An infestation of Japanese beetles can quickly ruin your carefully tended backyard. Japanese beetles appear during the summer and eat leaves and flowers of many types of plants, shrubs, trees and vegetables. White beetle grubs feed on the roots of grasses, resulting in brown patches in your yard. Controlling your Japanese beetle problem involves killing mature beetles and destroying beetle grubs before they can become adult beetles. While pesticides can be used to kill Japanese beetles, other less toxic options are also available.
Place milky spore powder on your lawn to kill grubs. Apply 1 tsp every 4 feet and then water your lawn lightly to allow penetration of the powder into the soil. After infected grubs die, they release milky spores into the soil, providing long-term protection against beetle infestations.
Buy microscopic roundworms, called nematodes, to kill grubs. Nematodes search for grubs and inoculate them with a bacterium that eventually kills them. Mix nematodes with water, according to manufacturer instructions, and use a spray bottle or an insecticide sprayer to apply nematodes to your lawn.
Use insecticides on soil and plants to kill both grubs and adult Japanese beetles. Use plant-specific insecticide sprays or granules during the summer. Usage instructions vary depending on the type of grass, plant, tree or shrub. Follow manufacturer's instructions when using insecticide.
Pick adult beetles from leave and flowers. Plan to pick beetles in the late evening or early morning when they will be less active. Place the beetles in a solution of soapy water to kill them.
Buy traps to kill Japanese beetles. Place traps far from infested areas. Traps contain pheromones that attract the beetles. Placing them next to already infested areas may worsen the problem.
Planting shrubs and plants that Japanese beetles don't like can help keep the beetles out of your yard. The list of plants that Japanese beetles don't feed on includes buttercups, arbor vitae, daisies, forsythia, lilacs, red and white oak trees, red or silver maple trees, violets and begonias. Determine if you have Japanese beetle grubs by digging up a section of dying or dead grass. Mature Japanese beetle grubs are white, approximately 1 1/4 inches in length and curl up into a "C" shape if you poke them with an object. If you plan to use traps to kill Japanese beetles, ask your neighbours to also use the traps. Ohio State University reports that trap use is most effective when everyone in the neighbourhood uses the traps.
Don't expect immediate results if you use milky spore powder to kill grubs in your lawn. It usually takes two or three years until the spore count is high enough to be effective against the grubs.