Who are these ferocious feeders that can decimate a lawn, destroy a rose bush or turn canna leaves into lace doilies almost overnight and where did they come from originally?
These iridescent copper and green beetles are Japanese beetles that overwinter as grubs in our lawns. They are native to Japan and first made their way to Riverton, N.J., in a shipment of iris in 1912 and then forged on to Yarmouth, N.S., in 1939.
Japanese beetles are now a gardening scourge from Ontario eastward. In their beetle stage, they attack the roots, foliage and fruit of more than 250 ornamental plants, trees, shrubs fruits and vegetable crops by skeletonizing the foliage, chomping on flower petals and munching on fruit. In their grub stage they feed on grass roots and turn once-healthy lawns into a brown, dead wasteland.
They love roses, cannas, zinnias, hops, birch and linden trees as well as raspberries, strawberries, blueberries, beans and the list goes on.
There are no natural predators in this country to help control these pests as there are in Japan. Even the birds won’t touch them.
So what to do? Several options are available to the home gardener although, sad to say, none are completely effective.
• Grow plants they don’t like (i.e. arborvitae, boxwood, begonia, dusty miller, pansies)
• Plant deterrent plants such as catnip, chives, tansy.
• Spray beetles with insecticidal soap.
• Pick them off by hand or shake them into a bucket of soapy water.
• Vacuum them up with a hand vacuum. But make sure that’s all you use that vacuum for!
• Although beetle traps are sold locally and they do attract and kill the beetles, many more miss the traps and stay around to feed on your plants another day so they are not the best route to go.
• Get them in the grub stage in early spring or early August by using beneficial nematodes. The nematodes won’t hurt your grass. They release a symbiotic material which eliminates the grubs in 72 hours then thousands more will be produced inside the host grub for the following generation. Check with your local nursery and follow package directions closely.
• For more info go to the Canadian Food Inspection Agency website (www.inspection.gc.ca).
Growing Green is a regular feature written by the Mount Hamilton Horticultural Society (gardenontario.org/site.php/mhhs). Helen MacPherson, the vice-president of the club, prepared this column.