How to prevent Japanese beetle spread
Insects occupy various roles in the landscape. They can be food for wildlife, sources of human food, pollinators, waste decomposers, and natural and biological garden protectors.
Some insects can be considered pests. Pests are organisms with characteristic that humans determine to be harmful or unwanted and cause extensive damage to food sources and habitats. One such insect pest is the invasive Japanese beetle (Popillia japonica).
The Japanese beetle chews off the desired plant part, resulting in plant injury. These injuries add up to extensive damage among ornamental and fruit trees, shrubs, lawns, crops and flowers throughout the eastern United States. Estimates are that in the United States over $460 million a year is spent to control Japanese beetle infestations.
The Japanese beetle is a native of Japan, where it is not considered a pest. Ecological safeguards are in place that prevent the beetle from emerging as a threat. Some plants in Japan have developed chemicals that deter the beetle from consuming its parts. There is a parasitic wasp that lays its eggs on the beetle, then the emerging young eat the beetle.
The Japanese beetle was first documented in the United States in a nursery near Riverton, N.J., in 1916. The beetle larvae are thought to have entered the United States in a shipment of Iris bulbs prior to 1912 before there was inspection of goods entering the country.
The Japanese beetle life cycle is completed over a one-year period and is called a metamorphosis. The beetle's eggs are laid individually or in small clusters near the soil's surface.
An adult female can lay 40 to 60 eggs in her lifetime. Egg laying begins soon after the adult emerges from the ground. Within two weeks the eggs hatch, and the larvae begin feeding on roots and other organic matter.
As the larvae mature, they evolve into C-shaped white grubs. Grubs are mobile and consume coarser roots, causing extensive damage to grass and plant roots. Grubs feed in August through September.
By mid-October, grubs move 6 to 18 inches into the soil and remain inactive until spring. In early April, the grubs return to the surface and briefly feed on roots; in lawns, brown patches can indicate Japanese beetle damage when grubs eat grass roots. During late May they stop feeding, and in June they emerge as adults.
The adult Japanese beetle has a metallic green body with copper-colored wing covers and white tufts of hair.
As soon as they emerge as adults, the beetles begin feeding, mating and laying eggs. The adult beetles release pheromones, chemical substances used by insects and organisms to communicate with and attract others.The first adults to appear act as scouts and call entire populations of new eaters to feast on plants. Adult beetles can fly 5 miles in search of mates and food, feeding on over 300 host plants. These plants include roses and grapes. Adults are active for about two months, appearing in June, increasing their activity late June through August or September, dying off in early fall.Plant damage from the Japanese beetle is obvious. The eaten leaves appear like “skeletons,” as the beetles eat the leaf material with the leaf veins intact. Beetles usually are found in clusters or groups as they devour plants. Their active feeding times are in the heat of the afternoon.The control of adult Japanese beetles is challenging and includes a variety of horticultural methods.Remove as many beetles as possible early in the summer to prevent them from multiplying. Hand removal is recommended.Fill a small bucket with soapy water and don garden gloves. Pick or shake the beetles into the soapy water. Use this method early in the morning before they become active in the heat.
Small hand vacuums dedicated to sweeping the beetles off of plants and trapping them in the hand vacuum is another way of collecting and disposing of the beetles.Japanese beetle traps are another effective method for controlling their population.The traps work by using artificial pheromones to attract the beetles into the trap.While the traps are effective, they can lure more beetles into the garden. Site the trap away from host plants and place a bucket of water underneath the bag to catch stray beetles.Another option is to grow plants resistant to Japanese beetles. Some of these plants are catnip, larkspur, garlic, onions, rue, marigolds, tansy, white chrysanthemum, and white geranium.Biological and chemical control of grubs halts the beetle's lifecycle. Penn State Extension (https://extension.psu.edu/white-grubs-may-june-and-japanese-beetles) offers specific suggestions for biological and chemical control options for grubs.Obtain professional guidance prior to using insecticides and be sure to follow the manufacture's label directions for use.Penn State Extension offers additional information on how to control grubs, including Japanese beetle grubs (https://extension.psu.edu/white-grubs-underground-marauders-in-turf); and how to manage Japanese beetles on ornamental plants (https://extension.psu.edu/japanese-beetle-control-on-ornamental-plants), home fruit brambles (https://extension.psu.edu/japanese-beetles-in-brambles-in-the-home-fruit-planting) and home peach trees (https://extension.psu.edu/japanese-beetles-in-home-fruit-plantings-of-peaches).Japanese beetles are a serious agricultural threat to home and commercial gardeners. Remain astute to their life cycle and act diligently to prevent their spread.If you have questions about Japanese beetles, call the Master Gardener Garden Hotline at 724-287-4761, Ext. 7, or email the Master Gardeners at butlermg@psu.edu.Susan McGarvey is a Butler County Master Gardener.
