Using Marigolds To Keep Japanese Beetles Away [Step-By-Step]


Japanese Beetles on Plant Leaf With Holes in Leaf

Let’s cut right to the chase: Japanese beetles are pests! They feed on the leaves and stems of plants, leaving them looking like lace with tons of holes, and eventually killing them. Farmers and amateur gardeners alike need solutions to protect their plants from these flying pests!

Marigolds can effectively keep Japanese beetles away from other plants in your garden. Japanese beetles prefer to feed on marigolds, so you should a bed of marigold flowers near your favorite plants so the beetles will gravitate towards the marigolds instead of the rest of your garden.

Before we look at how to use marigolds to protect your garden from Japanese beetles, let’s understand why beetles are such problems in the first place. Aren’t they just like every other annoying bug? The good news is that you can achieve a symbiotic relationship with Japanese beetles in your life by providing them pretty marigold flowers to munch instead of your other garden plants!

Why Do You Need to Keep Japanese Beetles Out?

Like so many other creepy crawlers and wild critters, the main reason that Japanese beetles are such pests is that they eat and kill plants that you’re trying to grow.

Mainly, they feed on the undersides of leaves. Think way back to high school biology: do you remember why the undersides of leaves are so important?

Just in case you don’t, it’s because this part of the plant is home to stomata, which allow plants to take in carbon dioxide. Carbon dioxide is vital for photosynthesis, the process by which plants make food. In other words, without stomata, the plant starves.

Japanese beetles can feed on other parts of plants, too, including the stems and pods. In short, beetles kill your plants, which is enough of a reason to keep them away. But there’s more.

Even worse than harming your plants, Japanese beetles can invade your house. That’s right—you could accidentally carry beetle larvae inside on your fresh-picked plants. Once they fully develop, they will seek out food wherever they can find it, which means that they might start to eat your other fruits and vegetables, grains, or even wood. Yikes!

Speaking of wood, there are types of beetles (called Lyctid beetles) that, when they infest a home, feed on all types of hardwood, including the hardwood that makes flooring, cabinets, doors, furniture, and molding and framing. As a result, they can cause a plethora of damage to your home.

Signs Your Garden Has a Japanese Beetle Infestation

The good news is that Japanese beetle infestations are relatively easy to recognize. The most noticeable tell-tale sign is holes in the leaves of your plants. As soon as you see holes in leaves, you know you’re likely dealing with some kind of garden pest, so it’s time to start digging deeper.

If you suspect that Japanese beetles may have invaded your garden, you can look for the larvae. Typically, Japanese beetle larvae have elongated, pointy bodies, are brown or brownish-white, and are seen lying on their sides in a “C” shape. They kind of look a bit like caterpillars!

For another thing, adult beetles aren’t typically tiny. The breeds and species of beetles commonly found in the United States range in size but are generally 1/3-1/2 an inch in length, at least. So, you’re probably going to see them with your naked eye.

More specifically, Japanese Beetles have a rust / green tint, and you’ll notice them buzzing veraciously near your plants or your head.

It would be best if you also ruled out some other pests whose handiwork resembles that of the beetle, including cabbage worms, slugs, and snails.

How Do Marigolds Deter Japanese Beetles From Your Garden?

French Marigold Up Close

Marigolds work as an insect and beetle repellent in two ways:

  1. They repel many types of insects—there are many types of insects that do not like the smell of marigolds and will stay away from them. These include whiteflies and nematodes. In addition, rabbits (another common garden nuisance) don’t like them either.
  2. They attract beetles away from other plants—specifically Japanese beetles, which are common in the United States, actually find marigolds to be a delectable treat. They’ll fill up on marigolds first and leave your other plants alone (in theory, at least).

For us, we’re going to focus on method number 2 and work to attract beetles AWAY from your favorite plants.

How To Use Marigolds to Keep Japanese Beetles Away

You will need to make space in your garden for the marigolds. You will also need to experiment with different planting patterns to determine what works best for you and your garden. We will cover two main methods (you can also utilize both).

Plant Marigolds Throughout Your Garden Bed

Method #1: Plant marigolds sporadically throughout your other plants—Using this method, you would stagger marigolds throughout your garden beds.

