Japanese Beetles Rose Damage – How To Get Rid Of Japanese Beetles On Roses
By: Stan V. Griep, American Rose Society Consulting Master Rosarian, Rocky Mountain District
By Stan V. Griep
American Rose Society Consulting Master Rosarian – Rocky Mountain District
There is nothing more frustrating to the rose loving gardener than this nasty pest from the land of the rising sun known as the Japanese beetle. A beautiful rose bed one day can be turned into a field of tears in just moments by an attack of these garden bullies. Let’s look at some ways on how to control Japanese beetles on roses.
How to Get Rid of Japanese Beetles on Roses
I have read about various methods to try to control and be rid of them from covering all the roses with a tight woven mesh netting to hanging Bounce dryer sheets in the rose bushes.
After all the reading I have done about Japanese beetles and rose damage, it appears that one of the best ways to attack them is a two pronged approach. At the very first signs of any Japanese beetles entering your area, not even necessarily your rose beds or gardens, buy a product called Milky Spore. This spore is eaten by the Japanese Beetle Grubs and has a bacterium that kills the grubs. Upon killing the grubs, even more of the milky spore is generated, thus helping to kill even more grubs. This method can take three to four years to spread enough through the garden areas, depending upon the size of the garden, to make the impact desired on these bullies.
If going this route, it is extremely important to use an insecticide to kill the adult beetles that will not kill the grubs as well. Killing the grubs that eat the milky spore slows up or stops the spread of the milky spore and, thus, can negate its impact upon the beetles you are trying to gain control over. Even if your rose beds are heavily under attack, the milky spore seems worth a try.
Spraying and killing the adult beetles prior to them laying their eggs to start the cycle all over again is of great importance as well. The use of products called Sevin or Merit to spray are a couple of University Test Lab listed choices, being careful to keep the spray application high to mid range of the bush and not directly on the ground or base of the bush. Move quickly with the spraying so as not to get a lot of over spray or dripping onto the ground below.
Another choice of insecticide might be one called Safer BioNeem, which has shown some real promise in control.
There are some plants that seem to repel the Japanese beetles, perhaps adding some of these plants in and around the rose bushes would be to your advantage as well. These include:
How Not to Get Rid of Japanese Beetles on Roses
I do not recommend that anyone use the Japanese beetle traps that are on the market though. You may well be calling more than you currently have into your rose beds or gardens by using them. If you really want to use them, I would place them at the far end of your property and far away from anything they can damage.
Research that was conducted at the University of Kentucky indicated that the Japanese beetle traps attract several more beetles than are caught in the traps. Thus, the rose bushes and plants along the flight path of the beetles and in the same area of the traps placement are very likely to incur much more damage than if no traps are used.
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Got iridescent green beetles feasting on your roses? Those would be Japanese beetles! Here are tips on how to identify and get rid of Japanese beetles.
What Are Japanese Beetles?
Japanese beetles (Popillia japonica) are small insects that carry a big threat. They do not discriminate when it comes to what types of plants they feed on, though they do have favorites (like roses). In fact, they are classified as a pest to hundreds of different species. They are one of the major insect pests in the Eastern and Midwestern United States, causing monumental damage to crops each year.
Prior to the beetle’s accidental introduction to the United States in the early 1900s, the Japanese beetle was found only on the islands of Japan, isolated by water and kept in check by its natural predators. In 1912, a law was passed that made it illegal to import plants rooted in soil. Unfortunately, the failure to implement the law immediately allowed the Japanese beetle to arrive in this country.
Most entomologists agree that the beetles entered the country as grubs in soil on Japanese iris roots. In 1916, these coppery-winged pests were first spotted in a nursery near Riverton, New Jersey, and by 1920, eradication programs were dropped the beetle proved to be too prolific and widespread.
When to Look for Japanese Beetles
Before you go to battle with Japanese beetles, make sure you know the enemy. These insects have an iridescent green head and thorax (the part of the body right behind the head) and glossy, copper brown wing coverings. Look for fuzzy white patches along both sides of their abdomen. There are several look-alike beetles that don't have the white spots.
