\t\t<h2 class=\"prodshow-title\">\n\t\t\t\t\t\t\tRelated Products\t\t\t\t\t\t<\/h2>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\t\t\t<\/div>\n\n\t\t\t<div class=\"prodshow-carousel\" data-carousel=\"prodshow-block-1\">\n\t\t\t\t<div class=\"prodshow-carousel-viewport\">\n\t\t\t\t\t<div class=\"prodshow-carousel-container\">\n\t\t\t\t\t\t<div class=\"prodshow-product-card\">\n\t<a 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Horse Chestnut Leaf Blotch is a fungal condition called Guignardia aesculi that&hellip;<\/p>\n","protected":false},"author":2,"featured_media":613787866198,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[59,69],"class_list":["post-611972317510","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-trees","tag-gardening-tips-plant-pests-and-diseases","tag-horse-chestnut"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.6 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Horse Chestnut Leaf Blotch \u2013 Brown Spots on Conker Trees<\/title>\n<meta name=\"description\" content=\"Brown blotches on horse chestnut leaves from late June? This fungal condition Guignardia aesculi causes irregular brown spots but won&#039;t harm your tree&#039;s health.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.ashridgetrees.co.uk\/blogs\/trees\/horse-chestnut-leaf-blotch\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Horse Chestnut Leaf Blotch \u2013 Brown Spots on Conker Trees\" \/>\n<meta property=\"og:description\" content=\"Brown blotches on horse chestnut leaves from late June? This fungal condition Guignardia aesculi causes irregular brown spots but won&#039;t harm your tree&#039;s health.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/blogs.ashridgetrees.co.uk\/blogs\/trees\/horse-chestnut-leaf-blotch\/\" \/>\n<meta property=\"og:site_name\" content=\"Ashridge Blog\" \/>\n<meta property=\"article:published_time\" content=\"2025-10-16T16:41:48+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-04-21T08:41:16+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/blogs.ashridgetrees.co.uk\/wp-content\/uploads\/2026\/04\/chestnut-leaf-blotch-2.webp\" \/>\n\t<meta property=\"og:image:width\" content=\"600\" \/>\n\t<meta property=\"og:image:height\" content=\"600\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Julian de Bosdari\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Julian de Bosdari\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/\"},\"author\":{\"name\":\"Julian de Bosdari\",\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/#\\\/schema\\\/person\\\/3e3504b4d1b099fc7a8ad8d78db399b4\"},\"headline\":\"Horse Chestnut Leaf Blotch\",\"datePublished\":\"2025-10-16T16:41:48+00:00\",\"dateModified\":\"2026-04-21T08:41:16+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/\"},\"wordCount\":190,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/#organization\"},\"image\":{\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/wp-content\\\/uploads\\\/2026\\\/04\\\/chestnut-leaf-blotch-2.webp\",\"keywords\":[\"Gardening Tips&gt;Plant Pests &amp; Diseases\",\"Horse chestnut\"],\"articleSection\":[\"Trees\"],\"inLanguage\":\"en-GB\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/\",\"url\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/\",\"name\":\"Horse Chestnut Leaf Blotch \u2013 Brown Spots on Conker Trees\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/blogs\\\/trees\\\/horse-chestnut-leaf-blotch\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/blogs.ashridgetrees.co.uk\\\/wp-content\\\/uploads\\\/2026\\\/04\\\/chestnut-leaf-blotch-2.webp\",\"datePublished\":\"2025-10-16T16:41:48+00:00\",\"dateModified\":\"2026-04-21T08:41:16+00:00\",\"description\":\"Brown blotches on horse chestnut leaves from late June? 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