How to use neem oil to kill japanese beetles

How to Identify Japanese Beetles

Japanese Beetles are ½ inch in length with metallic blue-green heads. They have copper-colored backs, tan wings, and small white hairs lining each side of the abdomen. Japanese beetles usually feed in small groups.

Table of Contents Show

How to Identify Japanese Beetles
Signs of Japanese Beetle Damage
DIY Neem Oil Insect Spray
How Does Neem Oil Work?
Neem Oil Insect Spray Recipe
Using Neem Oil Insecticide
Shopping List
How often should you spray neem oil for Japanese beetles?
How long does it take neem oil to kill Japanese beetles?
Will neem oil get rid of Japanese beetles?
How do you use neem to get rid of Japanese beetles?

Prior to becoming adult beetles in June, they are 1-inch-long, white, c-shaped grubs live in the soil and feed on the roots of many plants. Often, these grubs are a problem in lawns.

Once adults, they don’t live long but they are voracious. They attack plants in groups, which is why damage is so severe. Although the lifecycle of the adult Japanese beetle is barely 40 days, it can cover a lot of ground. Even if you succeed in controlling your Japanese beetle population, your neighbor’s Japanese beetles might come on over.

Photo Credit: Ohio State University. Japanese beetles cause leaves to appear skeletonized.

Signs of Japanese Beetle Damage

Japanese beetles feed on a wide variety of flowers and crops (the adult beetles attack more than 300 different kinds of plants), but in terms of garden plants, they are especially common on roses, as well as beans, grapes, and raspberries. Here’s what to look out for:

Skeletonized Leaves and Flowers

Japanese beetles chew leaf tissue from between the veins, leaving a lacy skeleton. You’ll know right away when you see leaves that are “skeletonized” (i.e., only have veins remaining). (Mexican Bean Beetles can also leave foliage skeletonized, though, so be sure to identify the beetle by their appearance as well.)

Japanese beetles are not usually far from damaged leaves, so inspect the plant thoroughly. Also keep an eye on the ground beneath the plant; the beetles may reflexively drop off the plant if disturbed.

Unhealthy, Brown Patches in Lawn

Japanese beetle grubs damage grass when overwintering in the soil, as they feast on the roots of lawn grasses and garden plants. This can cause brown patches of dead or dying grass to form in the lawn, which will pull up easily thanks to the weakened roots.

Ask any Minnesotan gardener, the number one destroyer of a vegetable garden is the Japanese beetle, an invasive insect species that attack the leaves of vegetable plants, berry bushes and vines, and fruit trees.

DIY Neem Oil Insect Spray

Neem oil is a natural pesticide made from the seeds of the tropical Neem tree. It's been used for hundreds of years to control insects and is not harmful to humans, bees, or pets. In fact, Neem oil is often used in cosmetics. The active ingredient in Neem oil is Azadirachtin.

How Does Neem Oil Work?

Neem oil is a bitter thick brown oil that has a slight garlic scent. When Japanese beetles eat the leaves that are coated in Neem oil, their voracious appetites are inhibited by the oil which causes the beetle to wither and die before they are able to mate.

I have also added essential oils to the Neem oil spray as they are natural insect repellents. The USDA conducted a study to determine which essential oil repel Japanese beetles and they found that peppermint and wintergreen were the most effective. Luckily, bees are not affected by either the peppermint or wintergreen essential oils.

Neem Oil Insect Spray Recipe

828 ml (28 FL oz) bottle (I use an empty Method bottle, rinsed out)

1 tsp Neem oil

25 drops peppermint essential oil

25 drops wintergreen essential oil

Squirt of liquid dish soap (I used Meyers)

Water, RO water preferably, but tap is OK

Fill your bottle 3/4 with water. Pour in Neem oil, essential oils, and dish soap. Put the top on and give the bottle a good shake. Then top the bottle with a bit more water so that there is only an inch left of air.

Using Neem Oil Insecticide

Shake the bottle often while spraying the leaves of your plants. Try to avoid spraying flowers heavily. Only spray in the morning or evening when the sun is less hot. I spray everyday as the active ingredient degrades in the sun within 24 hours.

Shopping List

I purchased all my ingredients from Amazon.

Neem Oil

Peppermint Essential Oil

Wintergreen Essential Oil

Meyers Dish Soap

I posted a tour of my garden so you can see the results of the auto watering systems.

Neem: A Pesticide That Is Also a Toothpaste! by University of Minnesota Extension

How often should you spray neem oil for Japanese beetles?

NEEM: An application of Neem Oil as soon as beetles are spotted can help diminish feeding. Apply every 7 days while beetles are feeding. To prevent leaf burn and to avoid hurting honeybees, spray Neem Oil late in the evening.

How long does it take neem oil to kill Japanese beetles?

Neem oil can kill Japanese beetles in as little as one hour if they are exposed to high concentrations of it, but it takes time for the treatment to work fully. The insects may die within minutes and larvae may take up to two hours before they die.

Will neem oil get rid of Japanese beetles?

Neem Oil Concentrate works on a wide variety of pests including Japanese beetles, aphids, mites, whiteflies, flea beetles and earwigs.

How do you use neem to get rid of Japanese beetles?

Foliar sprays are a topical solution using 4 teaspoons of clarified neem oil per gallon of water. Only apply the foliar spray at dusk or dawn. Soak every part of the plant, especially the undersides of leaves and any cracks or crevasses. The spray will dissipate after 45 minutes to an hour, leaving behind no residue.