In the early 1900s, Japanese beetles came to the USA. Since then, they have become a common pest in the eastern states.
They are not fussy eaters – munching on flowers, trees, vegetables, and fruit – they feed on about 300 species of plant. The grubs emerge in spring to eat the roots of the grass, causing ugly brown patches in your lawns.
If they find your garden attractive, they can fly in from miles around!
So how can you prevent Japanese beetles from devouring your plants?
We have done the research to seek out the best insecticide for Japanese beetles. Here are our recommendations.
- Diatomaceous earth
- Scotts GrubEx1
- Demand CS
- Organic 100% Neem Seed Oil
- Compare-N-Save Systemic Tree and Shrub Insect Drench
What are Japanese Beetles?
Japanese beetles destroy plants both as adult beetles and as grubs. The adult beetles lay their eggs in the soil, and when the grubs emerge, they live beneath the surface, where they eat the roots of grass and other plants. You may find large brown patches of dead grass in your lawn or see that your plants are dying.
The Japanese beetle has three stages in its life – eggs, grubs, and adult beetles.
The female feeds during the morning, and in the afternoon, she lays her eggs in the soil.
One adult beetle lives about 30 – 45 days. The adults are most active in the hot days of June, July and August. They like to feed in the sunshine – so sunny days and plants exposed to the sun are their favorite haunts.
When the eggs overwinter in the soil, the babies hatch in spring and start eating the roots of grass and plants. In June, the grub changes into a pupa and then comes out into the open around July as an adult.
You might like to watch this 6-minute video about Japanese beetles:
(Sometimes people worry that Japanese beetles are causing damage to their plants- yet they never see them – it might be a different beetle, one that feeds at night like the Northern Masked Chafers.)
How to Prevent Japanese Beetles
It is a good idea to prepare in advance. By doing this, you have a head start in preventing the ravages of the Japanese beetle.
Prevention is more manageable than cure because there is a broader window of time when you can apply the insecticide. An ideal time between May and July can be effective – and since the insecticides work for a long time, some can continue to kill the pests for up to a year.
Be ready to apply your chosen insecticide at the first sign of beetle attack. Treat your garden between the laying of the eggs and the grubs hatching. The insecticide will kill eggs, pupae, and adults.
How to Get Rid of Japanese Beetles
Once you can see the beetles, you need to get rid of them as soon as possible. And choosing ht best insecticide for Japanese beetles is the first step.
You can spray soapy water onto the beetles to kill them. Spraying is easiest to do in the early morning before the beetles have released pheromones that attract yet more beetles to our patch. Also, the beetles are sluggish early in the day – you might be able to shake them off branches and into a bucket of soapy water where they will drown.
The most effective time to treat established Japanese beetles is in early to mid-August. The grubs are still immature and easy to reach since they are still close to the surface.
You can choose to spray the affected area, apply granules or a drench, or use a trap. Whichever method you use, be sure to read all the manufacturer instructions and follow them – this will ensure maximum safety to you, your family, and pets, as well as the environment.
Once you have used your insecticide, avoid contaminating water sources or sewage. Use all your product in your garden. Rinse the container and take them to the dump. Only buy what you will use! The best insecticide for Japanese beetles may be toxic to aquatic life.
If you rinse your soil before applying the insecticide, it will work better. Avoid using it when it is raining or about to rain – this can make the insecticide concentration too weak to be effective.
Sprays and Drenches
Practical and easy to use. Some come as concentrates, and you need to mix them according to the instructions. The drench pours around the base of a tree, so it stays local. You need to keep children and pets away from the area until it has soaked in and dried out.
You will need a spreader to ensure an even distribution for complete protection of our yard. Once the granules are watered in, they release the chemicals that will kill the beetles.
A trap works by releasing sex pheromones and a floral scent. These are very attractive to adult Japanese beetles – and that is their downfall. They attract beetles from nearby areas – so even your neighbor’s garden might benefit – but you will have about four times as many beetles as usual. Only around 60% will end up in the trap bag – and it really isn’t too pleasant disposing of a bag full of beetles!
Safe, effective, and incredibly versatile dust.
Diatomaceous earth consists of tiny, fossilized diatoms. They were formed in freshwater lakes and accumulated over thousands of years. This earth can now be mined and used in many different ways – including killing Japanese beetles. It is one of the best insecticides for Japanese beetles.
Diatomaceous Earth is a food-grade insecticide with no additives and registered for organic use (OMRI certified). It works by destroying the insect exoskeleton – so it acts on the adult beetles within 24 hours. The 10-pound size should be enough for medium to large-sized gardens, but it must remain dry to be effective. If it does get wet, no worries – once it has dried out again, it retains effectiveness.
- Natural product
- People with Asthma should mask up before using it
- It does not work while wet
Four months control after one application.
