How To Kill Japanese Beetles

Jul 13, 2020 | Garden, Maggie Lane Designs

This is a re-post:  I thought this was important to send out again so we can all be better prepared.  I was at Lowe’s this weekend talking to the help in the Lawncare department when the topic of Japanese Beetles came up.  I asked about Neem Oil (since I’ve used it in the past – see below) and was told this product is flying off the shelves.  I guess people are bracing themselves for another summer of beetles.  The last two years have been difficult trying to get them to leave my yard alone.  I hope it’s different this year.  They were so bad that it looked like a blanket of beetles hovering over our yard.
Considering I’ve had some experience with these pesky little things, I added more information about how and when they lay their eggs, releasing pheromones, and using Japanese Beetle Bags to kill them.  Trust me they work!
Does GrubEx prevent Japanese Beetles? (I used this product this past April so let’s see what happens.  I also made sure to treat the areas of the yard in sections so the dogs would not step in or accidentally get this product in their paws or mouths)
Using Scotts® GrubEx®1 Season Long Grub Killer annually can also help control Japanese beetle and Armyworm infestations. Easily apply with a Scotts® broadcast, drop, handheld, or Wizz® spreader and stop grubs before they damage your lawn.  (see more information below)
Happy Monday everyone!  The one thing that I love the most about this summer is looking out over our patio, porch, and property and seeing all of our hard work coming to life and blooming in colors.  I spent days putting our patio planters together with several trips to Bedners Greenhouse in McDonald, PA.  What a wonderful place!  And now…I’m dealing with an infestation of Japanese beetles!!!  They are on the rise this year and let me tell you, it is real!  I am seeing clusters of beetles on my poor rose bushes and I’ve noticed that they have now ventured over to my potted plants and hanging baskets.  I called our local greenhouse and did some research on the web and was told to use Neem Oil.  I bought one bottle at Lowe’s and one bottle on Amazon and have gone through both already. I’ll be making another trip this week.  I’ve provided information and links below on homemade treatments as well.  Although Neem Oil will not hurt the dogs, I keep them inside while using this product as it requires you to drench the leaves and flowers with a spray bottle.  I do not want to risk getting oil into their eyes, nose, and mouth or them possibly tracking it into the house on their paws.  I just want to be safe.
What are Japanese Beetles?
Japanese beetles (Popillia japonica) were first found in the United States in 1916, after being accidentally introduced into New Jersey. Until that time, this insect was restricted to Japan where it is not a major pest. This pest is considered to be an invasive species. It is now found throughout the eastern U.S., except for Florida, and continues to move westward.
Adult Japanese beetles feed on the leaves, flowers and fruits of many different plants. Preferred plants include rose, grape, linden, apple, crabapple, cherry, plum and related trees, birch, elm, raspberry, currant, basil, Virginia creeper, hollyhock, marigold, corn silks and soybean.

Adult Japanse Beetles

  • Approximately 1/3 to 1/2 inch long.
  • Metallic green head and thorax (the area behind the head) with copper-brown wing covers.
  • Sides of abdomen have five white patches of hairs, and tip of abdomen has two patches of white hair.
How to manage an infestation of Japanese Beetles
  • Start looking in your gardens and lawn late June early July
  • Damaged leaves attract Japanese beetles so make sure your shrubs, flowers, and plants are treated
  • Japanese beetles feed for six to eight weeks so it is important to continue management until their numbers decrease. Once they are present in large numbers, managing them becomes more difficult.
  • Most feedings are finished by mid to late August.

Larva (white Japanese grubs)

  • C-shaped, white to cream-colored grubs with a distinct tan-colored head.
  • Legs are easy to see.
  • From 1/8 inch up to about one inch long.
  • Japanese beetle grubs look like other white grubs and can only be positively distinguished by examining the pattern of spines and hairs on the underside of the tip of the abdomen.
  • Grubs chew grass roots and reduce the ability of grass to take up enough water and nutrients to remain healthy. When grub feeding is severe, dead patches of grass develop.
  • Controlling Japanese beetle grubs is unlikely to reduce numbers of adults on landscape plants because beetles emerging from non-treated grass areas can fly considerable distance to preferred adult food plants. Only treat white grubs to protect lawns from damage.
Did you know that once beetles die, the living beetles do not like the smell of the dead ones?
The smell of dead Japanese beetles acts as a repellent to other Japanese beetles.  Let containers of dead beetles (the ones you hand-pick or collect in traps) sit near desirable plants or around your yard.  This will help repel them.
Where do Japanese Beetles lay their eggs?
Egg laying occurs mainly in July and August in the vicinity of the feeding sites.  A female lays 40 to 60 eggs in her life, preferring moist soil with grassy cover. The female beetle digs about 10 cm into the soil several times over a period of about two weeks, each time laying eggs in small batches.
Don’t squish the beetle to kill it.
Beetles attract more beetles through pheromones, which are so powerful they can attract beetles from a few thousand feet. If you squish a Japanese beetle, you run the risk of releasing the female beetle sex pheromone.
How Japanese Beetle Traps Work
Japanese beetle traps release both a sex pheromone and a floral scent, are very effective in attracting adult beetles. They fly to the trap in droves, where they crawl or fall into the bag and can’t get out. You simply dispose of the bag, and put on a fresh one, and the process starts all over again.


Learn how and when to treat Japanese beetles and grubs with Blain’s Farm & Fleet.
The immature stage of the Japanese beetle – the white grub – typically has a three year life cycle. However, most of the damage to ornamentals and turf grass happens during the spring and fall the second year. This is when grubs are present in the top inch of the root zone, heavily feeding on grass roots and thatch. In the third year of the cycle, the grubs rise out of the soil as Japanese beetles. These beetles feed on surrounding plants and lay eggs in the soil throughout the summer. These eggs eventually hatch into grubs and the cycle begins again.

What is Neem Oil?
Neem oil is a naturally occurring pesticide found in seeds from the Neem tree. It is yellow to brown, has a bitter taste, and a garlic/sulfur smell. It has been used for hundreds of years to control pests and diseases. Components of neem oil can be found in many products today. These include toothpaste, cosmetics, soaps, and pet shampoos. Neem oil is a mixture of components. Azadirachtin is the most active component for repelling and killing pests and can be extracted from neem oil. The portion left over is called clarified hydrophobic Neem oil.
I followed the instructions on the back of the bottle but it is highly recommended that you drench the plant in Neem Oil using several applications over a period of time.  The oil should be dripping from the leaves and it is best to use Neem Oil in the morning when the beetles are most active or in the evening when the sun is not so hot.  You do not want the oil to hit the leaves and the sun hit the oil and burn your plant.
Japanese beetles are slow moving which is a plus because you can literally pick them off the leaves or knock them into a bucket of Dawn dish soap and hot water to kill them.  I checked into buying beetle traps and my first thought was…wouldn’t that bring more.  It turns out that most of the articles I read say the same thing…the traps do not deter the beetles from flying in but only bring more.  If you do buy a trap, make sure it is placed far away from the plants you are trying to save.

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  1. Patty

    I am battling the same problem! They are so bad this year, destroying my rose bush and patio plants too! Between them and the rabbits, it’s a full time job protecting my flowers!

    • Bobbi

      I am so sorry. I hope the Neem Oil helps you and your yard.


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