In about four or five weeks many areas of Ontario, Eastern Canada and a good part of the United States will be experiencing a type of beetlemania. However, this non-musical invasion doesn’t originate from Liverpool, has never appeared on the Ed Sullivan show, and any screams and shrieking will probably come from someone unlucky enough to have one of these pesky pests land in their hair while walking by an infested garden or park.
The cause of this summer mayhem are magical mystery bugs called Japanese beetles (Popilla japonica), an alien pest which is one of the few members of the order Coleoptera that cause severe plant damage in both their larval and adult stages. They first appeared on North American soil in 1916 in New Jersey and sneaked across the border to Nova Scotia during the late 30s, probably in an infested soil or plant shipment.
Since then, the destructive little beasts have been chewing their way west from Newfoundland to Ontario. Ironically, they don’t appear to be a serious problem in Western areas of the country, closer to their ancestral homeland of Japan – probably due to strict agricultural import regulations.
I saw plenty of them around the Beach last year. In Scarborough and northern parts of the city they have become epidemic from the beginning of July to the middle of September. Last year a 27-acre North York garden park set out monitoring traps and ended up capturing over 20,000 of the insects every day during their peak feeding and mating frenzy in early August.
Japanese beetles are hard to miss when they are active – even underground. As the soil warms through late spring and early summer, larvae chow down on grass roots, leaving a swath of brown deadened turf in their wake (quickly rolled up by raccoons and skunks looking for a nocturnal shrimp cocktail). After emerging from the pupae, 12 mm adults with attractive copper coloured wings and emerald heads fly from the soil and immediately release a ‘congregational’ pheromone that signals others to ‘come and get it’. And come they do, using a highly developed olfactory sense to clumsily fly about like bumper cars until they zero in on a floral or hormonal scent that guides them to a food source, where they gather to mate and cause horticultural havoc by rapidly skeletonizing foliage and destroying blooms.
Of the more than 300 plants on their grocery list, rose buds and blossoms are by far their favourite, although they will feast on corkscrew hazel, rose of Sharon, peach and cherry trees, grapevines and most types of maples, including Japanese and harlequin varieties. Surprisingly, they are one of the rare insects that will gorge themselves on the leaves of poison ivy if they happen to bump into the plant – so I suppose I can grudgingly award them one point for that!
Control of the little critters is difficult but not impossible, especially in small marginally infested areas. Milky spore disease is a harmless organic bacterium that can be applied to warm soil in August. The powdery substance specifically targets the larvae of Japanese beetles and may take a couple of years to show an effect, but when it does become established the spores will continue to work for decades.
For control of adult beetles, there has always been a heated debate about the merits of using pheromone traps. They do capture huge numbers of the bugs, but these devices are most useful for monitoring purposes, and to divert the insects away from valuable plant assets on large properties where established populations already exist. In small gardens the traps may just invite passing squadrons to chow down at your place instead of somebody else’s rose garden.
A few years ago I tried an unconventional deterrent while trying to protect hybrid tea roses. I had heard that when Japanese beetles feed on the leaves of annual geraniums they are stunned into a sort of drunken stupor that causes them to fall to the ground, making them easy pickings for predators. I painstakingly planted a dense geranium border around the garden and to my surprise they did appear to be less active and incapacitated after nibbling on the foliage. Unfortunately there are very few bird predators that find their hard shell palatable, and 24 hours later the bugs simply shook off their hangovers and continued on with their destructive ways.
I suppose short of feeding them geraniums and sweeping up drunk beetles, the best advice I can offer is keep your eyes peeled for the bugs when they appear and follow a regular routine of hand brushing the beetles into a bucket of soapy water during the early morning when they are less active. Milky spore and beneficial nematodes will help with the battle, and if we are lucky, the cold winter and extended period of frozen ground may have stopped them in their tracks, or at least delayed their arrival.
Steven Chadwick is a professional gardener and horticulturist, and longtime Beach resident
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