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Controlling Japanese beetles requires a two-pronged attack

Posted: July 14, 2013 - 12:01am

Every year, insects arrive in our gardens and landscapes to devour everything in sight. Usually, the Japanese beetle makes its presence known earlier in the spring, but the extension office received a lot of calls about them last week.

The Japanese beetle, Popillia japonica Newman, is a widespread and destructive pest of turf, landscape and ornamental plants. It is a pest of several fruit, garden, and field crops, and feeds on more than 300 plant species. Adult Japanese beetles feed on foliage, flowers, and fruits.

The two major ornamentals attacked in our area are roses and crape myrtles. Other plants they eat are hibiscus, apples, pears, plums and many vegetables, especially beans. The Japanese beetle is the most widespread pest of turf grass and costs the turf and ornamental industry approximately $450 million each year in management alone (Potter and Held, 2002).

Japanese beetles were introduced into the United States in 1916 in New Jersey. Since then, they have spread to all the northern states, mid-western states, and to the southern states. In Georgia, they are found north of the fall line.

Japanese beetles are easy to identify because they are bright metallic green with coppery brown forewings that reach almost to the tip of the abdomen. There is a row of five white spots along the side of the abdomen and a pair of white spots on the top of the last abdominal segment. The spots help distinguish them from other beetles such as the Green June beetle.

To control Japanese beetles, we must understand their life cycle. There is one generation per year. The adults emerge in late May or June and can be active until July. The adults will live four to six weeks with the females laying eggs during this time. The eggs hatch in two to three weeks into the larval stage. The larval stage, which is a white grub, will become mature grubs by early fall. The grubs over-winter in the soil, and in the spring they pupate and become adults. Then the cycle begins again.

Both the adult stage and the grub stage must be controlled to eradicate the problem. Adult beetles can be removed by hand from the garden. To control the grubs, there are two times of the year when treatment is most effective. The first is late August through September, and the other is March. The grubs are closest to the soil surface at these times. There is an organic control option as well as insecticides. The organic option is a fungus called milky spore, Bacillus popilliae. The organic treatment is available in stores or online. Additionally, there are several insecticides to control the grub stage. Examples include pyrethroid products such as cyfluthrin (Tempo, Bayer Advanced Lawn & Garden Multi-Insect Killer), bifenthrin (TalstarOne, Onyx), deltamethrin (Deltagard), lambda cyhalothrin (Scimitar, Spectracide Triazicide), esfenvalerate (Ortho Bug-B-Gon Garden & Landscape Insect Killer) and permethrin (Spectracide Bug Stop Multi-Purpose Insect Control Concentrate and other brands). The pyrethroid products generally provide two to three weeks protection of plant foliage. Read and follow the labels on all pesticide products.

There is an additional control option that is not recommended. Japanese beetle traps use pheromones to lure the beetle into the trap. However, more beetles might be drawn into the yard because of the pheromones emitted from the trap. The beetles can fly in from as far as a quarter of a mile away.

An early control program is the best means for preventing these unwanted guests.

If they are present now, the best method is to remove visible adults and treat for grubs in the fall.

TRIPP WILLIAMS, COLUMBIA COUNTY’S AGRICULTURE AND NATURAL RESOURCE EXTENSION AGENT, CAN BE REACHED AT (706) 541-4011, OR TRIPPJ@UGA.EDU.

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