Can Japanese Beetles Eat Roses and How to Manage

Japanese beetles can be a nuisance, especially when it comes to roses. Japanese beetles are known to feed on the leaves and flowers of roses, causing damage and discoloration.

Their preference for roses is due to the plant's tender new growth, which is high in protein and easy to digest. This makes roses a prime target for Japanese beetles.

In fact, Japanese beetles can consume up to 1,000 leaves per month, which can weaken the plant and make it more susceptible to disease and pests.

Suggestion: Japanese Beetle Rose Damage

Japanese beetles are notorious for their voracious appetites, and they'll eat just about anything in their path. They love roses, and from what I've heard from my garden coaching clients, they're also big fans of Hibiscus syriacus, also known as rose of Sharon.

These beetles will eat over 300 species of plants, from root to flower. Their larvae will munch on the roots, while the adults will consume everything else. I've seen them ravage entire gardens, leaving nothing but destruction in their wake.

Japanese beetles are particularly fond of fruit and shade trees, roses, shrubs, asparagus, corn, soybeans, and a variety of other vegetables and ornamentals. They'll even eat geraniums, but interestingly, these plants contain a substance that temporarily paralyzes the beetles, making them susceptible to predators.

Here's a list of some of the worst plants to grow if you're dealing with Japanese beetles:

It's worth noting that the U.S. Department of Agriculture (USDA) has identified these plants as being particularly appealing to Japanese beetles in their Japanese Beetle Program Manual.

Japanese beetles are stocky and range from about 3/8 to 1/2 inch long, with a metallic green body and coppery wing covers. They have a distinctive row of white spots along each side of the abdomen just below the wing covers, as well as two white spots on the back end of the abdomen.

To manage Japanese beetles, start looking for them in your yard and garden starting in late June and early July. This is when they first appear, so it's essential to start management early to minimize damage. Damaged leaves attract more beetles, so minimizing beetles on plants should mean fewer beetles will be attracted to them.

Japanese beetles feed for six to eight weeks, so it's crucial to continue management until their numbers decrease. Most feeding is finished by mid to late August. If you're looking to replace plants that are frequently damaged by Japanese beetles, consider using one of the many plants that they seldom damage, such as boxwood, clematis, or conifers.

Here are some plants that Japanese beetles seldom damage:

Adult Japanese beetles are stocky and range from about 3/8 to 1/2 inch long. They are metallic green with coppery wing covers.

A row of white spots along each side of the abdomen just below the wing covers, as well as two white spots on the back end of the abdomen, are distinctive characteristics of Japanese beetles.

These spots can help you identify Japanese beetles with certainty.

Japanese beetles have a distinctive larval stage, known as white grubs. These grubs are typically C-shaped and white to cream-colored.

One way to identify white grubs is to look at their body shape. They are usually C-shaped, which is a distinctive feature.

White grubs have a distinct tan-colored head, making them easily recognizable. This is a key characteristic to look for when searching for Japanese beetle larvae.

The size of white grubs can vary, but they are usually between 1/8 inch and one inch long. This range is typical for Japanese beetle larvae.

Here are some key characteristics to look for when identifying white grubs:

Japanese beetles can be very abundant in some years and less in others. Their feeding season typically starts in late June and early July.

It's essential to start management when they first appear, as damaged leaves attract more beetles, making it harder to control the population. Most feeding is finished by mid to late August.

To effectively manage adult Japanese beetles, it's crucial to continue management until their numbers decrease. Consider using a less preferred plant when choosing new plants for your landscape, as some plants are less appealing to Japanese beetles.

For your interest: Japanese House Plants

Some plants that Japanese beetles seldom damage include boxwood, clematis, chrysanthemum, conifers, daylily, geranium, ginkgo, Japanese tree lilac, forsythia, common lilac, magnolia, red and silver maple, oak, white poplar, redbud, rhododendron, and yew.

Here are some plants that Japanese beetles usually don't damage:

Japanese beetles can be controlled on roses using a combination of methods.

Hand-picking is a simple and effective way to control Japanese beetles on roses, especially for small infestations.

Japanese beetles are most active during the summer months, peaking in June and July, which is also when roses are in bloom.

Insecticidal soap or neem oil can be applied to the soil around the base of the rose bush to control Japanese beetle larvae.

Check this out: Grub Control for Japanese Beetles

Japanese beetles can be a real nuisance, but the good news is they rarely kill your roses. They may weaken your plants over time, making them prone to secondary pest infestations or diseases.

One simple and free remedy is to knock the beetles off your roses and into a bucket of soapy water. This is most effective early in the season.

Knock the beetles off in the early morning or late evening when they're less active. This way, they won't have a chance to send out signals to other beetles that your garden is a good place to eat.

If you'd rather let the pros handle it, you can hire a state-licensed applicator to use professional-grade products to lower the population in your yard.

Curious to learn more? Check out: How to Keep Japanese Beetles off Roses

Low Risk Insecticides can be a great option for controlling Japanese Beetles on your roses. Pyrethrins, found in products like Pyola, are somewhat effective contact insecticides, but be sure to spray them directly on the insect and avoid harming bees and beneficial insects.

Repeat applications are necessary with Pyrethrins, and Neem oil is another option that's effective for several days, although repeat applications are also needed. Neem oil is low risk to bees and other beneficial insects.

Bacillus thuringiensis galleriae, derived from soil bacteria, is moderately effective against Japanese beetle adults, providing one to two weeks of protection, and it's not toxic to bees and other beneficial insects. This product is only available from online sources.

Expand your knowledge: Neem Oil Japanese Beetles

If you're looking to plant a new rose garden or replace existing rose bushes with Japanese beetle-resistant varieties, there are some great options to consider. Dr. Cranshaw's research identified three categories of roses: "Not Recommended", "Maybe", and "Recommended".

Roses in the "Not Recommended" category had both high levels of beetle damage and high bee visitation, making Japanese beetle control difficult and insecticide application unwise. These roses include 'Easy Does It' and 'Eureka' in the Floribunda category, and 'Elle' in the Hybrid Tea category.

On the other hand, roses in the "Maybe" category had no bee visitation and varying levels of beetle damage, making them effectively treatable with insecticidal controls. These roses include 'Cathedral' and 'Class Act' in the Floribunda category, 'Tuscan Sun' in the Hybrid Tea category, and 'Midas Touch' in the Miniature category.

Roses in the "Recommended" category had no beetle damage, making them a great choice for gardeners looking to avoid Japanese beetle control issues. These roses include 'Angel Face' in the Floribunda category, 'Colossus' in the Hybrid Tea category, and 'Carrot Top' in the Miniature category.

You might like: Floribunda Rose Bushes

Here's a summary of some Japanese beetle-resistant rose varieties to consider:

Keep in mind that this is not an exhaustive list, and there are many more rose varieties that need to be explored for their susceptibility to beetle damage.

Japanese beetles are a significant pest, and understanding their habits can help you prevent damage to your roses. Japanese beetles feed on over 300 species of plants, including roses.

These beetles are notorious for their voracious appetites, and they can cause significant damage to your garden. They chew on leaves, flowers, and fruit, leaving behind a trail of destruction.

Here are some quick facts to keep in mind when dealing with Japanese beetles:

It's worth noting that Japanese beetles are an invasive species, and their populations can fluctuate from year to year. In Minnesota, for example, the Minnesota Department of Agriculture (MDA) trapped over one million beetles in a single year.