Rue plants are native to Europe, but they are cultivated in the United States. The flowering shrub has an unpleasant aroma, which keeps away insects. One insect, in particular, is the Japanese beetle. The Japanese beetle destroys leaves and roots of more than 300 species of plants, but they will not go near the rue plant.
The rue plant, or Ruta graveolens, is an evergreen shrub that produces small, yellow flowers. The smell comes from the fresh leaves. During the Middle Ages, it was considered a "a powerful defense against witches," according to Botanical.com. According to Herbs 2000, the wealthy carried rue in bouquets to "ward off the lice of vagabonds and beggars." As an herb, rue has been used to treat insect bites, cramps and even multiple sclerosis.
The rue plant has attractive blue-green foliage, which grows in a mound. Gardeners use it as a low hedge, often in outside pots and in rock gardens. It does well in sandy soils and hot, dry sites. It grows best in zones 4 through 9. Rue attracts butterflies, but it repels cats, as well as the Japanese beetle. It is a good companion for roses and raspberries because Japanese beetles are attracted to those plants.
Harry B. Weiss and Edgar L. Dickerson discovered Japanese beetles in the United States in August of 1916. The beetles were on plants at a nursery near Riverton, N.J. By 1921, the Japanese beetles had infected more than 213 square mile of New Jersey. According to the USDA, Japanese beetles are now a serious pest problem in states east of the Mississippi River as well as in Iowa and Missouri. The beetles continue to spread to western and southern states.
The adult Japanese beetle is a half-inch long with a shiny, green body and copper wings. The beetle feeds on foliage of plants, leaving the plants with a skeleton appearance. Not only do the adult beetles do damage, but the insects' larvae or grubs damage the plant's root system, making it difficult for the plant to draw water and soil nutrients. Since these beetles migrate, they are drawn to areas where other beetles are located.
Managing Japanese Beetles
It is impossible to eliminate the Japanese beetle, but it is possible to cut down the population and decrease the damage to plants. Chemical pesticides may be used, but they are toxic and can cause serious problems for people and wildlife if they are not used properly. The rue plant is a natural way to deter the Japanese beetle. Plant rue near any plants that attract Japanese beetles. Full sun and well-drained soil are best for the rue plant. Because it is self-seeding, deadhead to stop the plant from spreading.