Japanese beetles are a type of scarab beetles, and adult beetles are recognizable by their copper-colored forewings and green heads. Although these insects are fascinating to look at, seeing them in your garden could mean damage to your plants. Learning how to use neem oil for Japanese beetles is essential to protect your favorite plants from Japanese beetle damage.
Although native to Japan, adult Japanese beetles are not harmful pests in their homeland due to the presence of beneficial insects that act as natural predators.
In North America, without interference from predators, Japanese beetles are pests of around 300 plant species. Common host plants for Japanese beetles and their grubs include fruit trees, rose bushes, flowering plants, and even hardwood trees.
Japanese Beetle Control with Neem Oil
Many gardeners turn to natural pest control methods to control the Japanese beetle population. Attracting and using companion plants to protect your garden from beetles are effective forms of pest control; however, using neem oil as a natural pesticide is excellent for controlling beetle activity and reducing their numbers.
Neem oil is a cold-pressed vegetable oil from the neem tree. This oil is a natural insecticide that comes as crude oil with a high chemical compound level that has severe side effects on insects, including flea beetles and aphids.
What does Neem Oil Do to Beetles?
Neem oil is a powerful tool for any gardener, thanks to one of its most crucial compounds, azadirachtin. This chemical compound targets the hormone systems of insects, and after application to your plants, it discourages feeding.
Neem oil is an insect growth regulator (IGR), meaning that spraying insects with neem oil affects their growth. Adult beetles sprayed with neem oil struggle to mate and lay eggs, and Japanese beetle grubs may never advance to the next stage in their life cycle. As effective as neem oil at disrupting the feeding behavior of pests, does neem oil kill Japanese beetles?
Can You Use Neem Oil to Kill Japanese Beetles?
Although neem oil severely affects pests like Japanese beetles, it is not poisonous to them. Since it is not fatal to these bugs, it is impossible to use neem oil to kill Japanese beetles that reach the adult stage.
When you spray neem oil on Japanese beetles, the homemade insecticide will likely slide off their hard bodies with no lasting effects. The efficiency of neem oil comes from ingesting it, so it’s crucial to spray affected plants as soon as you notice beetle damage.
Despite not being fatal to adult beetles, neem oil is still considered a Japanese beetle killer because of its effectiveness against Japanese beetle larvae.
How to Use Neem Oil for Japanese Beetles
The best time for Japanese beetle control with neem oil is when you notice damage to your garden plants. Although it is an insecticide with the power to kill insects, many gardeners view neem oil as an antifeedant.
Neem oil is known for its garlicky smell that overwhelms insects’ senses and causes them to stay away from treated areas. Once you notice signs of Japanese beetle damage, treat your plants to prevent Japanese beetles from eating your plants.
Using a Neem Oil Foliar Spray
Foliar sprays are liquid treatments for plants that coat the leaves. This spray repels insects due to its strong smell, and insects like Japanese beetles that feed on the leaves of plants are affected by the compounds in neem oil. You can also get rid of cucumber beetles and use the spray to treat squash bugs and aphids the same way.
Mix your water and soap in the sprayer first before adding neem oil. Combine well and spray your plants at dawn or dusk. Treating at the correct times of the day reduces the risk of spraying any beneficial insects with neem oil. Spritz your plants every other day for two weeks or until all signs of Japanese beetles are gone. Neem oil does kill aphids too, as well as other annoying insect pests.
Take care not to spray any flowers. Neem oil does not harm bees as they are only concerned with pollination of the flowers and not the leaves. However, if flowers are sprayed with neem oil, it will kill the bees and butterflies, too.
Neem Oil Soak for Grubs
After mating, Japanese beetles lay their eggs in clusters on the soil’s surface. These eggs hatch within two weeks and mature by feeding on grass roots and the root systems of any nearby vegetable crops. These larvae become grubs that feed on coarser roots and risk causing extensive damage to pastures if left unchecked.
Because larvae hibernate and grow in the soil, targeting the soil in your garden or orchard is the best way to stop a Japanese beetle infestation. To eradicate grubs with neem oil, create a soak with water, neem oil, and an emulsifier like dish soap.
Mix your soap and water to reduce the water’s surface tension before adding your oil. Measure out one or two cups to spread around your plants. Use more of the drench around shrubs and trees as needed. This soak poisons larvae in the soil, suffocating them and preventing them from becoming adults.
Alternatives to Neem Oil
Due to the size of Japanese beetles, picking them off your plants is one option for reducing their numbers. Carry a bucket of soapy water to the garden and drop any beetles into the water to kill them. Dispose of the dead beetles outside and regularly check your plants for more beetles.
Milky Spore is a commercial item that uses bacteria to kill grubs before they reach adulthood. Like beneficial nematodes, this bacteria is applied to the soil and left to work long-term against beetle larvae.
Food-grade diatomaceous earth (DE) is a white powder made from the bodies of diatoms. Although food-grade diatomaceous earth is safe around humans and pets, the sharp edges of the diatoms cut into soft-bodied insects to kill them. Sprinkle diatomaceous earth across the soil in your garden to kill emerging larvae before they reach the adult stage.
Companion planting benefits your garden by providing adjacent plants with nutrients and sometimes shade; however, plant geraniums to deal with Japanese beetles.
Geraniums contain a compound that causes a form of paralysis for Japanese beetles. Although it is not fatal, you can collect their bodies while paralyzed. Beetles are open to attacks from prey during this time as well.
Making a Japanese Beetle Trap
To draw Japanese beetles away from host plants, consider using a simple water trap and a cup of fruit cocktail. Fruit cocktail purchased from the store contains a lot of sugar; the smell attracts Japanese beetles.
Fill a container with water and place a brick in the center. Leave an opened cup of fruit cocktail on the brick. As the cocktail ferments in the sun, beetles drawn to the sweet smell drown in the surrounding water.
Although using neem oil to kill Japanese beetles is not a foolproof method of pest control, there are many other innovative ways to deal with a beetle issue in your garden. Use sprays and neem oil soaks to reduce the number of Japanese beetles in your garden to protect your plants.
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