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How to Protect Your Trees and Shrubs From Japanese Beetle Damage

By Julie Bawden-Davis

The Japanese beetle, a most destructive garden pest, devours just about everything in its path, including well-tended trees and shrubs. The damage it causes is disheartening, but you can arm yourself with knowledge and keep this pest under control in your yard.

A Foreign Menace

As its name suggests, the Japanese beetle is a native of Japan, where it has natural enemies that keep it in check. The U.S. Department of Agriculture reports that the pest was first sighted in the United States at a southern New Jersey nursery in 1916.1 Because natural enemies of the beetle don't exist in the U.S., the pest has wreaked havoc on plants since its arrival. It took only four years for the pest to cause severe damage in 22 states after making its way to America. Monitoring and rigid regulations have helped prevent or slow the pest's establishment in the remaining states.1

Beautiful but Destructive

At a little less than 1/2 inch long, the Japanese beetle is hardly imposing. In fact, it might be considered somewhat attractive. The oval-shaped insect is metallic green with bronze-colored wing covers and dark legs. A telltale characteristic that distinguishes the Japanese beetle from other beetle types is the series of small, white tufts of hair located under the wing covers along each side of its body and on its hind end.

In the spring or early summer, adult female beetles lay eggs in soil. Those eggs hatch and become unattractive larvae known as grubs. The white, c-shaped grubs have dark heads and feed on plant roots, often causing severe damage. The larvae stay in the soil until the following spring, when they pupate and become adults.

Hungry Invader

The Japanese beetle has a voracious appetite that makes it especially destructive. The adult beetle feeds on about 300 species of plants — roses, shrubs, vines, ornamental and fruit trees, and vegetable crops — devouring foliage, flowers, tree and shrub buds, and fruit.2

Because of its distinctive feeding pattern, Japanese beetle damage to trees and shrubs is easy to spot. The pests dine on the soft tissue between leaf veins, leaving leaves skeletonized and lace-like. Flower petals become ragged after beetles feed on them; trees hit hard by beetle feeding may appear as though scorched by fire.2

Japanese beetles are most active on warm, sunny days and like to feed in direct sun in groups. The adult beetles are able to fly, which allows them to move easily and quickly throughout your landscape and join others. They begin eating at the top of plants and work their way down.3

Pest ID & Prevention

These pesky creatures devour a wide variety of plants and trees, including:

  • American Chestnut
  • American Elm
  • American Linden
  • American Mountain Ash
  • Apricot
  • Black Walnut
  • Cherry
  • Crabapple (flowering)
  • Crape Myrtle
  • Dahlia
  • English Elm
  • Evening Primrose
  • Grape
  • Gray Birch
  • Hibiscus
  • Hollyhock
  • Horse Chestnut
  • Japanese Maple
  • Lombardy Poplar
  • London Planetree
  • Mallow
  • Norway Maple
  • Peach
  • Pin Oak
  • Plum
  • Rose
  • Rose-of-Sharon
  • Soybean
  • Sweet Corn

Control Measures

Keeping Japanese beetles under control in your yard requires a multi-pronged approach:

Physical Removal

When the number of beetles is low, removing them by hand and then destroying them is a good option. Remove them in the early morning hours, when they are less active, and place them in a collection container filled with soapy water.4

Plant Exclusion

Avoid planting large numbers of plants known to attract Japanese beetles. If planted, intermix them with plants that the beetles don't find as tempting, such as:

  • American Elder
  • American Sweetgum
  • Begonia
  • Boxwood
  • Columbine
  • Coral Bells
  • Dogwood
  • Euonymus
  • Foxglove
  • Green Bean
  • Holly
  • Hosta
  • Impatiens
  • Juniper
  • Lantana
  • Larkspur
  • Lilac
  • Nasturtium
  • Pansy
  • Pear
  • Persimmon
  • Raspberry
  • Red and Silver Maple
  • Red Mulberry
  • Tuliptree
  • Virginia Creeper
  • White and Green Ash
  • White Poplar
  • White/Red/Scarlet/Black oak

Weeding

Japanese beetles like dining on weeds along with other plants, so keep the garden tidy. It eliminates beetle food and hiding places as well.

Pesticide Application

Japanese beetles are persistent, so an effective, trusted pesticide is an important part of any control plan. Highly effective Sevin® brand garden insecticides from GardenTech are tough on beetles, but gentle on gardens. You can choose the product type that works best for you.

Sevin® Insect Killer Ready To Use, in a convenient spray bottle, kills Japanese beetles and more than 500 types of insect pests by contact. Then, it keeps on working and protecting your plants against pests for up to three months. For hose-end spraying, get the same highly effective, long-lasting protection with Sevin® Insect Killer Ready To Spray; use Sevin® Insect Killer Concentrate for larger areas and backpack or tank sprayers.

A thin, even layer of Sevin®-5 Ready-To-Use 5% Dust treats Japanese beetles on ornamental shrubs and small trees, working best at chest height or lower. Leave taller plants to liquid Sevin® products. For trees over 10 feet tall or plants you can't spray effectively because of their size, call in a horticulture professional to apply the pesticide.

To fight Japanese beetles at the grub stage as well as adults, Sevin® Insect Killer Granules works above and below the surface to kill beetle larvae along with more than 100 other insect pests. Applied according to directions, the granules kill pests by contact and protect your lawn, edible and ornamental gardens, and other areas around your home for up to three months.

Japanese beetles put up a good fight in your garden, but GardenTech® and Sevin® brands are here to help. With preparation, regular tending and highly effective products, you can prevent these pests from damaging your trees and shrubs, and get back to enjoying your landscape.

Total Time to Keep Japanese Beetles under Control: 1-2 hours per week during spring

Effort rating: 2 - Easy Does It

Time breakdown (depending on the number of plants affected):

  • Locate beetle infestation areas: 15 minutes
  • Handpick beetles from highly concentrated infestation areas: 15-45 minutes
  • Apply control product: 30-60 minutes

Always read product labels thoroughly and follow instructions carefully, including guidelines for application frequency and pre-harvest intervals (PHI) on edible crops.

GardenTech is a registered trademark of Gulfstream Home and Garden, Inc.

Sevin is a registered trademark of Tessenderlo Kerley, Inc.


Sources:

1. USDA Animal and Plant Health, “Managing the Japanese Beetle: A Homeowner's Handbook," United States Department of Agriculture, August 2015.

2. M.F. Potter, et al., "Japanese Beetles in the Urban Landscape," University of Kentucky College of Agriculture, Food and Environment, January 2006.

3. Vera Krischik and Doree Maser, "Japanese Beetle Management in Minnesota," University of Minnesota Extension, 2011.

4. W. Cranshaw, "Japanese Beetle," Colorado State University Extension, May 2013.

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