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Japanese Beetles

posted Jul 14, 2013, 2:56 PM by James Roe   [ updated Jul 14, 2013, 2:57 PM ]
As mentioned elsewhere last year was my first year to get back into gardening after a long hiatus.  We had a terrible drought and heatwave, groundhogs, rats and - Japanese Beetles with which I had no previous experience.  They attacked my new Knockout Roses in such numbers that I thought I should spray - which I did.  The beetles that were hit by the spray appeared to die quickly but the next day there were more.  This isn't working too well I decided so I went to town and bought some Japanese Beetle traps.  They use a sex attractant to lure the bugs into a plastic bag.  The instructions said to put the bag at least 30 feet away from where you wouldn't want more beetles.  So I did.

Yvonne and I went to town to run some errands and when we came back two hours later she said, "look, the wind has knocked down your trap and it has broken one of your Elephant Ear leaves."  I went out to check and found the the wind hadn't knocked the trap down, it had fallen of the weight of a bag full of  beetles.  The beetles that couldn't get into the bag had eaten my Elephant Ear leaf. :(  I emptied the bag, replaced it and put another trap out by the garden.  As I was walking out to place the trap the sex-starved Japanese Beetles were dive bombing my head!  I put out another couple of traps with the same heavy usage.  I figure I emptied the better part of a bushel of dead beetles.

I figured this sex attractant was so  powerful that it attracted bugs from the entire county and that beetle traps are NOT a good idea.

Fast forward to this year.  When a few Japanese Beetles started appearing on my Knockout Roses I resolved to pick them off and eschew the traps.  I put about 1/2 inch of water in the bottom of an old jelly jar with a drop of dishwashing detergent for good measure.  I then set about knocking the beetles (sometimes three at a time ) into the jar.  It needed to be repeated at least twice a day and I would get dozens each time.  Not the most fun but I relished the thought that none of those beetles would lay eggs that would plague me next year.  Stanley Dillon of the Green Thumber radio show says that each adult beetle lays about 50 eggs for the next generation.

Then it hit me.  The infestation this year (so far) hasn't been really heavy.  Those tens of thousands of beetles I killed last year did not lay any eggs either.  Maybe the traps were a good idea?  Makes sense.  So I installed a trap out on the southern edge of my yard and, so far, it has captured a mere hundred or so beetles.  Maybe I did decimate their numbers last year?  My place has been vacant many years with little or no attention to the landscape or grounds so maybe it was a hot bed of Japanese Beetles that have been dealt a severe blow.  I hope so.

As another defense against the beetles I spread milky spore disease  around my flower and garden beds last summer.  This disease attacks and kills the grubs in the ground.  When the grubs die, more of the milky spore infects the ground to make it even more effective.  I think I am on the right path to controlling these bugs.  I'm still patrolling the rose bushes with my jelly jar but maybe next year I won't see any?