Gardening Harmful animals Lawn Plant pests

Coping with Rose Chafers

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Rose chafer

The American rose chafer* (Macrodactylus subspinosus) is slender pale green to tan beetle with long orange legs. Although it is native to North America, its distribution is fairly irregular: you may have a major problem with it while a neighbor just down the road has never even seen it. It can be found anywhere east of the Rockies.

*The European rose chafer or green rose chafer (Cetonia aurata), metallic green in color, is a different species and is not found in North America.
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Rose chafers on a rose flower.

Where it is present, the rose chafer can cause a lot of damage, devouring the leaves and flowers of roses. It may eat flowers entirely, while it can skeletonize foliage, leaving only the veins. Moreover, in spite of its name, the rose chafer is far from limited to roses, and will readily consume many other plants, including ivies, Japanese lilacs, hydrangeas, mountain ashes, Boston ivy, daisies, grapes, spireas, elderberries, peonies (flowers), brambles, cabbages, strawberries, apples, hollyhocks, cinquefoils, irises, elms, oaks, birches and hawthorns.

Stop Gap Measures

It is pretty much impossible to entirely eliminate  chafers while the adults are already feeding on your plants, which will be in from late May to mid-July in most regions. The best you can expect is to reduce their numbers to the point where they cause little damage.

Probably the easiest way of controlling the adults is to knock them off the plant into a pail of soapy water or to suck them up with a handheld vacuum (then dump the prisoners into soapy water). For best results, do this in the morning when they are less active.

There are also traps designed specifically for rose chafers that give off a pheromone that attracts them. I have never seen these traps in stores, but you can obtain them from organic insect control specialists, like Nic Natural Insect Control. It is important to place these traps at least 30 feet (9 m) away from any plants the adults like to feed on, perhaps in the middle of a vast lawn or in a parking lot, because while they readily attract chafers into the vicinity of the trap, only a minority of them actually enter it. Then any chafers not caught will damage nearby plants that suit their diet.

Long-term Control

For long-term control, you have to work on either reducing the chafer’s egg-laying ability or on reducing the number of larvae.

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Rose chafers prefer to lay their eggs in lawns on sandy soil.

Rose chafers prefer to lay their eggs in sandy soil, preferably in dry, sunny spots covered in grass or weeds, especially lawns. They lay less abundantly in lawns that contain a significant proportion of clover. They dislike and will usually avoid rich, moist soils and shady spots.

To discourage them, you might want to redo your lawn by covering it with a good 6 inches (15 cm) of quality sand-free topsoil, then resowing with a mixture of lawn grasses and clover. Or grow a clover lawn. You can also try planting shrubs, trees, and tall perennials to shade the soil. Obviously, it would help if all your neighbors did the same, as the adults do fly, although they rarely travel far.

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Rose chafer grubs look much like other white grubs.

The larval stage of the beetle is a white C-shaped grub that lives in the soil. It is hard to distinguish from the grubs of Japanese beetles or May beetles (June beetles), which also live in lawns under much the same conditions. Nematodes designed to control white grubs will help control all types of white grub, including those of the rose chafer. Beneficial nematodes are readily available in most garden centers or can be ordered from various organic insect control specialists.

There is only one generation of rose chafer per year. After 3 to 6 weeks of damage, the infestation will end as suddenly as it began. Usually affected plants quickly recuperate, producing new leaves, and soon you can no longer see the damage. However, by then the chafers may have already ruined that summer’s blooms or fruit.

Curiously, rose chafers are said to be toxic to chickens, so you might want to keep your hens locked up when they are present!

No Host Plants, No Problem!

The most laidback way to control rose chafer? Every year, eliminate the 3 or 4 plants most seriously attacked, replacing them with species that are not affected (you’ll see which ones in your garden). In just a few years, your yard will no longer offer rose chafers anything interesting and they’ll go elsewhere!20160702A

 

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

5 comments on “Coping with Rose Chafers

  1. Pingback: The Enemy Returns: Rose Chafer Beetles – Box & Bay

  2. Russell Rolffs

    Thanks for article. On what basis do you say that they do not prefer clover lawns? I have read elsewhere that they prefer clover, and I am looking for a cover crop mixture to deter chafers. Thanks.

    • I didn’t really explain that well. The grubs feed mostly on grass roots and lawns with clover are considered unattractive places for egg laying. However, adults freely feed on clover leaves.

  3. Russell Rolffs

    Thanks for the write-up. I am seeing conflicting info on clover and Rose chafers. What is your source of info that they don’t prefer clover sod/roots?

    • I may have been wrong about this, but don’t have time to do a thorough search at this time. I’m sending you this message, because I’m afraid if I pull the blog immediately, you won’t get the message. On Sunday, I’ll take the blog down, at least temporarily, until I can check this out.

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