{"id":22760,"date":"2023-06-08T08:30:19","date_gmt":"2023-06-08T12:30:19","guid":{"rendered":"https:\/\/www.purdue.edu\/fnr\/extension\/?p=22760"},"modified":"2025-08-06T09:08:46","modified_gmt":"2025-08-06T13:08:46","slug":"hemlock-woolly-adelgid-distribution-update","status":"publish","type":"post","link":"https:\/\/www.purdue.edu\/fnr\/extension\/hemlock-woolly-adelgid-distribution-update\/","title":{"rendered":"Hemlock Woolly Adelgid: Distribution Update"},"content":{"rendered":"
\"HWA<\/a>

Photo of the distribution of hemlock woolly adelgid in 2022.<\/p><\/div>\n

Purdue Landscape Report<\/a>: The hemlock woolly adelgid (Adelges tsugae<\/em>) continues its eastward spread across the US. In 2022, seven new counties were added to the distribution map of this invasive insect. While it is not present in Indiana yet, it is confirmed throughout the eastern USA from northern Georgia to Maine, extending west into Michigan, Ohio, and Kentucky.<\/p>\n

Since its introduction in the 1950s, hemlock woolly adelgid has caused severe mortality of eastern hemlock in the United States. Not only is this a significant impact on our native tree diversity, hemlock losses are linked to a decline in several native bird species in the New England and mid-Atlantic forests (Ellison et al. 2018). In Indiana, eastern hemlock has a scattered native range in isolated locations of the west-central and southern regions of the state. It typically grows on steep slopes, canyons, and ravines. Hemlock woolly adelgid is also a threat to ornamental hemlocks, which are frequently used in landscaping.<\/p>\n

<\/div>\n
\"forest<\/a>

Photo of forest in hills, forest mortality, hemlock woolly adelgid.<\/p><\/div>\n

\"hemlock<\/a>

Photo of needles from eastern hemlock.<\/p><\/div>\n

<\/div>\n

Identifying Eastern Hemlock
\n<\/strong>Hemlock woolly adelgid will only feed on hemlocks, so proper tree identification is crucial. If you\u2019re not sure whether your conifer is hemlock, check the color, shape, and arrangement of the needles. The needles of eastern hemlock grow singly (not in clusters) in alternate or opposite positions. The needles are flattened, and have two white stripes on the underside. The cones are small (1-2 cm), and when dry, they can resemble a rosette.<\/p>\n

Monitoring for Hemlock Woolly Adelgid
\n<\/strong>The white \u201cwool\u201d balls are the most tell-tale sign of this pest. Check the undersides of the branches at the base of the needles, and look for small, round, white cottony masses that cover the twig. These are actually the egg sacs of the hemlock woolly adelgid. You may also notice the \u201ccrawlers\u201d, or the mobile nymphs, which are tiny, oval-shaped, reddish-brown insects.<\/p>\n

<\/div>\n
\"crawler\"<\/a>

Photo of egg sacs of the hemlock woolly adelgid. These white \u201cwool\u201d balls are the most tell-tale sign of this pest.<\/p><\/div>\n

\"elongate<\/a>

Photo of elongate hemlock scale with flattened white spots.<\/p><\/div>\n

\n
\"signs\"<\/a>

Photo of hemlock wooly adelgids with egg sacks along the twig.<\/p><\/div>\n<\/div>\n

If you frequently check hemlock trees, you may see other white spots that resemble the woolly adelgid. The cocoons of elongate hemlock scale are often confused with hemlock woolly adelgid. However, note how the white \u201cspots\u201d from the scale infestation are flattened and cover the needles. Hemlock wooly adelgids congregate at the base of the needles along the twig, not on the needles themselves, and the egg sacs are round in shape. Single, large egg sacs found throughout the branch are often spider egg sacs or oak skeletonizer cocoons.<\/p>\n