  1. Buy marigold plants. We recommend buying fully grown marigold plants so that you don’t have to wait for them to germinate and grow.
  2. Plant the marigolds throughout garden beds. You want to plant them near perimeters rather than among the other plants you’re trying to protect. Leave some space (at least 6 inches) between them and your other plants since both need room to grow and area for roots. In addition, you don’t want the Japanese beetles to move easily from your marigolds onto other plants.
  3. Maintain the marigolds. While marigolds are annuals, they self-seed, which means that they will continue to grow. They can spread and even begin to choke out your other plants if you’re not careful.
  4. Replace marigolds as needed. Even though they self-seed, you may occasionally need to buy and plant more of them since they are annuals. That said, most will bloom for a couple of months and only die when frost sets in.
  5. Observe the Japanese beetle population. If you’ve been experiencing too many Japanese beetles in your garden, then you should notice them begin migrating over to your marigolds. Otherwise, you may need to take other steps to get rid of your beetle problem.
  6. Be careful replanting in spring. Last year’s marigolds will have left seeds behind, which may end up popping out of the ground in the mid-late spring. For that reason, you should give them a little time before replanting. That will save you time and money and prevent waste.

Pros of this method:

  • Marigolds will distract any Japanese beetles that decide to inhabit your garden, drawing them away from more valuable plants.
  • Marigolds repel or kill other harmful insects.
  • Marigolds make a lovely aesthetic addition to your garden beds.

Cons of this method:

  • You might end up attracting beetles into your garden, which will then feed on your other plants when they’re done with the marigolds.
  • You have to be careful that the marigolds themselves don’t become invasive.

Plant a Bed of Marigolds Away From Your Main Garden Bed

Method #2: Plant a bed of marigolds—The other method for using marigolds to prevent a Japanese beetle infestation in your garden is to plant a separate bed of marigolds away from your main garden beds.

  1. Buy marigold plants. It’s easier to buy marigold seeds and plant them if you’re using this method rather than the first, but we still recommend full-grown plants that you can plop right into the ground.
  2. Choose a spot for your bed of marigolds. Marigolds are pretty hardy, but they need plenty of sunlight to thrive. Otherwise, they may end up growing mildew that will eventually kill them. So, choose a sunny corner of your garden or yard and plant away.
  3. Maintain your bed of marigolds. Most of the same set of parameters applies here as above, although you don’t have to be as worried about keeping the marigolds away from your other garden plants.
  4. Replace your marigolds as needed.
  5. Carefully observe. Surprisingly, this step is often missed. Just because others have had success using marigolds doesn’t mean that you necessarily will as well. That’s why it’s important to carefully observe whether your other plants are more protected from Japanese beetles or whether you still see signs of them in your garden beds.
  6. Replant your marigolds in the spring.

Pros of this method:

  • Keeps Japanese beetles away from your garden beds and other plants.
  • You don’t have to worry about spacing marigolds away from other plants.
  • You get a beautiful bed of marigolds in your yard.

Cons of this method:

  • Marigolds might drive other bugs closer to your garden since they are repelled by their smell.

The Downside of Using Marigolds To Deter Japanese Beetles

Single Japanese Beetle On Leaf With Bite Holes

There is always a downside, and when it comes to using marigolds in your garden for pest control, especially with beetles, it’s that you’re not actually dealing with the infestation. In fact, you might even make it worse.

Since Japanese beetles like marigolds, you’re providing them with one of their favorite foods. They’re unlikely to seek a new home if they’re getting everything they need from your garden. What’s more, if they’re thriving and healthy, they’ll continue to breed. Eventually, the population may become invasive and feed on your other plants after all.

As with so many other things in life, when it comes to gardening, practice makes perfect. It’s all about trial and error and finding what works, so give marigolds a try, but keep in mind what we said above: carefully observe to see if it’s effective for you.

Benefits of Using Marigolds To Deter Japanese Beetles

Besides the fact that they may work to keep beetles away from your other plants, there are a couple of other reasons why marigolds are so great to use.

For one thing, they’re pretty! Even though you have to be careful about where to place them in relation to your other plants, no one will look at them and know that you have a big problem.

For another, it’s an all-natural solution. No pesticides are needed here!

