I checked with Mario Bertelmann, one of our horticulturists, and here is what he shared:
"I have done some digging on this question and it does not appear that this claim has been proven. There are mixed reports as to whether 4 O’clock flowers attract/kill Japanese beetles. However, studies on zonal geraniums have shown more promising results as the flowers contain a rare excitatory amino acid that temporarily paralyzes the beetles, leaving them susceptible to predators. Below is a link to the USDA site where it discusses the use of geraniums to combat Japanese beetles as well as a link to a scientific peer reviewed study on the effects of geraniums on Japanese beetles."
Hi Rachael,
I checked with Mario Bertelmann, one of our horticulturists, and here is what he shared:
"I have done some digging on this question and it does not appear that this claim has been proven. There are mixed reports as to whether 4 O’clock flowers attract/kill Japanese beetles. However, studies on zonal geraniums have shown more promising results as the flowers contain a rare excitatory amino acid that temporarily paralyzes the beetles, leaving them susceptible to predators. Below is a link to the USDA site where it discusses the use of geraniums to combat Japanese beetles as well as a link to a scientific peer reviewed study on the effects of geraniums on Japanese beetles."
https://www.ars.usda.gov/news-events/news/research-news/2010/geraniums-could-help-control-devastating-japanese-beetle/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3029778/
Thanks for the question!
Doris Boardman
Website & SEO Manager