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Garden Enemy #1- Japanese Beetles

Updated: Apr 30

Move over, spiders — Japanese beetles are quickly becoming one of the most feared pests in America (for avid gardeners, at least). These pests will spend their whole life tormenting your landscape, from the time they’re grubs (aka white grubs) eating your lawn’s roots to when they become adult beetles and chew holes in all your trees and shrubs.

But you don’t have to resign yourself to that torment. You can prevent Japanese beetles if you think ahead and take some fairly simple precautions.

1. Control grubs

You can prevent adult Japanese beetles by exterminating the larvae, or grubs, before they ever have a chance to mature.

When to treat grubs: Grubs are active in the lawn in early spring and early fall.

Use these methods to get rid of grubs before they become Japanese beetles:

  • Neem oil

  • Lawn-aerating sandals

  • Beneficial nematodes

  • Milky spore

  • Attracting birds

2. Stop watering your lawn

Japanese beetles will lay eggs in your soil, and those eggs need moisture to survive. The fewer eggs that survive, the fewer adult beetles you’ll have in your garden later.

So, you want your lawn to be as dry as possible during the beetles’ egg-laying season, which is usually June through August. During that time, stop watering your lawn and let it go dormant so the eggs die instead of hatching.

Disclaimer: A dormant lawn isn’t exactly pretty. Your grass will eventually start to yellow if you stop watering it, but if it’s healthy, it should spring back to life when you resume watering. One summer without a green lawn could be worth ending the cycle of grubs and Japanese beetles.

3. Install row covers

Keep your plants covered with row covers during the Japanese beetle’s feeding season, which varies depending on where you live but usually lasts from June through August. The covers will physically block beetles from reaching your plants.

WARNING: Row covers also keep pollinators off your plants. Don’t cover plants that need to be pollinated.

4. Plant Japanese beetle-resistant plants

You can plan your garden from the beginning to resist Japanese beetles. They’re less likely to infest your garden if you choose plants that they don’t like.

Some plants that don’t attract Japanese beetles are:

  • Lilac bushes (Syringa spp.)

  • Dogwood trees (Cornus spp.)

  • Burning bush (Euonymus alatus)

  • Magnolia trees (Magnolia spp.)

  • Forsythia shrubs (Forsythia spp.)

Note: There’s no guarantee that Japanese beetles won’t attack these plants, but they’re less likely to attack these than other types of plants.

5. Use homemade Japanese beetle repellent sprays

One way to prevent Japanese beetles in your garden is to spray your plants with a smell that repels them. There’s no need for chemicals — you can make your own repellent at home.

Here are some recipes you can try:

  • Garlic spray: Crush six or more cloves of garlic (depending on how concentrated you want the spray to be) and pour a gallon of boiling water over it. Leave the garlic to steep overnight. Strain out the garlic pieces, then put the water in a spray bottle.

  • Cedar spray: Add a few ounces of cedar oil to 5 gallons of water. Pour some of the mixture into a spray bottle.

Whichever homemade spray you make, spray it liberally on your plants to repel Japanese beetles. You’ll have to re-spray every few days and after rain or heavy dew washes off the repellent.

How to get rid of Japanese beetles once you already have them

You might end up with Japanese beetles in your garden despite your best efforts, but don’t worry — you can get rid of them.

These are some of the best methods for getting rid of Japanese beetles:

  • Hand-pick them off your plants and drop them in a bucket of soapy water.

  • Spray your plants with raw neem oil.

  • Make your own pesticide spray with dish soap, vegetable oil, and rubbing alcohol.

  • Leave out dead beetle bodies to repel the live ones.

  • Collect live beetles using a drop cloth.

  • Attract natural enemies to help control the Japanese beetle population.

  • Plant geraniums, which paralyze Japanese beetles when ingested, in your garden.

  • Plant a “bait” garden to keep Japanese beetles away from your prized plants.

  • Set up Japanese beetle traps far away from your garden.

  • Apply chemical insecticides to your plants.

How to tell if you have Japanese beetles

You’ll know if you have Japanese beetles because they leave very noticeable damage to your lawn and garden. Once you understand when Japanese beetles are active, you can keep an eye out for signs of damage and the bugs themselves.

1. Can Japanese beetle traps prevent an infestation? No. In fact, Japanese beetle traps are attractants, and they only catch about 75% of the bugs they attract. Traps are more likely to cause an infestation than prevent one.

2. What scent repels Japanese beetles? The best scent to repel Japanese beetles is the “death stench” of dead beetles. If possible, collect some dead Japanese beetle bodies in small containers and place them around your garden. If dead beetles aren’t an option (we get it — yuck!), here are some other scents that repel Japanese beetles: —Cedar —Garlic —Chives —Tansy —Catnip

3. Does vinegar deter Japanese beetles? Vinegar sprays can kill Japanese beetles, but they also kill your plants. We don’t recommend using vinegar directly on your plants, and you would have to spray it directly on the leaves for effective Japanese beetle control. Even horticultural vinegar isn’t safe to use on your plants. Horticultural vinegar has a higher acetic acid content than household vinegar, which means it’s even better at drying out plants and killing them. This product is intended to kill weeds, not to use on plants for pest control.

4. What plants do Japanese beetles eat? Japanese beetles eat more than 300 plant species across several plant families. Some of their favorite plants are rose bushes, grapevines, hibiscus, and raspberry.

Make the first move on Japanese beetles in your garden

You’d be surprised how quickly a group of Japanese beetles can chew through all the leaves and flowers in your garden. That’s why the best course of action is protecting your garden before they ever set their greedy little eyes on it.

If your area is prone to Japanese beetle attacks, you’ll want to take preventive measures like the ones we described above every year beginning in spring. Stay one step ahead of these buggers, and you’ll save yourself a whole summer of pain!

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