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Japanese Beetles

In reading post after post on this subject I'm just amazed at how all but two writers have noted how important it is to understand the life cycle of this insect.  Without understanding it's cycle, how many broods you may have in your area of the country and what is the best time for control...you seem to be doomed until nature takes it's course.  Part of a good IPM program involves understanding the target and monitoring the target.  There are threshold levels for JB grubs that are acceptable and levels that indicate that treatment and or a plan is needed.
 
For those who have tried pyrethrin and have had little to no success...remember that this botanical insecticide degrades very rapidly in sunlight.  If you use it late in the day or early in the morning you will have much greater success.  Also, use pyrethrin that has PPB in it.  That's piperonyl butoxide.  This is synergist that increases and enhances the effect of the pyrethrin.  Note though that if you are running a strictly organic operation PPB is not considered organic.  Most, but not all commercial formulations of pyrethrin such as Shultz's Expert line do contain PPB.  However, if you buy a pyrethrin concentrate instead of the RTU (ready to use) formulations the percentage of PPB is usually higher and the product much more effective.
 
I much prefer this to using cabaryl (Sevin) which is much more controversial, non selective, extremely toxic to honey bees and butterflies...to name just a few of the non target insects it will kill.
 
If you use traps...be aware of your prevailing winds.  As noted in other posts if traps are placed improperly they can do much more harm than good.
 
And for those who choose the picking method...on female that is missed will lay up to 200 eggs.
 
Here's a thought though.  Consider using a small portable vacuum such as a Dust Buster to collect these wonderful critters.
 
There is a map available, possibly from USDA that shows the annual spread and severity of infestation of the JB.  Of course I can't remember where I saw it but it was in the last year.
 
There are also two other beetles that gardeners often confuse with Japanese Beetles.  These are the Oriental beetle and the Asiatic beetle.
 
Sorry for the rant but when horticulture is your passion....
 

Andrew Messinger
The Hampton Gardener
The Hampton Gardener is a Registered Trade Mark
(Published every Thursday in the Southampton Press)



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