Summer is finally here which means vacations and warmer temperatures. As the summer heat increases, so do the number of insects. One of the most troublesome insects in the eastern United States is the Japanese beetle. The Japanese beetle causes major damage to urban landscapes.
The adult Japanese beetle is 7/16-inches long, metallic green, with copper-brown wing covers. A row of white tufts (spots) of hair projects under the wing covers on each side of the body.
Japanese beetles were accidentally introduced into New Jersey in 1961. Until that time, this insect was only found in Japan where it is not a major pest. The eastern US provides a very favorable climate, large areas of turf and pasture grass for developing grubs, hundreds of species of plants on which adults can feed, and no effective natural enemies. The beetles have thrived under the perfect conditions and have steadily increased populations and expanded westward. The geographic range is north to Ontario and Minnesota, west to Iowa, Missouri and Arkansas and south to Georgia and Alabama.
The life cycle of a Japanese beetle is as follows; the adults emerge from the ground and begin to feed on plants in late June. Activity is the most intense over a 4 to 6 week period and then the beetles gradually begin to die off. Individual beetles live for 30 to 45 days. Egg laying beings soon after the adults emerge from the ground and mate. Females leave the plants in the afternoon, to burrow 2 to 3 inches into the soil in a suitable area and lay their eggs which can consist of about 40 to 60 eggs during their life. The developing beetles spend the next 10 months in the soil as white grubs. The grubs grow quickly and by late August they are almost full size, about 1 inch long. The grubs feed on roots of living plants, doing the most damage in good quality turf in home lawns, golf courses, parks, and cemeteries. They can live in any soil in which plants can live.
Japanese beetles overwinter in the grub stage. When the soil cools to about 60°F in the fall, the grubs begin to move deeper. Most live through the winter 2 to 6 inches below the soil surface, but some will go as deep at 8 to 10 inches. They become inactive when the soil temperature falls to about 50°F. When the soil temperature climbs above 50°F in the spring, the grubs begin to move up into the root zone. Following a period of feeding on roots for about 4 to 6 weeks, the grubs mature and molt to pupae in the soil and remain there until they emerge as adults.
The adults feed on nearly 300 different host plants. Adults feed during the day, favoring hot weather and plants growing with full sun exposure. They usually feed in groups, starting at the top of the plant and working downward. They feed on the upper surface of foliage, chewing out tissue between the veins. This gives the leaf a lacelike or skeletonized appearance. A single beetle does not eat much; it is group feeding by many beetles that result in severe damage.
Landscape plants likely to be attacked by Japanese Beetles
Rose-of Sharon, Shrub Althea
Flowering crabapple, apple
Cherry, black cherry, plum, peach, etc.
Japanese beetles can be managed by a few methods. The first method is by using beetle traps. The traps lure the beetles into a container where they will die. There are 2 types of traps. One type of trap utilizes a floral lure as an attractant which is used in The Japanese Beetle Trap. The other trap employs a dual attractant of floral lure plus a synthetic sex attractant which is used in Xpando Japanese Beetle Trap and the Beetle Bagger. If using a trap make sure to place it away from susceptible host plants; otherwise, more Japanese beetles will be attracted to the host plants that you wish to protect.
Another option is to use an insecticidal spray that will kill the adults off of the host plants once you see them. This would include Beetle Killer, Japanese Beetle Killer and Captain Jack’s Deadbug Brew. For smaller plantings, or when beetle numbers are low, you can remove the beetles by hand. This is done by picking them off of the plant and placing them into a bucket of soapy water, where they will drown.
The last option is to kill the grubs in your lawn by using either Grub Killer Plus or Grub Beater. This is a great option if you have grub damage in your lawn. This method only works on grubs. Adults have wings and can travel to find food. Just because you have adult Japanese beetles doesn’t mean that you have a grub issue. Before you choose which option is best for you, you should evaluate what life cycle stage you are having issues with and use the appropriate method.
Commercial-grade control options include Mallet for systemic control and Tempo for quick kill of adults.
Japanese beetles have been in the U.S. for over 50 years and have spread quickly across the country, but they don’t have to ruin your beautiful landscape this summer. Make sure you keep an eye out for the metallic green, with copper-brown wing covers in your landscape so you can attack this insect effectively.