The Hort Report: Combine Neem Oil, liquid dish soap to help in fight against Japanese beetles


Few garden pests match the destructive power of Japanese beetles. | Photo courtesy of Wikipedia

The Summer Solstice — the first day of summer — was June 20. The daylight hours we have each day will decrease until the Winter Solstice on the first day of winter on Dec. 21.

The weather we have been having the past few days reminds me of 2023. The hot dry wind and lack of rain is beginning to show on vegetables and flowers. 

You need to be watering everything. Water early in the morning or after 6 p.m. to get the most from the water you are using. 

Mulching will help conserve water and keep weeds down. Doing this also will help conserve water.

I have seen a few Japanese beetles in the past few days. Few garden pests match the destructive power of Japanese beetles. In their mature form, they decimate gardens, leaving skeletonized leaves and weakened plants behind. In their immature stage, when they’re commonly called grubs, they feast on tender grassroots, leaving brown, dying lawns in their wake.

I want to give you things to do to fight them.

Decide on organic or regular pesticide spray. Using regular insecticide sprays will kill Japanese beetles but can kill beneficial insects too. You need to spray all the foliage of plants, trees, bushes, shrubs and grass. 

Using Neem Oil as a spray to fight Japanese beetles is a very safe insecticide to use. When sprayed on foliage, it causes them to stop feeding. They aren’t able to reproduce once they get Neem Oil into their system.

You also can spray the grass and soil with Neem Oil. Neem Oil can kill Japanese beetles in their adult, larva and grub stages of life. 

Mix four teaspoons of Neem Oil to one gallon of water. Add 3-4 drops of liquid dish soap to the mix. This will help the mix adhere to all the foliage you spray and the Japanese beetles. Once the spray is on the foliage, it will stay there as a deterrent to all new Japanese Beetles. Spray weekly to help kill Japanese beetles. Spray after any rains or watering of foliage.

I plan on using both types of spray mixes in different ways in the coming days. The regular type of insecticide may stay on the soil and grass longer following rain.

The Neem Oil mix will be safer to use on all the foliage of plants that are producing food to eat. I will see how this works and let you know. 

You can hand-pick Japanese Beetles off foliage. Start when you first begin to see them. I take a one-gallon pail of water and start to put them in it. They drown, and once I get it almost full. I pour it into a five-gallon bucket. Cover this bucket. Once the bucket is full, I pour the bucket of Japanese beetles and water into a creek by my house.  

I hand-pick early in the morning or late in the day about dark. This is when the Japanese Beetle is just sitting there resting. I sometimes can just shake a leaf, and they fall into the pail. 

Try not to use traps. Japanese beetle traps attract them to the trap’s bag with bait that smells. In years past, I have put out traps. Each night, I would dump the trap bags into five-gallon buckets with water in them. 

The first year, I dumped two buckets a day for more than 25 days in a row. The next year, it was about two buckets a week. This year I hope I don’t need any traps. If I do, I will place them far away from my fruit trees, grapes and berries. Traps will multiply the number of beetles coming to your yard, so don’t use them if possible.

I appreciate all your questions in the past and look forward to them in the future. Please keep them coming. Call me at 573-588-2040 at Shelby County Implement in Shelbina, Mo. Email me at or visit on Facebook at Greenwell’s Greenhouse Group. Best yet, just come out and see me or stop me anytime you see me. I enjoy doing this the most.

Pat Greenwell is the owner of Shelby County Implement in Shelbina, Mo. He was a high school agriculture teacher for 11 years. He has taught adult vocational agriculture since 1987. He also is a research assistant at the Truman State University Ag Department Farm. 

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