Start watching out for Japanese beetles in May or June, and continue looking for them into August. They are often actively feeding in the morning and late evening. They tend to be most active when temperatures are over 85°F and the air is still, so keep an eye out for new beetles coming into your yard during these conditions. You might not see very many beetles on cool, rainy days, but don’t assume the beetles are gone. A warm, sunny day often will bring a resurgence. A proactive approach that involves checking regularly for them and controlling them right away is essential for managing Japanese beetles.
Japanese Beetle Control Methods
Now that you have a better understanding of the Japanese beetle and a quick look at what methods are used to control the Japanese beetle, it’s time to dig into the heart of each tactic.
Let’s jump right into the Japanese beetle control methods.
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1. Physical Removal – Handpicking
When beetle numbers are low and have infested only small plantings, one of the most practical Japanese beetle control method is to remove them by hand. If the plant is sturdy enough and damage won’t be inflicted, you could try shaking them off. Ensure to have a container below to trap them in. It makes no sense to shake them off the plant, only to have them re-infest it. You can drop the beetles in soapy water to kill them.
Make it a habit to check your plants every day and handpick beetles when you see one to lessen feeding damage to your plants. Keep in mind that damaged leaves remit chemicals in the air that attracts more beetles to your plants. By removing Japanese beetles physically, you’ll prevent or minimize new beetles from flocking to your ornamentals.
While lady bugs and other beetle types are known to bite, research shows otherwise for the Japanese beetle. However, if you’re scared or doubtful, wear gloves when handpicking.
2. Creating a Physical Barrier – Netting
This Japanese beetle control method is quite simple and effective when used alongside handpicking.
When you use a physical barrier, you are preventing Japanese beetles from further latching on to your plants.
Let’s say you’ve just recently handpicked all the Japanese beetles from your plants. To prevent a re-infestation, simply use a physical barrier. A physical barrier could mean covering your roses with a cheesecloth. Fine netting can also be used.
While this method can prove effective for specific plants, it must be done with care. Plants that are in bloom will require pollination. If you cover up these plants, pollinators won’t be able to get to them. But, there is a workaround to it if you want to use this method. Simply continue handpicking Japanese beetles until your plants have started to set fruit, then you can now cover them with fine netting .
3. Setting Lures and Traps
You can also buy traps from garden centers if you wish to try lures and mechanical traps to eradicate Japanese beetles. There are two types of commercial traps you can choose from. One kind of trap uses a bait that mimics the smell of virgin female beetles, which will highly attract male Japanese beetles. Another trap variant uses bait that has a sweet smell of food type that can attract both males and females. Both types of trap can attract thousands of beetles daily.
While this method of Japanese beetle control might have some success, it could backfire. Some Japanese beetle traps actually capture fewer beetles than those lured, as some beetles tend to fly around the trap. Plus, if these lures and traps are assembled close to gardens and plants beetles are attracted to, more harm than good can be done.
If you do opt to use this Japanese beetle control method, ensure you’re setting up the lure and trap far away from garden and plants.
Traps can also be effective when you use many of them and spread over a certain area.
You must also keep in mind that traps must not stay in place all year long because lures in them get stale. Placing a trap should also be done around June and August, during the flight period of Japanese beetles.
4. Cultural Control
Female Japanese beetles will most likely lay eggs on moist soil since moisture is essential for the survival of eggs, as well as larval development. During the dry season, female beetles will look for irrigated areas to deposit eggs.
You can try suppressing the beetle population by manipulating their habitat and make it less suitable for them. Holding off irrigation may decrease the white grub population. In addition, rotating the soil to at least 3 to 4 inches deep during fall can also lessen the chances of larvae survival.
