{"id":10023,"date":"2020-01-13T11:52:09","date_gmt":"2020-01-13T16:52:09","guid":{"rendered":"https:\/\/extension.umaine.edu\/home-and-garden-ipm\/?page_id=10023"},"modified":"2025-08-26T12:36:12","modified_gmt":"2025-08-26T16:36:12","slug":"locust-borer","status":"publish","type":"page","link":"https:\/\/extension.umaine.edu\/home-and-garden-ipm\/fact-sheets\/common-name-listing\/locust-borer\/","title":{"rendered":"Locust Borer"},"content":{"rendered":"

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Dave Thompson<\/span>Locust Borer (Megacyllene robiniae<\/i>) (Hollis, ME; 8\/26\/2025) (Photo courtesy of Dave Thompson)<\/figcaption><\/figure>\n

The Locust Borer <\/strong>(Megacyllene robiniae<\/i>) is a species of long-horned beetle (Family Cerambycidae).<\/em> Adults are about one-inch long with reddish legs, and feed a little on the pollen and nectar of goldenrod plants, upon which they are well camouflaged courtesy of the yellow and black bars they possess on their head, pronotum, and elytra (there is a distinctive “W” mark across their elytra\/wing coverings). The black and yellow markings also bestow a fair amount of resemblance to a wasp or hornet, which likely affords them some protection from certain predators. There are two closely-related species: M. caryae<\/i> and M. decora<\/i>.\u00a0 M. caryae<\/em> is known as the Painted Hickory Borer. The Sugar Maple Borer, Glycobius speciosus, <\/i>is another species that has very similar coloring and markings so it’s important to recognize the differences amongst them (see links below)<\/em>.<\/p>\n

Locust borer larvae are white and legless with a large prothorax, typical of long-horned beetle larvae.\u00a0 The larval hosts of the Megacyllene<\/i> genus seem to be restricted to plants in the Fabaceae family, commonly known as the legume, pea, or bean family<\/span>.\u00a0 Megacyllene robiniae<\/i> (in its larval stage), is a serious pest of Robinia pseudoacacia<\/i>, the black locust tree. The larvae damage the trees by creating numerous large tunnels in the branches while feeding on the sapwood.\u00a0 These tunnels can eventually cause the branches to crack or break off, and they also disrupt the flow of nutrients and water within the tree, thereby inhibiting new growth. The tunnels also serve as infection sites for fungal spores, such as those belonging to the fungus, Phellinus robiniae, <\/i>which causes a damaging heart rot disease in locust trees.\u00a0 Larvae of M. caryae<\/i> attack hickory, black walnut, butternut, osage orange, and mulberry.<\/p>\n

Life Cycle:<\/strong> There is one generation per year. Eggs are laid singly in the fall inside deep pits within the bark which the female beetle carves out for the purpose. Eggs hatch in the spring and the larvae feed throughout the spring and summer with pupation occurring mostly in August. Adults begin to emerge during late August and throughout September.<\/p>\n\n