Japanese Beetles on roses are a common problem for gardeners and rose enthusiasts alike.
These small, metallic green insects with copper-colored wings can cause significant damage to roses, often defoliating entire plants in a matter of days.
Their voracious appetites and tendency to congregate in large numbers make them a formidable foe, but with the right techniques and strategies, it is possible to manage Japanese beetles on roses and keep your garden looking beautiful.
Read on to learn more about Japanese beetles and how you can eradicate them from your garden.
What Are Japanese Beetles?
The Popillia japonica, more commonly known as the Japanese beetle, is a destructive pest that attacks your rose plants.
As their name suggests, the Japanese beetle is native to Japan, but it has since become invasive to Europe and North America where it feasts on rose plants.
Adult Japanese beetles are identifiable by their metallic green head and thorax, along with their copper forewings.
Underneath their wings, they have a thin line of white hair.
An adult can grow to roughly half an inch in length.
The larvae are not directly harmful to rose plants, but in due time they will mature into adults, so they are problematic nevertheless.
Japanese beetle larvae are 1 1/2” in length with a white grub-shaped body and a black head.
How To Distinguish Japanese Beetles On Roses From Other Common Garden Pests
Japanese beetles are not the only species of beetle that prey on rose plants.
Let’s take a look at a few other common rose pests and what separates them from Japanese beetles.
Cane Borer
Cane borers are long, skinny black beetles with red heads.
They differ from Japanese beetles by directly going after the canes of the rose (hence their name).
Cane borers dig their way into the branches of the rose plant, while the Japanese beetle remains on the exterior of the plant, preferring to feast on flowers and leaves.
Rose Chafer
The rose chafer beetle is comparable in size to the Japanese beetle, measuring 1/2”.
Just like the Japanese beetles, the rose chafer enjoys feeding on the roses’ flowers and buds.
While these two beetles are very similar, their main difference is their appearance.
Rose chafers are gray in color, as opposed to the metallic green and copper of the Japanese beetles.
Damage Caused By Japanese Beetles On Roses
Effects On Rose Bushes
Japanese beetles damage rose plants by feeding on rose flowers and buds.
While their primary source of food is the flower/bud, they are not opposed to feeding on the leaves if there are no other options.
Japanese beetles leave a path of destruction through your garden if they are left up to their own devices.
After they finish devouring your rose flowers, they will start to go after the leaves.
This voracious feast will absolutely devastate the infested rose plant.
Signs Of Infestation
Because of their larger size, it is easy to spot a Japanese beetle on your rose plant.
Keep an eye out for their metallic bodies.
It is especially important to monitor your plants if your roses are already in bloom, as flowers are the primary food source for these pests.
We recommend inspecting your plants once a week.
The best defense against Japanese beetles is early detection.
The sooner you can spot them and remove them, the less damage they can cause to your plants.
How To Get Rid Of Japanese Beetles On Roses
Chemical Methods
Chemical extermination methods are a great supplement to other control methods when it comes to Japanese beetles.
Select a pesticide containing rotenone-pyrethrum to effectively combat an infestation of Japanese beetles.
Other gardeners swear by using neem oil, which is a natural pesticide made from the extract from the neem tree.
Neem oil not only deters Japanese beetles from continuing to eat flowers, but it also contaminates larvae and stops them from developing into mature beetles.
Biological Control Methods
Because Japanese beetles are invasive to North America and Europe, there are no natural predators that could counterattack an infestation of adult beetles.
However, there are some biological controls that could exterminate the larvae population.
While the larvae do not directly attack rose plants, by controlling the larvae, you prevent them from developing into adult beetles that pose a threat to your plants.
Use predatory nematodes for a short-term control method, or for something more long-term, opt for a milky spore bacteria.
You’ll effectively wipe out those pesky larvae before they ever become a danger.
How To Get Rid Of Japanese Beetles Naturally
Japanese beetles are large enough that they can be picked off by hand as you spot them.
When you pick them off, drop the beetles in a bowl of soapy water to properly exterminate them.
DIY Solutions
Fruit Cocktail
Open a can of fruit cocktail and allow it to ferment for a week. Then, place the can in a light-colored bucket and fill the bucket with water just above the edge of the can.
Place the bucket about 25 feet away from your roses. The Japanese beetles will be more attracted to the sweet scent of the fruit and migrate towards the bucket, where they will be trapped by the water.
Soap & Oil Spray
In a bowl, combine: 1 teaspoon of dish soap 1 cup of vegetable oil 1 quart of water 1 cup of rubbing alcohol
Pour the mixture into a spray bottle and shake the bottle vigorously to mix it into a uniform spray. Use this spray every 10 days on pests.
Garlic Spray
In a blender, combine: 5 garlic cloves 1 teaspoon of dish soap 1 quart of water
Blend the mix until smooth and then strain out the mixture with a fine-mesh sieve. Pour the liquid into a spray bottle and spray pests as needed.
The Best Ways To Keep Japanese Beetles Away
The best way to keep Japanese beetles at bay is by early detection and prevention.
Always perform routine inspections of your rose plants for signs of any pest infestation (not just Japanese beetles).
Furthermore, pests are more likely to attack your plant when it is in poor health.
Defend your roses against an infestation by maintaining a healthy, fortified plant.
Plant your roses in full sunlight, keep the soil lightly moist, and fertilize twice a year and you’re sure to have a strong rose plant that can stand up to pest infestations.
Conclusion
Finding a pest infestation on your rose plants is never fun, and Japanese beetles are no exception.
We highly stress the importance of early detection and monitoring of your rose plants. If you happen to spot a Japanese beetle, time is of the essence to halt its path of destruction.
Whether you implement chemical or natural control methods, stopping this invasive beetle species is extremely important for the longevity of your roses.
