{"id":16366,"date":"2025-07-16T10:16:48","date_gmt":"2025-07-16T15:16:48","guid":{"rendered":"https:\/\/uwm.edu\/field-station\/?p=16366"},"modified":"2025-07-16T10:16:51","modified_gmt":"2025-07-16T15:16:51","slug":"japanese-beetle-rerun","status":"publish","type":"post","link":"https:\/\/uwm.edu\/field-station\/bug-of-the-week\/japanese-beetle-rerun\/","title":{"rendered":"Japanese Beetle Rerun"},"content":{"rendered":"\n<p>Howdy, BugFans,<\/p>\n\n\n\n<p><strong>2025:\u00a0<\/strong>The BugLady has been prowling the landscape recently, both in wet areas and dry, and she\u2019s been seeing Japanese beetles or evidence of their feeding.\u00a0It used to be that their populations cycled between boom and not-boom, but the last few years all seem to deliver a fairly constant number of the beetles.\u00a0This slightly revised episode has some new words and pictures.<\/p>\n\n\n\n<p><strong>2009:&nbsp;<\/strong>For those of us of \u201ca certain age,\u201d (and before the notoriety of these new-fangled aliens like kudzu, zebra mussels, fire ants, and the emerald ash borer) the Japanese beetle will always be the poster child for Invasive Species.<\/p>\n\n\n\n<figure class=\"alignleft uwm-c-img--left\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetle17-6b-300x300.webp\" alt=\"Two Japanese beetles mating on a green leaf\" class=\"wp-image-16369\" srcset=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetle17-6b-300x300.webp 300w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetle17-6b-150x150.webp 150w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetle17-6b.webp 400w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<p>Their story is classic.\u00a0They arrived in New Jersey from Japan in 1912 hidden in a shipment of iris bulbs, but they weren\u2019t noticed until 1916. When Japanese beetles came to North America, they left their natural enemies at home.\u00a0In their first 8 years in the Land of the Free, and despite the control methods of the time, their range expanded to an astounding 2500 square miles.\u00a0They are presently well-established east of the Mississippi except Florida and are making inroads into the West via shipments of plants.\u00a0Like the mutants in horror movies, they just keep coming, despite the heavy fire power we lob at them (and in the case of the Japanese beetle, that includes imported pathogens, parasites, and predators).<\/p>\n\n\n\n<p>Like all successful invaders, they are generalists.\u00a0They have been recorded as eating some 300 species of plants (sources give numbers between 200 and 400).\u00a0Woody? Herbaceous?\u00a0Vine?\u00a0Flower?\u00a0Doesn\u2019t matter.\u00a0<\/p>\n\n\n\n<figure class=\"alignright uwm-c-img--right\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/beetle-japanese22-1rz-300x300.webp\" alt=\"Group of Japanese beetles feeding and mating on white blossoms\" class=\"wp-image-16370\" srcset=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/beetle-japanese22-1rz-300x300.webp 300w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/beetle-japanese22-1rz-150x150.webp 150w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/beetle-japanese22-1rz.webp 400w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<p>The Japanese beetle (<em>Popilla janponca<\/em>) is in the Scarab family, Scarabaeidae. If it weren\u2019t the\u00a0<em>Beetle from Hell<\/em>, we would admire its beauty and survival powers. It\u2019s a chunky half inch of beetle with a shiny green thorax and burnished bronze elytra (wing covers).\u00a0Five short, vertical, bright-white stripes of hair decorate the abdomen, and it sports two more white tufts like twin exhaust pipes.\u00a0It is diurnal (active during the day) and likes to feed in groups.<\/p>\n\n\n\n<p>The adults are primarily leaf skeletonizers, eating the soft tissue that lies between the tougher leaf veins, creating green lace (there\u00a0<em>are<\/em>\u00a0native leaf skeletonizers on the landscape, too). To the distress of gardeners, the adults\u2019 Top 50 menu choices includes roses and members of the rose family.\u00a0The larvae (grubs) feed underground on a variety of roots, especially those of horticultural and agricultural plants and turf grass (they\u2019re a pain at golf courses).\u00a0When they are working on a lawn in good numbers (1,500 grubs per square yard of sod have been recorded), the ground may feel a bit spongy underfoot.<\/p>\n\n\n\n<figure class=\"alignleft uwm-c-img--left\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetle20-1rz-300x300.webp\" alt=\"Single Japanese beetle on a leaf, showing metallic green and bronze colors\" class=\"wp-image-16371\" srcset=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetle20-1rz-300x300.webp 300w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetle20-1rz-150x150.webp 150w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetle20-1rz.webp 403w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<p>Mom lays her eggs in sod in mid-summer.\u00a0The kids hatch and spend the next 10 months as grubs.\u00a0They are full-grown when winter comes, and they overwinter as grubs in the soil, burrowing farther down as the frost line reaches deeper. They pupate in spring and emerge in mid-summer (they prefer warm, sunny, calm, moderately humid days). As the first Japanese beetles emerge and start to feed, they emit a scent \u2013 a pheromone \u2013 that attracts more and more adults. Females release a different pheromone to lure males.\u00a0During their two months as adults, they can wreak havoc.