How to Handle Japanese Beetles

One of the less fun aspects of maintaining a beautiful garden is dealing with the pests that want to treat your hard work as their lunch. Of these pests, the Japanese beetle has proven to be quite a difficult one to protect against. In this blog we will cover what you can do to prevent them from invading your garden in the first place, and how to fight them if they’re already there.

Below is an image from the United States Department of Agriculture that highlights the areas which are at risk for Japanese beetle damage. Anyone within the states highlighted in green should be on the lookout for signs of Japanese beetles, even if your garden shows no current signs of their presence.

So, how can I tell if the pests I have are Japanese beetles?

The first, and most obvious, is if you can spot them in your garden. They’re typically half an inch long, and are shiny, with most of their bodies being green and copper colored. They’re rather slow moving, so it shouldn’t be hard to get a close-up look.

You can also look for signs that they’ve been feeding. In June or July through August, leaves and flowers that have become Japanese beetle food will look almost like lace from the many bites taken out. Outside of the hot summer months, dead grass can be a sign that their larvae have been feeding on roots in your lawn.

Well, how can I prevent them from eating up my garden?

The first step is to consider planting varieties of plants that they tend to shy away from and avoid planting things that they’re known to favor. Some plants that resist them well are: Boxwoods, burning-bushes, juniper, lilac, arborvitae, begonia, coral-bells, hosta, impatiens, lantanas, garlic, and more. This list is not exhaustive, but it should provide a great starting point! When planting something that’s known to be Japanese beetle food, try to plant it near things that they don’t like, for added protection.

They’re already damaging my plants! What can I do?

You have a handful of options when dealing with Japanese beetles, depending on how bad the infestation seems. Chemical treatments are an option, but first you should consider:

• Hand-removing any Japanese beetles you find. They’re slow movers, especially in the morning. Shaking them off leaves and into a bucket of soapy water is an easy way to kill them. Be sure to remove any damaged foliage from the plant after this, as it can sometimes attract more.
• Neem oil. This naturally derived oil can be sprayed on plants that have been damaged and will kill eggs that the beetle goes on to lay. However, it must be reapplied after rain and should not be used near bodies of water, as it can upset aquatic ecosystems.
• Nematodes. These are parasitic worms that feed on Japanese beetles, and they won’t harm your garden. Heterorhabditis bacteriophora is a common option for dealing with these pests and can often be found in local garden centers.
• Milky Spore. This is a bacterium that requires numerous applications over about two years but is highly effective at killing Japanese beetles and can remain effective for up to two decades once the application process is complete.
• Mechanical traps. These can be found at almost any garden center and are quite effective at controlling Japanese beetle populations that aren’t at ‘out of control’ levels. 

Finally,

• Insecticides. There are several chemical options for killing Japanese beetles if you wish to go this route. Because insecticides can have harmful unforeseen consequences, we recommend that anyone curious about this option first speak with an expert at their local garden center to find out what is approved and recommended in their area.

Unfortunately, it seems that Japanese beetles will always be a pest to watch out for in many areas of the United States. Pest control should always be a factor you consider in garden planning, but it should never stop you from creating the garden of your dreams. Keep trying out new prevention methods based on what seems right for your situation— and keep us in the loop on what works best!