Japanese beetles are common pests and can quickly infest your garden. Since they’re an invasive species in the US, they don’t have any natural predators that will control their population. Plus, they’ll eat just about any plant in sight.
To use neem oil to get rid of Japanese beetles, you should first select your chosen neem oil variety, and apply it correctly. You’ll also need to continue applying the neem oil each week until the beetles disappear. Stopping the treatment early will cause them to come back.
Neem oil is an excellent option for driving away this invasive species. This article covers how to use neem oil effectively on Japanese beetles, so keep reading!
1. Understand When and How Neem Oil Works
Neem oil works best when you catch a Japanese beetle infestation early on. If the infestation becomes too large, it won’t be nearly as effective. If that happens, you’ll likely need to find another method to deal with the beetles.
Japanese beetles also follow a feeding cycle. They usually eat between 9 am and 3 pm during late June and August. After that point, they typically start to die. You should use neem oil during those months. You should also apply it at night, so it’s already there when they start feeding. Plus, applying the neem oil at night prevents your plants from burning from the sun shining on unabsorbed oil.
Neem oil can stop Japanese beetles from eating and laying eggs, significantly reducing the number in your garden. You shouldn’t expect to see instant results, so it’s essential to be patient. It will take several days to see a decline in the beetles.
Why Insects Hate Neem Oil
Most insects despise neem oil and will stay away from it. Neem oil has this effect because it contains Azadirachtin, an insecticide sourced from the neem tree. It has several effects on insects that make it excellent for gardens. Plus, it’s a natural material, so it shouldn’t disrupt your plants much.
Azadirachtin destabilizes several hormones in insects, which have these effects:
- Prevents feeding
- Disrupts growth so larvae can’t become adults
- Prevents molting
Neem oil has such a strong scent that it often repels pests before they’re anywhere near your garden or plants.
Overall, it disrupts the hormones of insects that touch it, so they can’t take over your property. Since Japanese beetles can’t multiply extremely fast, neem oil is perfect.
How Fast Do Japanese Beetles Multiply?
Japanese beetles multiply extremely fast, so you’ll need to act as soon as you spot them in your garden. A female beetle lays about 50 eggs during a two-week period. The beetle eggs take a few weeks to hatch. They only need a month to become adults and continue the cycle.
So, it won’t take very long for the Japanese beetles to take over your garden completely. They’re also very destructive in both their larvae and adult forms. The beetle larvae eat the roots of your grass and plants, while the adults will eat the actual plant and any flowers for fruits that it produces. It doesn’t take many Japanese beetles to kill a plant, either.
In short, it can take less than a month for Japanese beetles to destroy your garden, making it essential to start the neem oil treats when you notice just a few of them on your plants.
Why Use Neem Oil Instead of Insecticides
You should consider using neem oil instead of insecticides because traditional pesticides typically contain harmful chemicals for humans and the environment.
Many home gardeners prefer to use natural insect repellents whenever possible to reduce the risks for themselves, especially when spraying them on their food.
Neem oil isn’t dangerous to people when you applied to plants. Plus, it won’t harm the environment like chemicals can. It’s even safe for a person to eat produce from a plant treated with neem oil. Simply washing the vegetable can remove any trace of oil from the outside.
It’s a great natural alternative to any insecticides you think of using on the beetles.
While neem oil is considered a safe and effective insecticide and fungicide for plants, applying it isn’t ideal for some plants as it can burn their leaves. Find out which plants you shouldn’t apply neem oil on in my other article: 5 Plants You Shouldn’t Use Neem Oil On
2. Select Your Preferred Neem Oil Variety
Neem oil comes in various forms, but the most effective varieties for eliminating Japanese beetles include cold-pressed oil and neem oil cakes. Most gardeners prefer straight oil because it’s more versatile since there are more ways to apply it. However, neem cakes can remove Japanese beetle larvae living in the soil. So, there are cases where you can benefit from using both.
I’ll break down these two types of neem oil below:
Cold-Pressed Neem Oil
This form usually comes to mind first when you think of neem oil. It usually comes in a plastic jug as a liquid. You can add the oil to water to create a solution that you spray on your plants. Or, you can soak it in your garden’s soil to eliminate any beetles in the ground.