Apply these granules in late spring or early summer for four months of freedom from Japanese beetles. Chlorantraniliprole is the active part, and it kills the Japanese beetle grubs, even before they damage your lawn.
You may need a hand spreader to apply the granules evenly, and they need to be watered in and allowed into the soil.
If you aren’t satisfied with the results, Scotts offers a money-back guarantee.
One application of these granules in the late spring or early summer will give you four months of control of Japanese Beetles in their white grub stage, killing them before they damage the turf in your yard. You will need a hand spreader to cast the granules.
- One bag covers 10,000 square feet
- Last for four months
- Money-back guarantee
- You may need to buy a spreader
- The granules need to be watered-in
- Children and pets at risk until dry
The lethal spray killing Japanese grubs and adults.
This spray is one of the most versatile products, making it the ideal insecticide for both adults and grubs.
The active ingredient is lambda-cyhalothrin, which kills over 30 pests, including Japanese beetles.
Demand CS says you can use this spray in food prep areas, but one should always read and follow the instructions supplied with the pack.
It does suggest that this product safer than many other insecticides you can buy.
- One bottle will last an average homeowner for over a year
- It kills Japanese beetles and their grubs
- May need a sprayer to apply correctly
- Should not be used on edible plants
Organic 100% Neem Seed Oil
Natural, non-toxic insecticide.
Neem oil is listed for organic farming and has the Organic Materials Review Institute (OMRI) qualification. This product is 100% cold-pressed Neem oil.
While Neem oil is an effective insecticide against the adult Japanese beetle, the effects only last a few days, so you have to keep reapplying it. If the temperature drops below about 70ºF, the oil may solidify – no problem, immerse the bottle in warm water for a few minutes and then shake vigorously.
- 100% natural ingredients
- OMRI listed for organic farming
- Very effective against adult Japanese Beetles
- May solidify below 70ºF
- Only effective for a few days
- A powerful garlic odor
Compare-N-Save Systemic Tree and Shrub Insect Drench
The ideal drench for trees and shrubs.
Compare-N-Save is an ideal insecticide if you have Japanese beetles on your trees or shrubs – but it is not so effective on grass. You can use this on listed trees and nut trees, and one application can last as long as a year. The trees absorb the insecticide through their roots – it enters the plant, and the insects eat it – and die.
The active ingredient is imidacloprid, which kills many other pesty insects, and is highly toxic to bees. All you need to do is mix the concentrate with water and pour it around the base of the tree. This insecticide is absorbed through the roots and into the plant for protection that won’t wash off.
- One application lasts up to a year
- Easy to use
- It can’t be washed off
- Toxic to bees
You can attack Japanese beetles both early in their life cycle in spring – or later when they have become adults –and the grubs have already got going on the root of your lawns. So a two-pronged attack is best.
- Diatomaceous earth you can trust - Our obsession to create the purest food Grade diatomaceous earth affects every aspect of our business, from the quality of the deposits we mine from, to the stainless Steel equipment that handles the De.
- The only official supplement - we are the only producers of food grade diatomaceous earth products that meet all requirements for health supplements in the USA
- 100% organic - all of our products are certified organic by the organic minerals review Institute
- Nature's most diverse product - diatomaceous earth is an amazing powder that can be used for a wide range of applications from health supplement to pet care. Take a look at some of our reviews for a more thorough list of benefits and use cases
- Wholly produced in the USA - our entire process from mining to filtering to packaging is all completed in the United States
You might apply the insecticide in spring to kill off the grubs and follow through with Neem oil or Demand CS, killing both grubs and adults very effectively.
We would hesitate to use a bee-killer like Compare-N-Save. However, the one application that lasts a year is very attractive, and the manufacturers say that – provided you follow their instructions – you can limit the damage to bees.
However, our first choice for the adult beetle is the very versatile DiatomaceousEarth 10 LBS FOOD GRADE Diatomaceous Earth - 100% Organic All Natural Diamateous Powder - Diametaceous for humans is Safe Around Children.. It is non-toxic, and OMRI listed. The granules are easy to use, although you might need a spreader, and it only works while it is completely dry. And for the grubs – use Scotts GrubEx1 in the spring.
Are Insecticides For Japanese Beetles Dangerous To Children or Pets?
Both children and pets are small and live closer to the ground. Infants crawl around, and some pets dig and sniff. Children’s livers are immature, so they are less able to detoxify products. It’s safest to keep them away from treated areas until the pesticides have dried completely – but always follow the manufacturer’s instructions.
Will Japanese Beetles Ever Go Away?
Adult Japanese beetles live for about two months, from late June to September, and then in the cooler weather, they die off. But they will have laid their eggs in the soil where they last the winter through.