\u00a0<\/p>\n\n\n\n<figure class=\"alignright uwm-c-img--right\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/japanese-btle17-8rz-300x300.webp\" alt=\"Close-up of Japanese beetle with iridescent thorax and striped abdomen\" class=\"wp-image-16372\" srcset=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/japanese-btle17-8rz-300x300.webp 300w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/japanese-btle17-8rz-150x150.webp 150w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/japanese-btle17-8rz.webp 400w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<p>Some aggregations of beetles are initiated (inadvertently) by the food plant itself. Research suggests that a female Japanese beetle chews on a leaf, and the leaf gives off signature chemicals (OK \u2013 feeding-induced plant volatiles), and that instead of repelling the beetles, the scent attracts more beetles, both male and female, to feed (and, of course, while all those guys and gals are in the same neighborhood\u2026).<\/p>\n\n\n\n<figure class=\"alignleft uwm-c-img--left\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/japanese-btle17-9rz-300x300.webp\" alt=\"Two Japanese beetles feeding on a leaf with skeletonized damage\" class=\"wp-image-16373\" srcset=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/japanese-btle17-9rz-300x300.webp 300w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/japanese-btle17-9rz-150x150.webp 150w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/japanese-btle17-9rz.webp 400w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<p>The adults are eaten by starlings (another alien), and when there are large numbers of grubs in your lawn, moles, skunks, Canada geese and raccoons may make an appearance to excavate for them.\u00a0Biological controls that are being used include parasitic tachinid flies and tiphiid wasps (whose larvae go after \u2013 literally \u2013 the Japanese beetle larvae)<\/p>\n\n\n\n<figure class=\"alignright uwm-c-img--right\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetles18-10rz-300x300.webp\" alt=\"Line of Japanese beetles moving across a leaf\" class=\"wp-image-16374\" srcset=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetles18-10rz-300x300.webp 300w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetles18-10rz-150x150.webp 150w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/jap-beetles18-10rz.webp 400w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<p>And now, in the Don\u2019t-Put-Anything-in-Your-Ear-Smaller-Than-Your-Elbow category, a cautionary tale. A friend had a very Close Encounter with a Japanese beetle that flew into his ear while he was mowing the lawn (not normal behavior for Japanese beetles, as far as the BugLady knows).\u00a0This one\u2019s for you, Mike.\u00a0Instead of cutting its losses and backing out (perhaps Japanese beetles don\u2019t do \u201creverse\u201d), it burrowed farther in, grabbing the inside of Mike\u2019s ear canal with its bristly tarsi, heading for the eardrum and the gray matter beyond. Painful?\u00a0Oh, you betcha! The folks in the ER (who were, initially, skeptical\u00a0<em>because the beetle was so far down the ear canal that they could not actually\u00a0<\/em>see<em>\u00a0it<\/em>!) probably dined out on\u00a0<em>that<\/em>\u00a0story for months.<\/p>\n\n\n\n<figure class=\"alignleft uwm-c-img--left\"><img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/beetle-japanese22-2rz-300x300.webp\" alt=\"Pair of Japanese beetles feeding on a curled leaf edge\" class=\"wp-image-16375\" srcset=\"https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/beetle-japanese22-2rz-300x300.webp 300w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/beetle-japanese22-2rz-150x150.webp 150w, https:\/\/uwm.edu\/field-station\/wp-content\/uploads\/sites\/380\/2025\/07\/beetle-japanese22-2rz.webp 400w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<p>Just when you thought it was safe\u2026.&nbsp;<\/p>\n\n\n\n<p>But they really are a spiffy-looking beetle.<\/p>\n\n\n\n<p><em>The BugLady<\/em><\/p>\n\n\n<div class=\"taxonomy-post_tag wp-block-post-terms\"><a href=\"https:\/\/uwm.edu\/field-station\/tag\/beetles\/\" rel=\"tag\">Beetles<\/a><span class=\"wp-block-post-terms__separator\">, <\/span><a href=\"https:\/\/uwm.edu\/field-station\/tag\/invasive-species\/\" rel=\"tag\">Invasive species<\/a><span class=\"wp-block-post-terms__separator\">, <\/span><a href=\"https:\/\/uwm.edu\/field-station\/tag\/japanese-bettles\/\" rel=\"tag\">Japanese Bettles<\/a><span class=\"wp-block-post-terms__separator\">, <\/span><a href=\"https:\/\/uwm.edu\/field-station\/tag\/mating-beetles\/\" rel=\"tag\">Mating beetles<\/a><span class=\"wp-block-post-terms__separator\">, <\/span><a href=\"https:\/\/uwm.edu\/field-station\/tag\/popillia-japonica\/\" rel=\"tag\">Popillia japonica<\/a><\/div>","protected":false},"excerpt":{"rendered":"<p>Howdy, BugFans, 2025:\u00a0The BugLady has been prowling the landscape recently, both in wet areas and dry, and she\u2019s been seeing Japanese beetles or evidence of their feeding.\u00a0It used to be that their populations cycled between boom and not-boom, but the &hellip;<\/p>\n","protected":false},"author":38860,"featured_media":16368,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":"","uwm_wg_additional_authors":[]},"categories":[8],"tags":[30,942,940,943,941],"class_list":["post-16366","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-bug-of-the-week","tag-beetles","tag-invasive-species","tag-japanese-bettles","tag-mating-beetles","tag-popillia-japonica"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.3 (Yoast SEO v27.3) - 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