Report any suspected findings of hemlock woolly adelgid at the Early Detection Distribution Map System (EDDMapS)<\/a> website.<\/p>\n

To view this original article and other Purdue Landscape Report articles, please visit Purdue Landscape Report<\/a>.<\/p>\n

Resources:
\n<\/strong>ID That Tree: Eastern Hemlock<\/a>, video, Purdue Extension \u2013 Forestry and Natural Resources (FNR) YouTube Channel
\n<\/strong>Distinguishing Hemlock From Yew<\/a>, The Purdue Landscape Report
\nNormal Needle Drop: Even Healthy Evergreens are not Evergreen<\/a>, Purdue Plant & Pest Diagnostic Lab (PPDL)
\nRecognizing and Managing Poison Hemlock<\/a>, Purdue Landscape Report
\nBe Careful Around Highly Toxic Poison Hemlock Plant This Summer<\/a>, Purdue Extension – FNR
\nPhomopsis Dieback of Spruce<\/a>, The Education Store, Purdue Extension resource center
\nChlorosis of Pine Trees<\/a>, The Purdue Landscape Report
\nBorers of Pines and Other Needle Bearing Evergreens in Landscapes<\/a>, The Education Store
\nStress-related Conifer Dieback<\/a>, The Education Store
\nCertified Soil Testing Laboratories<\/a>, Purdue Extension-Master Gardener Program
\nTree Installation: Process and Practices<\/a>, The Education Store
\nPlanting Your Tree Part 1: Choosing Your Tree, video<\/a>, Purdue Extension \u2013 FNR YouTube Channel
\nTree Defect Identification<\/a>, The Education Store
\nShrubs and Woody Vines of Indiana and the Midwest<\/a>, The Education Store
\nTree Risk Management<\/a>, The Education Store
\nConsumer Horticulture: Collecting Soil Samples for Testing<\/a>, The Education Store
\nFind an Arborist<\/a> website, Trees are Good, International Society of Arboriculture (ISA)
\nPurdue Pest and Plant Diagnostic Lab<\/a>, send in photo or samples<\/p>\n

Alicia Kelley<\/a>, Cooperative Agricultural Pest Survey (CAPS)<\/a> Coordinator
\nPurdue Extension – Entomology<\/p>\n","protected":false},"excerpt":{"rendered":"

Purdue Landscape Report: The hemlock woolly adelgid (Adelges tsugae) continues its eastward spread across the US. In 2022, seven new counties were added to the distribution map of this invasive insect. While it is not present in Indiana yet, it is confirmed throughout the eastern USA from northern Georgia to Maine, extending west into Michigan, […]<\/p>\n","protected":false},"author":58,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[38,42,80,49,54,622],"tags":[1792,131,1791,67,895,408],"class_list":["post-22760","post","type-post","status-publish","format-standard","hentry","category-alert","category-forestry","category-trees","category-plants","category-wildlife","category-woodlands","tag-distribution-update","tag-foresty","tag-hemlock-woolly-adelgid","tag-plants","tag-purdue-landscape-report","tag-trees","audience-for-enthusiasts","audience-for-homeowners","audience-for-landowners","audience-for-professionals"],"acf":[],"aioseo_notices":[],"publishpress_future_action":{"enabled":false,"date":"2026-04-23 03:35:17","action":"change-status","newStatus":"draft","terms":[],"taxonomy":"category","extraData":[]},"publishpress_future_workflow_manual_trigger":{"enabledWorkflows":[]},"_links":{"self":[{"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/posts\/22760","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\/58"}],"replies":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/comments?post=22760"}],"version-history":[{"count":24,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/posts\/22760\/revisions"}],"predecessor-version":[{"id":34370,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/posts\/22760\/revisions\/34370"}],"wp:attachment":[{"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/media?parent=22760"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/categories?post=22760"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.purdue.edu\/fnr\/extension\/wp-json\/wp\/v2\/tags?post=22760"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}