Japanese beetles (Popillia japonica) are like small insect gems that shine in the light. In fact, in Mexico, Macquech brooches which incorporate the living beetles covered in small gems are worn as jewelry. This kind of use of beautiful insects as personal accessories came from an ancient Mayan tradition. However, Japanese beetles are best known as major agricultural pests. One American who recently tried to return to the U.S. wearing her brooch, was detained by the U.S. Customs.

“At the U.S.-Mexican border a bug decorated with jewels is still a bug…It may be restrained and openly displayed–as in anchored and chained to a woman’s sweater–but it is still classified as a pest.”

Damage Caused by Japanese Beetles:

Omaha Japanese beetles do enormous damage to gardens, lawns, and farm crops. A wide range of plants are attacked by the adults and the larvae. The 300 kinds of plants include small fruits, tree fruits, truck and garden crops, ornamental shrubs, vines and trees. Soft fruits like grapes, berries, and stone fruits can be completely consumed by the insects. The larvae eat the roots of a number of plants, but grasses are favored. The larvae collect in numbers and will cause bare patches. According to the California Department of Food and Agriculture (PDF). The potential loss to the fruit crop in California was more than $6.2 billion in 2007.

Experts rate the Japanese beetle as,

“…probably the most devastating pest of urban landscape plants in the eastern United States.”

One beetle can’t really do much damage, but the adult insects swarm over the upper surfaces of foliage, chewing out the tissue between the veins so that the plant can not sustain itself. The plant is left with skeleton-looking leaves. Whole rose petals are consumed. Swarms of the beetles consume the corn silk so that the corn plant can’t form kernels.

Arrival and Distribution:

The larva of this insect first appeared at a nursery in Riverton, New Jersey, entering the United States in a shipment of iris bulbs from Japan, sometime prior to 1912, when inspections began. The insect was never considered a pest in Japan. The first Japanese beetles arrived in Canada via Yarmouth, Nova Scotia by ferry from Maine in 1939. Now, as of 2015, only nine western US states are considered free of Japanese beetles.

It took 105 years for the population of Japanese beetles to make it across the U.S. continent and appear in west coast airports and agricultural areas outside of Portland, Oregon. Japanese beetles have travelled eastward across the Atlantic ocean too, making an appearance in the Azores Islands in the 1970s and in mainland Europe, near Milan, Italy in 2014.

Life Cycle:

Fertile females leave the plants they are feeding on in the afternoon. They burrow 2 or 3 inches into the soil and deposit eggs, a total of 40 to 60 eggs over their life span. Eventually white grubs emerge to spend the next 10 months living in the soil and feasting on plant roots. They are happiest in well-groom fields of grass, but they can survive in almost any soil where plants live. Irrigated lawns that are kept moist, are where the females most prefer to lay their eggs. Young grubs and eggs will dry out when the soil is not moist enough. However, older grubs will go deeper into the soil if conditions become dry. They pass winters some 8 to 10 inches below the surface and become inactive when the soil temperature goes below 50 degrees F. The grubs pupate in the Spring and emerge as adults after a month or so. The life of a Japanese beetle is usually between 30 and 45 days.

Control Measures:

  • The adult beetles can be physically removed from the plants and collected in buckets of soapy water by shaking the plant to knock them free.
  • Plants can be protected with nets during the peak Omaha Japanese beetle season.
  • Commercially available traps can reduce large populations. They must be carefully placed. Traps placed close to desirable plants can attract more beetles, which are strongly drawn to attractant odors.
  • Withholding irrigation during the peak beetle flight season may reduce grub populations.
  • Organophosphates and carbamates have been used to chemically control grubs. However, these chemicals often damage other harmless or beneficial insect populations.
  • Two species of tiphid wasps have proven successful as biological agents against Japanese beetles. Other kinds of tachinid flies parasitized the adult beetles, planning eggs in them.

Miller Pest & Termite offers the most comprehensive and all-inclusive pest control program available in Nebraska. Please contact us to learn more.