I've been using this hack for the last two years and have had great results.
What makes a Japanese Beetle trap better than using an insecticide? The trap uses a sexual attractant rather than a chemical which is bad for the environment and bad for you, too.
Also, there is the argument that by using an attractant you will lure beetles from other yards into your yard. My thought on this is that all Japanese Beetles are bad and as long as they go into the trap (and they will) who cares whence they came.
A Japanese beetles lives between 30 to 45 days. Females feed, mate, and lay between 1 and 5 eggs. Then they repeat this process every 24 to 48 hours until their life span is completed. So you can see that if you do nothing the beetles will multiply exponentially.
I was late putting out traps the first year. The second year I put the traps out as soon as I saw a few beetles. But this year I am putting out the traps before I see any beetles.
The University of Minnesota Extension
According to the above chart I better get my traps ready pronto. We usually start seeing them around July 4th but I want to trap as many as possible so I need to be ready.
Japanese Beetles defoliate trees when they are beetles and eat the roots of your grass when they are in the grub phase. So they are doing damage even when you can't see them.
How do I know if I am actually decreasing the population of Japanese Beetles in my yard? First of all, whenever I dig in the soil I look for grubs. Every shovel full of soil revealed multiple grubs when we first purchased this house. I now maybe find only 1 or 2 grubs every year when I dig.
Also, I have noticed less Japanese Beetles on my roses and fruit trees. Defoliating a tree or bush stresses it. It doesn't kill it outright but repeated defoliation can eventually kill part or all of a tree or bush.
The first year I put out traps I would gather at least 1 gallon of Japanese Beetles per trap every week and I had out 3 traps. I trapped for 4 to 5 weeks. That's a lot of beetles.
The second year I put out 2 traps and collected 1/2 gallon in each milk jug every week. So you can that the number of beetles has dropped.
On to the trap itself. I use the Spectracide Japanese Beetle trap.
I replace the bottom portion of the bag with an empty plastic milk or fruit drink jug. See how the bag narrows and then flares out again. I make my cut about 2 inches beneath the narrow portion of the bag. You keep the top portion of the bag but attach a gallon milk jug using a twist tie. Tie beneath the threaded part of the milk jug because this will help to keep the milk jug attached to the plastic bag.
Add your attractant after you have the milk jug attached because it works so fast that beetles will be dive bombing you to get to the attractant. The attractant smells good, kind of like cloves. When you buy your bags make sure to get an extra attractant for every trap you put out. The kit comes with one but I find that they only last about a month.
Next, I attach the trap to a tomato cage. Why use a cage? It keeps the trap from blowing around in windy weather, it helps when you need to mow because it can easily be moved, and you can move it if you think it isn't seeing enough beetle action.
That round disc on the yellow portion is the attractant.
I remove my milk jugs the night before trash pick up day. I save the milk jug cap so all I do is remove the twist tie, put on the cap, say ewwwwwwwwwwww, and then throw it in the trash. Why not use the bag and dispose of the bag. First off, that would require buying new bags that are smaller than a milk jug. I have seen beetles crawl out of a filled bag before. With a bag, they can crawl out of if the bag gets ripped in the trash truck. Ewwwww
Look at how many are in this plastic jug!!!
With this method you will only buy the attractant every year. FYI look for the attractant at the end of summer when it goes on sale. The attractant is sealed and will last as long as you do not open it.
FYI this method does not work with the traps that have a ziploc bag. I found those to be the least effective in keeping the beetles in and not touching you when changing the bag. AND again if you use this type you will need to buy more bags.
How does the trap work? If you have ever watched a Japanese Beetle then you know that they are not the most graceful of flyers. The beetle smells the attractant and flies towards the sexy odor. They fly right into the yellow plastic, they drop down into the container, and then they can't fly back out.
You will need to change your plastic jug if it starts to smell from decomposing beetles. That odor will over ride the attractant and they will not be drawn to the trap.
Where do I place the trap? Place it away from the trees and bushes that they like to eat the leaves. I sometimes move my traps around if I find beetles in an area where I do not have traps. You will soon know where the hot spots are in your yard.
I remove my traps once the beetles disappear, which in our area tends to be mid August.
I hope that this helps you to rid your yard of the Japanese Beetle. This insect shouldn't be here. It is not indigenous to the U.S. and by trapping you are helping to keep the Japanese Beetle from destroying fruit trees. There are at least 300 species of plants that are a host for the Japanese Beetle.
Happy Trapping
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