In addition, marigolds won’t just protect your garden from Japanese beetles. They also repel mosquitos and cabbage worms and attract snails and spider mites away from other plants.

Finally, while even the most die-hard animal rights activists aren’t terribly concerned about bugs, you get the satisfaction of knowing that you didn’t kill anything. That’s very nice of you!

Does It Matter What Type of Beetles I Have?

The answer is probably. That said, there aren’t extremely significant differences between the types of beetles you’re likely to find in the United States. Marigolds are effective for Japanese beetles primarily.

What Are the Best Types of Marigolds to Use?

Most gardeners who use the marigold method have found that French marigolds and Gem marigolds are the most effective for Japanese Beetles. However, since there are so many other factors and variables at play, you may need to experiment with different types to find the best combination for you.

In addition, not all types of marigolds will grow well in your garden, so you also obviously need a type that will thrive.

Other Plants That Repel or Attract Japanese Beetles

In addition to marigolds, there are other plants that can be used effectively to fight a Japanese beetle invasion. Try one or more of these:

  • Basil – bonus, you get to use it in your cooking.
  • Dill – use it to make pickles! It’s unclear whether the smell of dill is unappealing to insects or whether its strong scent masks other, more attractive plants, but either way, it works.
  • Garlic and onions – again, it might be the strong smell, but many bugs hate these plants. Onions of all kinds will work, including their close relative, leeks.
  • Larkspur – a pretty flower in purple, pink, or white.
  • Lavender – there’s a veritable lavender craze right now, with all of the great uses for this wonderful plant. Make essential oils, cleaning supplies, bath soaks, and much more.
  • Mint.
  • Parsley.
  • White geraniums.

Additional Tips for Keeping Japanese Beetles at Bay

If you’re in the midst of serious beetle mania in your garden, you probably need to take more drastic steps to get rid of them than just planting marigolds.

Use a beetle trap. You can buy beetle traps at most lawn and garden stores, as well as big-box home suppliers and online retailers. There are bags made specifically for trapping Japanese beetles.

Water and dish soap. Mix a teaspoon of dish soap into a quart of water and spray onto plants. It’s harmless for the plants but will suffocate beetles. We recommend Dawn brand dish soap, as it is free from chemicals and safe for animals.

Apple cider vinegar. Apple cider vinegar, is there anything you can’t do? Beetles tend to avoid this strong-smelling element, so you can spray it onto most plants. Just be sure it won’t harm them first.

Fruit cup. That’s right, those sugary, syrupy fruit cups that you ate as a kid are also good for attracting beetles. Once they climb inside to eat the delicious food, they get trapped in the stickiness. Keep in mind, though, that a fruit cup is going to attract much more than just beetles—you’ll have a cup crawling with critters in no time.

Other bugs. Wasps may be scary, and flies may be a nuisance, but one good thing about them both is they feed on other bugs, including beetles. You may not want to kill them so fast, after all.

Birds. Birds are probably a more appealing solution than other bugs. Birds also eat beetles, and you can encourage birds to visit your yard by putting out bird feeders and providing some shallow water to splash in (such as a fountain or birdbath).

Milky spore. Milky spore is a disease that can be easily spread to beetles and deadly for them. It can be purchased at lawn and garden centers and applied once every year. This is more of a preventative measure than a short-term solution.

Hand-pickingCertainly not for the faint of heart, but beetles are relatively large and not hard to see, so when you do see them, you have the option to pick them off and dispose of them yourself… if you can catch one!

References

Jauron, R. (1996). Marigolds. https://hortnews.extension.iastate.edu/1996/3-15-1996/mari.html

Hadley, C. H., & Hawley, I. M. (1934). General information about the Japanese beetle in the United States (No. 332). US Department of Agriculture.

Wilkin, D. and Akre, B. (2015). Leaf Structure and Function—Advanced. CK-12. https://www.ck12.org/biology/leaf-structure-and-function/lesson/leaf-structure-and-function-advanced-bio-adv/

Potter, D. A., & Held, D. W. (2002). Biology and management of the Japanese beetle. Annual review of entomology, 47(1), 175-205.

Wang, Y., & Gaugler, R. (1998). Host and penetration site location by entomopathogenic nematodes against Japanese beetle larvae. Journal of invertebrate pathology, 72(3), 313-318.

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