DIY Neem Oil Insecticide For Japanese Beetles

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. 

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Please go to my post, Gardening With a Drip Auto Watering System, to learn about how I put together my drip irrigation system.

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

Organic Pesticides by University of Wisconsin, Madison, Master Gardeners

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