How can you get rid of Japanese beetles in your yard? Say sayonara in various ways, including hand picking, exclusion, habitat modification, or pesticides. If your infestation is more than you can handle on your own, enlist the help of a pest control pro.
What are Japanese Beetles?
Native to their namesake country, Japanese beetles (scientific name Popillia japonica) were accidentally introduced to the United States in 1916 by way of infested, imported plants arriving in New Jersey.
Sporting metallic green heads, copper-colored wing covers, and oval-shaped bodies, adult Japanese beetles grow to about half an inch long. Mainly active in July and August, these garden and lawn pests spend their time mating and feeding on 300-plus species of trees, shrubs, flowers, and grass.
Telltale signs of adult Japanese beetle damage include “skeletonized leaves” and holes in flower petals. Indications of damage by Japanese beetle grubs include brown patches on lawn grass.
After mating, female beetles lay eggs 1 to 3 inches underground, according to the University of Minnesota extension. They can lay up to 60 eggs over the course of their two-month adult lifespan.
Eggs take about two weeks to hatch, and the emerging white grubs remain underground all fall, winter, and spring, feeding on soil and grass roots. Once they reach maturation in summer, these new adult Japanese beetles come out of the ground and fly for miles, if necessary, in search of food.
The Japanese beetle life cycle repeats year after year, but, you can combat these pests at every stage by taking a few proactive measures.
How to Get Rid of Adult Japanese Beetles Naturally
The key is to begin controlling adult Japanese beetle populations as soon as they begin emerging from the ground between May and June.
1. Physical removal
For homeowners with smaller yards and fewer plants, hand picking adult beetles from affected flowers, trees, and shrubs may be the most efficient, cost-effective option. Hand picking helps inhibit leaf and petal damage, which in turn, prevents plants from emitting chemicals signaling they’re a good food source.
Target adult Japanese beetles during the early morning or evening. This is when they’re most sluggish and easiest to remove, suggests the University of Minnesota extension. As you pluck individual beetles from plants, drop them into a bucket of soapy water to kill them.
While you can’t keep these pests from coming into your yard, you can protect your plants from the damage they cause. Row covers are tunnel-shaped and fit over the top of plants to block Japanese beetles (and other bugs) from getting to them. Purchase row covers or simple netting from your local store, or build your own.
Note: Wait for plants to finish blooming before covering them up, so you don’t prevent pollinators from reaching them.
Japanese beetle traps work by releasing both floral scents and female beetle pheromones to attract these pests.
And while the number of dead beetles caught — thousands per day! — seems impressive, the truth is, these lures attract way more Japanese beetles into your yard than they catch and kill.
This, paired with the fact that traps alone will not actually help reduce the population of Japanese beetles, is why experts recommend against using traps as a control measure.
4. Habitat modification
Selecting plants that are resistant to Japanese beetle attacks can help control an infestation.
According to the United States Department of Agriculture, red maples, boxwoods, dogwoods, holly, and pine are just a few of the trees and shrubs Japanese beetles avoid. Some types of crabapple trees also show resistance.
On the flower front, Japanese beetles avoid forget-me-nots, coral bells, chrysanthemums, hosta, and impatiens. Geraniums may also aid in getting rid of Japanese beetles by paralyzing them, leaving them open to attacks from predators.
How to Get Rid of Japanese Beetles Chemically
If natural methods aren’t providing the results you need, you may want to consider insecticides. Here’s how to safely use chemical controls to get rid of Japanese beetle adults and grubs.
1. Neem oil
For decades, neem oil has proved a successful repellent of adult Japanese beetles. A low-risk pesticide that won’t harm beneficial insects, neem oil is available online or at your local hardware store.
If you’d rather DIY it, you can create a spray with a few drops of neem oil, a few drops of dish soap, and a gallon of water. Pour the mixture into a spray bottle and apply it to affected plants.
2. Pesticide sprays
Pesticides made with pyrethrins will kill adult beetles on contact only.
For chemicals with a residual effect, the University of Minnesota extension suggests products made with chlorantraniliprole, pyrethroids, or carbaryl. Depending on the ingredient, these options can provide around two to four weeks of plant protection.
Soil drench and tree trunk spray and injections should only be done by a pest control pro. These types of pesticides work by moving through a plant’s tissues.
How to Get Rid of Japanese Beetle Larvae Naturally
Control measures for adult beetles and grubs differ greatly. To get rid of Japanese beetles at the grub stage, try the following pesticide-free methods:
1. Natural predators
This method works on both adult beetles and grubs, depending on the predator used.
For eliminating grubs in your lawn, the USDA recommends unleashing the grub parasite tiphia vernalis. A tiny, parasitic wasp, tiphia vernalis burrows in the soil after mating, paralyzes grubs by stinging them, and then lays its eggs on them. When the eggs hatch, the emerging wasp eats the grub.
Isotecheta aldrichi is a parasitic fly that attacks adult Japanese beetles. After mating, these flies lay their eggs on the adult Japanese beetle’s thorax. When the eggs hatch, the maggots drill into the beetle’s body, killing it. These flies reduce Japanese beetle populations by killing adults before they have a chance to reproduce.
Note: Neither of these natural predators is commercially available, but your local extension office can let you know if you can find them in your area. Then, you can plant food sources that will attract these parasites.
Nematodes are another natural predator of Japanese beetle grubs. According to the USDA, “Upon penetrating a grub, the nematode inoculates it with the bacteria. The bacteria reproduce quickly, feeding on the grub tissue.” The nematode eats this bacteria, ultimately killing the grub.”
Pro tip: Buy the Heterorhabditis bacteriophora nematode online and apply to your lawn to battle Japanese beetles.
2. Milky Spore
Milky spore is a bacterium registered for use against Japanese beetle grubs, but not everyone agrees on its effectiveness. The USDA recommends using milky spore to fight Japanese beetles on turf grasses, but some experts say there’s not enough evidence to support its effectiveness of milky spore.
Milky spore works when grubs in the soil ingest it, causing the bacteria to multiply in the grub’s body. The bacterial buildup causes grubs to take on a “milky” appearance, ultimately dying and releasing 1 billion to 2 billion spores back into the soil.
Japanese Beetles: Other Things You Should Know
Are Japanese beetles lethal to plants?
However, if there’s a big enough population feeding on large amounts of leaves, the loss of chlorophyll and foliage can severely stress the tree and open it up to secondary diseases that can lead to death.
As for lawns, Michigan State University‘s extension recommends irrigating lawns in fall and spring to prevent turf damage and loss. Well-watered grasses can tolerate the presence of grubs better.
Generally, healthy plants are able to tolerate minimal damage, so be sure to keep yours watered, pruned, and nourished.
Do Japanese beetles bite?
While harmful to flowers, trees, shrubs, and grasses, Japanese beetles do not bite humans or pets.
What are Japanese beetles’ favorite food sources?
While these insects will feed on more than 300 types of plants, Japanese beetles are more likely to feast on Japanese maple trees, roses, elms, cherries, plums, peaches, raspberries, and grapes.
When to Call Pest Control Pros
If your Japanese beetle infestation is severe, it could weaken lawn grasses, trees, shrubs, and flowers so much that they die of secondary causes. To avoid this fate, call in your local pest control professionals.
First, these experts will confirm your problem is truly Japanese beetles. Then, they’ll implement an integrated pest management approach, blending biological, cultural, and chemical control methods.