Japanese beetles don’t like the smell and taste of this oil, so they’ll start to avoid it. 100% cold-pressed neem oil also disrupts their hormones and can prevent them from coming back. However, you’ll need to apply it weekly and spray the oil all over the plants, including under their leaves.
Neem Oil Cakes
Neem cakes are a bit different. They’re small pellets that you can apply to your garden’s soil, where they kill pests living there. This feature makes them best for removing Japanese beetle larvae, so you should use it before the bugs emerge in the summer.
The cakes are also fertilizers, so you’ll need to consider how they impact your garden. Most brands use an NPK ratio of 6-1-2. Some plants may not like those nutrient ratios, so you must be careful. You also won’t need to use the cakes as frequently as the pure oil.
Applying neem oil to the soil can help prevent root rot and other plant diseases.
3. Apply the Neem Oil
Next, you’ll need to apply the neem oil. There are three ways to use it, depending on what form of neem oil you choose.
Here are all the different ways to apply neem oil to your plants:
Create a Neem Oil Spray
The easiest option for most people is to create a neem oil spray. You can do this by mixing water and oil in a spray bottle. Here are the steps:
- Mix one quart (946 ml) of warm water with one teaspoon of neem oil in a large container.
- Add a small amount of Castile or dish soap to emulsify the oil to combine with the water.
- Stir the neem oil solution until combined.
- Use a funnel to pour your neem oil solution into a spray bottle.
Once you have your neem oil spray, mist the affected plants in your garden with the solution. It shouldn’t leave a residue behind and dries quickly.
Choosing a high-quality cold-pressed oil is also important to get the best results. The Plantonix Neem Bliss Pure Neem Oil from Amazon.com is an excellent option. It has many uses, is organic, and works well against garden pests.
Make a Neem Oil Soak
Larvae could be underground chewing the plants’ roots even if you’re not seeing any adult beetles around your plants. Luckily, there are a few ways to deal with the grubs causing havoc in the soil.
You can also use cold-pressed neem oil to drench the soil. It will repel any Japanese beetles nearby. The plants absorb the oil through their roots, making them much less appealing to these pests.
It’s also a simple process. You can follow these steps:
- Combine a gallon (3.79 liters) of water with one tablespoon of dish soap in a large bucket.
- Stir until combined.
- Add two tablespoons of 100% cold-pressed neem oil to the bucket and mix.
- Place a cup or two of the mixture in the soil surrounding your plants.
- You want the ground to be drenched.
- You can use as much of the solution as you need, but be careful not to overwater your garden.
Neem oil that the plants absorb through their roots lasts longer than spraying it on the plants. You can get away with doing a soil soak every three weeks instead of every week.
Most gardeners find it most effective to combine these two methods. You can start by spraying the plants with neem oil, then soaking the soil. That way, they’re protected from the Japanese beetles until they can absorb enough oil.
Use Neem Cakes
Different brands might have varying instructions, so make sure that you check before using them. Most of the time, you’ll apply the cakes to the soil’s surface, as you do with fertilizers. Afterward, you’ll need to water your garden so the neem oil can seep into the earth.
From there, the neem cakes work similarly to creating a neem oil soak. The oil will kill larvae living under the surface, and the plants absorb the neem oil, making them less attractive to Japanese beetles.
It’s the best option if you also need to fertilize your plants when dealing with these pests.
4. Monitor the Japanese Beetles
While getting rid of the Japanese beetles, you’ll need to keep an eye on them. You’ll need to keep spraying the plants every week or adding the neem oil to the soil every few weeks for it to be effective. Applying neem oil isn’t a one-time solution.
If it doesn’t seem like the Japanese beetles are leaving, you’ll want to give the neem oil some more time to work. Combining several application methods to ensure the neem oil reaches all Japanese beetles is also good.
