Japanese beetles came into the United States in 1916, according to the United States Department of Agriculture. They aren't a problem in Japan because natural predators keep their numbers down. The lack of predators in the U.S. has allowed the Japanese beetle population to grow. These pests ravage the fruit, as well as the leaves, of fruit trees, decorative trees, vegetables, field crops, shrubs and vines. There are chemicals you can buy and use to kill Japanese beetles. There are natural methods you can use instead, such as making a baited trap.
Pour 1 cup of water into a medium-size bowl. Add 1/4 of a cup sugar and a package of yeast. Stir well with a spoon until both ingredients are dissolved. Peel the banana and discard the peel. Mash the ripened banana with a fork in a separate bowl.
Add the mashed banana to the sugar/yeast mixture. Mix it in well, according to Golden Harvest Organics. To kill Japanese beetles in a natural manner, pour the mixture into a gallon milk jug.
Set the gallon jug in a place where you have seen a lot of Japanese beetles. As the mixture ferments, the odor will attract beetles. They'll crawl into the jug, but won't be able to leave, and will die.