The tiresome Japanese beetle has been busy doing its thing again, tormenting gardeners. The first time I encountered them in my garden I tried to look upon the Boston ivy as a greenish lace curtain draped over the fence. It didn’t work. There was no avoiding the realization that the leaves had been shredded by Japanese beetles.
Last year it was the hazel and by the time I noticed it was
too late and the poor tree suffered the same treatment. There were just too
many to deal with, and besides, they were out of reach. Other times these shiny
brown and green beetles with locust-like appetites have appeared on my roses
where at least they’re easy to spot and it’s easy to shake them off into a pail
of soapy water. That’s about the most effective way to dispatch them. Sadly,
for some gardeners, so many show up to feast they’d need to set up a dishwasher
in the back yard and herd them in. So far this year I’ve only seen two and used
the quick and simple squishing technique — ugh.
It’s at the grub stage in lawns where some control can be
achieved by an application of nematodes, but to be effective, correct time of
application, weather, and specific soil temperature must all coincide. Even
then, it’s of little help if yours is the only lawn in the area to be treated.
You might be wondering why these voracious pests haven’t defoliated their homeland by now. In Japan they’re seen only as a minor pest, simply because of a difference in gardening culture. The country isn’t blanketed with lawns the way North America is, and that means far fewer places accommodate the lifecycle of the grubs.
There are traps available to limit damage, and they work extremely well, or sort of. They attract the beetles with two types of baits or pheromones, a sex one to attract the males and a flowery one to tempt both male and female. The drawback is they can attract thousands of beetles and as they pass over your garden on their incoming flight path, enough of them will stop off for a quick feed and anything else they might have in mind. No harm in trying with traps. Better still, convince all your neighbours to install a few.
The most effective solution, though not the easiest, is to gradually replace any plants and trees that the beetles are attracted to, and there are over 300 species. There are even more that they’ll never bother, and if that’s the route you choose to take, a quick search online will provide lists of both.
more possible way to limit the damage the beetles do, is to plant geraniums, lots of them. Research by a couple of scientists confirmed anecdotal reports that geraniums (pelargoniums) are toxic to these pests. After feeding on the flowers, the study showed the beetles became paralysed for up to 16 hours, however, it didn’t finish them off. When they recovered, they went back for more. Made them easier to pick off, I suppose, but it might take a lawn full of geraniums to provide any relief. Other anecdotal reports suggested the same effect occurred when beetles fed on flowers of bottlebrush buckeye (Aesculus parviflora), but when tested, no adverse effects were observed.
Nature does have a way of challenging us, so for now it looks like I’ll continue picking and squishing, at least until balance is restored.