Plant Japanese beetle resistant plants like geraniums to discourage their numbers
5. Resistant and Susceptible Plants
As mentioned earlier, Japanese beetles feed on a number of plant species. However, there are some species that they aren’t that interested in. Choosing a Japanese beetle resistant and susceptible plant for your landscape is what you may consider when you want to add new plants. Although this Japanese control method isn’t a treatment, it’s a strong preventative. If you can cultivate crops and plants that they aren’t a fan of, you’ll see them in fewer numbers, if at all.
Plants that are less preferred by Japanese beetles include boxwood, chrysanthemum, clematis, conifers, daylily, geranium, ginkgo, lilac (Japanese tree and common lilac), magnolia, maple (red and silver), oak, and yew.
Side Note: If you have a lot of roses planted in your garden, expect a lot of trouble.
6. Chemical Control
There are several pesticides you can choose from to get rid of Japanese beetles. However, before choosing this method, there are certain factors you need to consider. You need to assess and know the benefits, as well as the risks of using insecticides.
Knowing when and how to apply insecticides is crucial for a successful pesticide application. Remember that pesticides are toxic, so you need to follow carefully and exactly what the label direction says. Improper use of pesticides can lead to serious hazards to both humans and wildlife.
Another risk you should know in using pesticides is the growing concern of water contamination due to pesticide runoff. You can try checking the agricultural chemicals handbook where you’re residing, as each State has its own that’s being updated every year for proper pest control recommendations.
Some of the chemicals you can use for adult Japanese beetles include bifenthrin , carbaryl, cyfluthrin, deltamethrin , and permethrin . On the other hand, imidacloprid, halofenzide, trichlorfon, and chlorantraniliprole are the chemicals you can use for larvae. When treating plants using chemicals, be sure to thoroughly treat flowers and foliage.
Using this Japanese beetle control method in the afternoon when Japanese beetles are usually active will lead to optimal control. Take note that repeated applications may be needed to prevent re-infestation.
Side Note: If you do opt to use pesticides, bear in mind that this can affect beneficial insects such as birds and pollinators.
It’s best to use low-risk pesticides. Products containing pyrethrins are effective, provided they’re sprayed directly on to plants. Do not spray bees and other beneficial insects.
Another option to use is neem oil . You will need to apply regularly for several days for the best result. Although neem oil is a deterrent and may keep Japanese beetle at bay, it’s more difficult to repel them when they infect your garden in large numbers.
Another option to consider is residual insecticides. These have a longer effect when used against Japanese beetles.
A Japanese beetle residual insecticide that provides protection for up to four weeks is chlorantraniliprole (Acelepryn) . Plus, this has a low risk to insects like bees. Other options insecticides with the following chemicals:
- Carbaryl or acephate
7. Biological Control
If you’re not a fan of chemicals, you can try this Japanese beetle control method. Using fungi, nematodes, parasites, and other biological control agents can be a successful way to control beetle population.
Using biological control agents might take some time to take effect as compared to pesticides, but this method lasts longer. Also, it is not harmful to beneficial organisms, unlike pesticides.
Biological pesticides are parasitic in nature and includes Heterorhabditis bacteriophora. These nematodes affect Japanese beetle grubs and need to be applied to the soil when grubs are present.
Another option includes milky spore bacteria (Paenibacillus popilliae, also known as Bacillus popilliae). The milky spore bacteria only affects Japanese beetle grubs, and not beneficial organisms.
Japanese beetles may be small pests, but they can definitely be a big problem. Using various Japanese beetle control methods can help you minimize these pests, and protect your plants, fruits, and ornamentals. Choose the right method, or a combination of Japanese beetle control methods, for your situation and it can help you lessen the damage caused by this pest.
How to Identify Japanese Beetles
Japanese beetles live in all states east of the Mississippi River. You can recognize the adults easily: They have metallic blue-green bodies about 1/2-inch long, with bronze wing covers, long legs, and fine hairs covering the thorax.
Larvae are fat, dirty white grubs with brown heads often found in sod. They grow up to 3/4 inch long. Many other species produce C-shaped white larval grubs, so make sure you've actually got Japanese beetles and not some other helpful insect species before waging war.
