Elizabeth Exstrom: Japanese bugs are tiny horrors | Home & Garden

They are baaaaccck!! That’s right, the Japanese Beetles are back.

What Exactly is a Japanese Beetle and Why Should We Worry? Knowing a little about these tiny horrors will help ensure your landscape doesn’t become their next meal.

This beetle is related to other common pests that we see. The Japanese beetle is related to the May/June beetle and the masked beetle. All take the immature form of a caterpillar, which can damage the turf and roots of landscape plants. The adult form of this insect is slightly prettier than its cousins. While the May/June Beetle and Masked Beetle are both brown, the Japanese Beetle is a colorful combination of iridescent green head and thorax and copper-colored wings.







Elizabeth Exstrom


Japanese beetles, as the name suggests, are not native to Nebraska. They are native to Japan and were stowaways in a shipment that made its way to North America. With no natural predators, disease, or competition, the Japanese beetle has been able to establish itself in the States.

The Japanese beetle has more than just a pretty face, it has a dark side. Unlike its cousins, which only deal damage in larval form, the Japanese Beetle adults can also deal damage. As an adult, it feeds on over 300 different species of plants, including roses, lime trees, soybeans, grapes, and more.

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The adult has sharp chewing mouthparts and uses them to eat leaves, flowers, and fruit. Leaf tissue is skeletonized, leaving only the vascular parts of the leaf in a doily-like pattern. Flowers appear finely shredded as if blasted with sand and fruits are chewed and hollowed out. As immature larvae, these insects are lawn pests, causing damage to lawns, sports fields, and golf courses. They feed on peat roots and turn lawns brown and curl up like a carpet.

The adult Japanese beetles are fairly predictable. They emerge and begin feeding on plants in June and July. During daylight hours, adults often feed in clusters on host plants. Adult activity is most intense for a period of about four to six weeks. During this time, the adult females lay eggs in the soil, which turn into turf-damaging caterpillars. The grubs actively feed during the summer months and usually reach their full size in August or September. They overwinter as caterpillars and feed again in spring before emerging as adults to start the cycle over.

Control for these little guys can be difficult. If you only have a few, you can pluck the bugs from plants and place them in soapy water to kill them, or place a fine-mesh net over plants like roses. Two organic sprays, neem and pyola, can protect plants, but usually for no more than three to seven days.

Adults can be chemically controlled with pyrethroid products such as Tempo and Bayer Advanced Lawn & Garden Multi-Insect Killer (cyfluthrin) or Ortho Bug B Gone (bifenthrin). Sevin (Carbaryl) is another option. These all offer protection for foliage and flowers for about two weeks after a thorough treatment.

Since some of these insecticides can also affect pollinators, try to only spray in the evening and after the bugs have cleared the flowers. Be sure to follow label directions specifically to avoid harming pollinators.

Pass on the Japanese bug traps that can be found in the big department stores. They do an excellent job of catching any bugs you may have, but they also attract bugs from around the neighborhood.

If grubs become a problem, insecticides applied at the right time of year can be very helpful in controlling them. GrubEx (chlorantraniliprole), applied mid-June to mid-July, can eliminate populations of young maggots.

With a little scouting, you can now be prepared for the Japanese bug invasion. Keep your eyes open and your roses covered and all will pass in time.

Elizabeth Exstrom is the Horticultural Extension Instructor at Nebraska Extension in Hall County. Contact them at 308-385-5088 or ekillinger2@unl.edu. Follow her blog at http://huskerhort.com or visit HuskerHort on Facebook and Twitter.

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