Thursday, July 12, 2012

Japanese Beetle - Popillia japonica

The Japanese Beetle
One of the most destructive beetles has come out of hiding (pupated). The ever multiplying Japanese Beetle is invading the garden once again. Like most bugs this year, their populations are quite numerous for this time in July.

I really shouldn't complain about them. I pretty much have a job because of pesky bugs and weeds. Although, seeing their skeletonized aftermath, there's nothing but frustration brewing under the collar. I can't help but wonder what our gardens would look like if the Japanese Beetle never made the journey over the ocean ages ago.

Photo Source: Kentucky College of Agriculture
The only way we can control them properly, is to know their life cycle. Kentucky's College of Agriculture has this fantastic beetle life cycle diagram. Once you've seen them in the garden, you know how they populate quickly. Usually I find them in pairs, if not in masses - reproducing in action. :) At least that's one good thing, you can collect them rather easily.

In late July and early August, the hotter the weather the more they congregate on the top of plants - near blossoms or tender leaves.They start at the top, working their way down the plant. A group of beetles attracts more beetles. Once, I counted at least 20 beetles on one unfurling rose.The beetles are most active during the hottest part of the day (noon-to-three).
Eating Parthenocissus quinquefolia - Virginia Creeper

One of the reason's they are so rampant, is because of North America's love for turf. They overwinter as grubs in turf. When roses, fruit trees and other food interests are closest to turf, the more they get attacked by the beetles.


Congregating on top of vine
1) Collect as many of the beetles first thing in the morning. They are sort of "slow" in cooler weather. Sluggish and not flying away when you collect them. However, they may not be seen as readily. They are the most active during the heat of the day, so you may have more success in finding them. Squishing them between your fingers is best.Collecting is quite effective if you are persistent and thorough. Doing so prevents them from laying eggs in turf close by. I usually clap my hands quite harshly right over the grouping of beetles. The smash stuns them and they generally die as a result. It's hard to collect dozens in one spot. Some fly away and come back.
The beetles make dozens of holes, until most of the leaf is gone.

2) Japanese Beetle Traps:  There are different kinds on the market. Some are pheromones mimicking females - attracting males and others attract the beetles with a food source. Both are quite effective. As when two or more beetles are gathered, more come round.  Sometimes, unfortunately - the traps attract more Japanese Beetles to your garden from the neighbourhood than before. It's best to place the traps downwind at the furthest direction away from the path of highly edible plants that the beetles love. In my experience, walking slowly by your roses or infested plants with the Japanese Beetle trap, will encourage them to follow you. As I was hanging the last trap I placed, about 5 beetles gathered at the top of the trap before I even fully secured it. It works.
Breeding machines!

Another control is planting material that isn't attractive to the Japanese Beetle. Know the plants that Japanese Beetles devour: Here are 2 comprehensive lists

Be persistent and look for the typical hole markings they leave behind.

Best of luck!


  1. Ack!! Yes, I also have these horrible critters! and they're devouring my virginia creeper! I have been spraying them with soapy water, but will do the morning thing and try to collect them and MURDER them :D thanks for the info!

  2. I have roses for the first time and they got over them. They destroyed a particular hosta I have in several spots around my house, but ignored the other kinds. I don't know the name of the destroyed one, but my raspberry sundae hosta were untouched.

    1. They are such a pest, aren't they!?Try collecting as many as you can! Hope we have a deep freeze this winter to help reduce their numbers!


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