The grubs move from deep in the soil toward the surface in the spring to eat roots, pupating in early summer. Adults then emerge, feed on the plants, and lay eggs in late summer. Finally, their eggs hatch into larvae that overwinter in soil. One generation occurs every one to two years.
The damage you're noticing can also help you identify Japanese beetles. Adults munch on flowers and skeletonize leaves of a broad range of plants. They also feed on fruit such as raspberries and plums, opening a site for disease infection. Larvae feed on the roots of lawn grasses and garden plants.
Dealing with Japanese Beetles
Are these nasty pests devouring your favorite flowers and plants this summer? Here’s what you can do to stop them.
Every summer, questions pour in to us regarding the Japanese Beetles that are voraciously devouring people’s flowers and plants. It’s quite obvious these little buggers are the culprit. Their ¼” long bodies are easy to spot and since they are very slow moving, you’ll likely catch them in the act. Their shiny metallic green and copper shells glisten in the sun like rare jewels but beauty can be deceiving! They don’t seem to care a bit that they are destroying our favorite roses, hibiscus and clematis flowers.
Japanese Beetles are a major summer pest throughout the Central, Midwestern and Northeastern United States and Canada. They live as grubs in your soil from fall through winter, then emerge as beetles between early June and late August. Your local extension agent will have more specific information for the timing of Japanese Beetles in your area. Once they emerge as beetles, they chew large holes in flowers and foliage to the point where they will even eat every last leaf off of the plants they love. Members of the Rose family are their favorite targets.
As is the case with most pests, there are a variety of ways to try to control Japanese Beetles. Focusing on prevention is key since their hard shells make them tougher to kill once they have turned into beetles. Here are a few things you can do to control Japanese Beetles in your garden.
Before Japanese Beetles emerge, they are grubs that live under your lawn and in your garden beds. So prevention means getting to the grubs before they can grow up into beetles and spread all over your garden. There are lots of options for controlling grubs. The following can be purchased at garden centers or online.
- Grub-eating Nematodes (Heterorhabditis bacteriophora) – These beneficial nematodes find grubs in the soil and kill them.
- Bt (Bacillus thuringiensis) - Bt is a naturally occurring soil bacteria that eats Japanese Beetle grubs before they can develop into beetles.
- Milky Spore (Bacillus papillae)—This bacterium takes 2-4 years to become established in the landscape but then offers continuous protection from Japanese Beetle grubs.
This method is not for the squeamish! Most people don’t want to touch bugs, but Japanese Beetles do not bite and you can pick them off plants and either bag them or drop them into a bucket of soapy water to get rid of them. It is easiest to do this early in the morning before the beetles wake up and start moving.
There are traps you can buy at home improvement stores which are made especially for Japanese Beetles. The way they work is by luring the pests into a small container from which they cannot escape. This can work to help reduce the beetle population, but don’t leave the trap out all the time (maybe just a day or two a week) as it will attract all the local bugs to your garden and that can be a LOT of beetles. Since the beetles may feed on nearby plants before entering the trap, do not set the trap out near your favorite plant. Instead, place the trap at the edge of your yard away from the plants the beetles may damage. Make it a neighborhood effort as traps become more effective if there are many scattered throughout the area.
Select chemicals can be effective at controlling Japanese Beetles. Least toxic to humans and pets are the Pyrethrin class of insecticides which are safe to use on vegetables, grapes, raspberries, flowers, roses, trees and shrubs but can be very bad for fish, so avoid using them around ponds. Another low toxicity control method is applying Neem Oil as a spray as soon as the beetles appear in your garden. Neem Oil can help control Japanese Beetles, Cucumber Beetles, Flea Beetles, Cabbageworms, and Colorado Potato Beetles.
Planting Resistant Plants
Japanese Beetles seem to try a taste of just about everything in the garden, but there are actually a select group of woody and herbaceous plants that they typically leave alone. Consider this list when adding new plants to your garden if you are plagued by Japanese Beetles.
RESISTANT to Japanese Beetles
VULNERABLE to Damage from Japanese Beetles