After a few weeks, you should notice the Japanese beetle population shrinking. However, you shouldn’t stop the applications of neem oil. If you accidentally quit applying the oil too early, the beetles will return. Even if you only see a few beetles on your plants, you need to keep using the treatment, which is why monitoring them is crucial.
Japanese beetle infestations can sometimes become too large for neem oil to solve. You should contact the professionals for help in those cases.
5. Reapply the Neem Oil Often
After applying neem oil, you’ll need to reapply it frequently. It can wash away in the rain and becomes less effective with time. Japanese beetles will return in full force if there’s not enough neem oil to drive them away.
Here’s when to reapply the neem oil, depending on the form that you used:
- Neem oil sprays: You’ll need to respray the plants every week. Keep using the oil spray for a few weeks after all the beetles seem gone. Make sure you reapply at night to avoid disturbing any beneficial insects.
- Neem oil soaks: You’ll need to do another neem oil drench every three weeks. This time allows your plants to absorb the oil without becoming overwhelmed by it. Plus, it keeps the oil in effect in the soil, so new beetle larvae don’t appear.
- Neem oil cakes: You only should use the neem cakes once a month. Since they’re also a fertilizer, using them more frequently could lead to you overfeeding your plants.
6. Neem Oil Monthly for Beetle Prevention
Once you’ve gained control of the Japanese beetle situation, you must apply neem oil monthly to your plants. Doing so can prevent the insects from returning and ruining your garden.
At this point, the plants should’ve absorbed enough neem oil to help keep the beetles away. Plus, since they’re only active in the summer, the beetles might’ve started to die on their own.
You’ll also want to use neem oil in your garden before the beetles return in late June. You can help prevent them from taking an interest in your plants by adding the oil as a preventive measure. Since the larvae live in the soil during the fall and winter, there might still be a few waiting to emerge and eat your crops when it gets warm.
Overall, neem oil is excellent for preventing infestations. It works more efficiently when there are fewer beetles to manage, so applying it during the start of June is best. From there, you should continue reapplying as usual.
Are Japanese Beetles Harmful to Gardens?
Japanese beetles can be extremely harmful to any garden. They’re a pest, so they’re tough to get rid of, and they’ll eat anything you plant. Japanese beetles even eat grass roots, which can cause a lot of damage to your lawn. If you notice these beetles on your property, nothing you have planted in your garden is safe.
Certain plants are more at risk of attracting Japanese beetles, although they’re known to eat several hundred types of plants. If you have these in your garden, you might have issues with beetles often:
- Apple trees
- Cherry trees
The beetles can quickly destroy crops, parks, and golf courses, so it won’t take long to ruin a small garden. They’re so destructive because they’re an invasive species in America. That means they have no natural predators here and can quickly spread. So, if you see them in your garden, you’ll need to act fast to get rid of them.
Are Japanese Beetles Good for Anything?
Japanese beetles do kill flea larvae living in the soil. So, if you have pets, these beetles might reduce the odds they get infested with fleas. However, Japanese beetles are an invasive species here, so they don’t offer many benefits to our environment.
Japanese beetles contribute much more to their native environment. Since they’re not originally from here, there aren’t many benefits to having them around. As an invasive species, they cause a lot of harm to crop growth and compete with native insects for resources.
Overall, there aren’t many benefits to having Japanese beetles on your property, and this pest will do a lot more harm than good. While they might eat flea larvae, they prefer what your garden offers much more.
What Is Neem Oil Used For?
Neem oil is used as a pesticide or repellent. It has a powerful sulfuric smell that most insects hate. Plus, it can disrupt insect hormones so they don’t lay more eggs. You can find it in a ton of products today. However, many gardeners prefer to use oil in their organic gardens.
Since it’s an organic material, it’s safe for the environment even though it’s an insecticide. You won’t need to worry about it hurting your garden when you use it properly.
In conclusion, you can use neem oil to get rid of Japanese beetles. The oil drives away the bugs and disrupts their life cycle. They hate the smell and won’t eat any plants you spray the oil on. However, you do need to apply the oil regularly to get these effects.
The Japanese beetles should leave as long as you keep a routine with applying your neem oil. Keeping consistent will give you the best results.