The much-reviled Japanese beetles (Popillia japonica) are one of the most notorious garden pests of the summer. These iridescent green insects pose a serious threat because they feed on a wide variety of plants, wreaking havoc on flowers, vegetables, shrubs, and trees.
Although they are generally harmless to humans, no gardeners want them around. That’s why most people will find a way to keep them away or get rid of them.
Surprisingly, an attractive flower that seems to need the aid of the sun to thrive has been observed in connection to the campaign against Japanese beetles. What’s more, the flower is a favorite for these nuisance insects. And that’s the geranium.
Geraniums are a favorite of Japanese beetles, but they seem to hold the key to controlling the devastating Japanese beetles. When beetles consume geranium petals or leaves, they are paralyzed and may die.
This post will in-depthly cover how geraniums help gardeners control Japanese beetles.
How geraniums could help control Japanese beetles
Geraniums are known to contain geraniol, a monoterpenol alcohol that is incredibly effective at attracting beetles.
That said, while Japanese beetles feed on a number of ornamental plants and shrubs, they readily munch on geraniums to consume the bait. Little did they know they were meeting their doom when dining on geraniums.
So, how do geraniums help in controlling Japanese beetles?
The geraniol oil that attracts Japanese beetles to geraniums is also what poisons them.
When Japanese beetles consume geranium foliage or flowers, the geraniol content puts them in a narcotic state. Precisely, within a half-hour or so of consuming geranium petals or leaves, these devastating insects roll over on their back, their legs and antennae twitching slowly, and they remain paralyzed for several hours, typically 12 -24 hours.
Notably, although beetles usually recover within 24 when paralyzed under lab conditions, in gardens, they are more likely to die after ingesting the geranium leaves as they contain natural chemicals.
In their paralyzed state, they are also more susceptible to predators that devour them while helpless. If you spot paralyzed Japanese beetles, you can collect and crush them.
Note: If you are planting geraniums to control Japanese beetles, it is best to plant them in full sun. It is believed that the sun intensifies the toxic effect of geraniol oil in geraniums.
How to kill Japanese beetles on Geraniums
While Japanese beetles that ingest geranium flowers or foliage are more likely to die than survive, you may want to kill them before they consume your attractive flower. Thankfully, killing them is pretty simple.
Pour 4 cups of water into a small pan, and mix about ½ cup of dish detergent into it to make it appear soapy, not bubbly. Approach the geranium garden early in the morning when the beetles are sluggish and less likely to fly away.
Holding the soapy water under the geranium plant, shake the plant’s foliage, so the Japanese beetles fall inside the water. The detergent will keep the insects from climbing out of the pan.
After collecting the beetles, you can crush them or let them drown.
If the infestation is heavy, spray your geraniums and nearby plants using a pyrethrum-based pesticide. Spray every three or four days, and this should control the population. When it comes to spraying, follow the instructions on the label for effective results.
Pro tip: Don’t plant geraniums around roses, especially if your goal is to control Japanese beetles and other pests. Both geraniums and roses plants have geraniol content that attracts Japanese beetles. Planting them close together will only attract a higher population of beetles that can be hard to control.
Other ways to get rid of Japanese beetles
Geraniums offer an easy and inexpensive way to control the devastating Japanese beetles. However, this may not work for every gardener, especially in northern climates where geraniums don’t grow well.
If you are struggling with Japanese beetles, any of these methods would be of great help:
- Spraying with neem oil – best for killing Japanese beetles before they mature
- Set traps far from targeted plants – this helps to lure male beetles, eventually killing them before they can mate.
- Use row covers during the peak feeding period
- Pick the Japanese beetles off plants by hand
Related Article: Where Do Japanese Beetles Go At Night?