I realized after my interview last weekend that I had never actually covered Japanese Beetle Bags on the blog! That omission must be remedied!
I’m sure you’ve seen them–they are for sale all over. The sad truth is that they don’t work.
Sure, they fill up the bag-o’-death in a really satisfying way, but they also attract many, many more beetles into the area that don’t get caught. As long ago as 1985, there was pretty clear evidence that putting the bags out actually made the damage from the beetles worse.
Beetle bags contain a combination of lures–the bright yellow color mimics flowers, there’s a feeding attractant, and also a female sex pheromone. It is the buggy equivalent of a giant flashing neon sign advertizing a message equivalent to “FREE SEX ORGY AND ALL YOU CAN EAT BBQ WINGS + BEER”.
A lot of beetles come to the trap–but less than 25% of the beetles attracted actually go into it.
Here, look at the data.
That’s from a 2009 study that looked at the specific behavior of beetles attracted to the trap. They concluded that it’s not a problem with trap design; it’s a problem with beetle brains. Scarabs are notoriously poor fliers; a few will probably bean you at top speed if you stand around outside long enough in the summer.
Their braking strategy is about the same as the one I use on rollerblades–find a large object, smash into it, and hang on.
So, thousands of Japanese beetles fly into the area where the trap is and most of them miss it. They hang around the trap–because they know that orgy must be around here somewhere–and eventually hook up and start eating. Outside the trap.
Some of them do eventually find their way into the bag later on, but the total catch is still pretty dismal. And you just paid money to bring all these pest insects into your yard. Oops.
One recommendation that’s commonly made, since the traps do work, just not the way we want, is to buy them and give them to the neighbor you hate the most. Then their garden will be gobbled up, and your beetles will all fly over there.
Sounds great, right? Except. Here is where the Karma comes in.
One of the reasons these beetles are so evil is they have a 1-2 punch. No only do they eat your fruit and veg, they lay their eggs in your yard. And eat your grass from the roots.
So, if you send all your beetles over to your neighbor’s yard with the traps…they will lay thousands of eggs over there. And even more beetles will come right back to you as punishment for your Karmic Transgression when the grubs emerge from his/her yard. Payback is a bitch.
So how can you control them? Honestly, I have had the best success with a Mason jar full of soapy water. Find a small kid and tell them you’ll give them a penny for each beetle in the jar. Problem solved.
You might also enjoy this video about Japanese Beetle Control created by the University of Maine. Ayup!
Switzer, P., Enstrom, P., & Schoenick, C. (2009). Behavioral Explanations Underlying the Lack of Trap Effectiveness for Small-Scale Management of Japanese Beetles (Coleoptera: Scarabaeidae) Journal of Economic Entomology, 102 (3), 934-940 DOI: 10.1603/029.102.0311
Gordon, F. C., & D. A. Potter (1985). Efficiency of Japanese beetle (Coleoptera: Scarabaeidae) traps in reducing defoliation of plants in the urban landscape and effect on larval density in turf. J. Econ. Entomology, 78, 774-778