I’m one of the fortunate few Minnesota gardeners who — at least so far — does not have a problem with Japanese beetles. The JBs can be extremely frustrating and they have driven two of the most peace-loving ladies I know to near distraction.
There are lots of rumors about what works and what doesn’t work with the beetles. Hand removing works; traps, probably not. But here are two things you may not know about getting rid of Japanese beetles.
A friend of mine has been squishing the beetles when she pulls them off of her roses. This was good therapy for her. Unfortunately, it turns out the beetles emit a scent when they are crushed and — you guessed it! — the scent attracts more beetles.
Another example: Several experienced gardeners have noted that geraniums appeared to be toxic to Japanese beetles. They wondered if putting the geraniums near other plants the beetles like, such as roses or raspberries, would protect those plants. It turns out that there is some truth to this. According to the University of Minnesota Extension, a substance in geraniums seems to paralyze beetles — almost as if they were drunk. But, like drunkenness, it’s a temporary condition and eventually they recover. Also, the beetles don’t learn from their mistakes — they keep coming back to the geraniums. Some research even shows having geraniums nearby brings on more beetles.
The good news is, the beetle season in Minnesota is at least half over.
How do you deal with JBs?
I shoo the beetles off into a bucket of soapy water. Their natural instinct is to drop when threatened so they tend to jump of the plant right into the bucket below them. They cannot fly out of the bucket once wet so they drown.
Thankfully, the JB season now seems to be over. I like to drown them — there’s a kind of grim satisfaction in it. This year we put the trap further away from the roses, so fewer JP came to the roses (it only took 2 years to get smart about that!).
Yes, the numbers do seem to be way down. Good idea about moving the traps away from the roses. Thanks for commenting!
Is there research on the dead beetles attracting more beetles? There seems to be little evidence.
This study from the University of Kentucky is the one most frequently cited: https://academic.oup.com/jee/article-abstract/78/4/774/2214392?redirectedFrom=fulltext
Mary Sheir, the article you cited does not mention squashing the beetles, releasing an attracting scent, does it? At least, the abstract does not mention this. I guess I don’t really know the mechanism of the traps – I supposed they were already suffused with some kind of pheromone, not just the dead beetle scent of the trapped beetles. Or is the mass of dead beetle bodies the attractant? Is there any research regarding squashing the beetles as an attractant?
Here’s a fact sheet that explains the traps a bit — the yellow panels at the top of the trap have a floral scent infused in them that attracts the beetles. It is not the dead beetle scent. https://extension.colostate.edu/docs/pubs/insect/05601.pdf