Choose the Right Plants to Have Fewer Pests!
They are devouring my clematis, climbing hydrangea and I am finding them on my whirling butterfly guara plant (Bee blossom) I found eliminating most of the plants/trees that they love helped to lessen the amount of beetles. I use a hand sprayer with a few tbsp of blue dawn dish soap, and some powdered garlic, fill with water...spray the plants liberally twice a day. It doesn't harm the plants but the beetles go belly up and drop to the ground within minutes of spraying. They also fly out of there fast! *you can omit the garlic, it's the blue dawn that seems to work. I had hundreds on my climbing hydrangea and after 3 days of spraying, I found 2 today. I just wish I had started spraying soap solution before the damage was done....next year I will proactively spray when I see the first beetle and perhaps save the foliage from so much damage.
Try sevin dust or a pump sprayer with liquid sevin diluted and Japanese beetles drop like crazy. As far as the larvae, spray your yard in August and September to start killing the hatch. I also have heard the arguments about hanging traps in my yard and I will take my chances by tying off a bag every few weeks and killing 3-4 thousand beetles, what a joy. That is a lot males not fertilizing eggs. There are a few websites that have scheduled spray times and what to use at the right time for your area.
The nursery told me NOT to squash Japanese Beetles as that releases their pheromones which attracts more beetles to your yard. Traps, I was told they would be happy to take my money but not to put any in my yard as they attract more beetles to your yard. If hand picking Japanese Beetles drop them in a container of water & dish soap.
Ditto on someone who mentioned basil below. Unfortunately for us it seems to be one of their favorites. That and cilantro.
Gosh I hate them.... But at over 85 I can'tchase them Poured about a cup into each container and they left!
Milky Spore and Praying Mantis!!! One application of Milky Spore lasts 10 to 20 years. Praying Mantis are carnivorous and are fun to watch.
Tulle netting is very effective at protecting plants. I sew a 20-foot long box out of tulle and lay it over an arbor made from pvc pipes. This keeps the beetles from feasting on my grape vines. I have also made another box to protect my raspberries. This box is supported by T-posts with old tennis balls over the tops. The posts are spaced about 4-5 feet apart. The only weakness I have found with tulle is that after 2 or 3 years, it succumbs to the effects of the sun and rain and I have to replace it.
Buy a thin net fabric called tulle at any fabric store - it's very cheap. It is a netting with very small holes. Cover your plants with it - it lets in light, water but not the beetles. I use it on all my potted flowers that they are attracted to. Have to keep it on for about 6 weeks until they are gone but it works & doesn't poison bees, butterflies etc.
Use Neem oil for your Japanese beetle infestation. Mix a spray bottle with a tablespoon of neem oil, dish soap (teaspoon) and water. Spray all your leaves front and back every day in the morning or at dusk. When they eat these, it will kill their reproductive system and can't lay eggs in your yard. But you will also have to treat your lawn with milky spore and nematodes to kill the larva. There is no instant kill, they will always come back, but these things will help not kill your grass and won't be harmful to the environment, bees or other animals that eat the bugs.