Invasion of the Japanese Beetles

Information provided by Jim Jarman, Central Missouri Extension Region Agronomy Specialist. (jarmanj@missouri.edu)

Just about everyone will benefit from monitoring prize plants in gardens and crops. Japanese Beetles (JB) feed on a wide number of plants. The most damaging feeding injury in vegetable gardens is probably feeding on corn silks. During hot, dry weather pollination can be a problem for corn even if something is not eating off the silks. They will also attack ripening fruit, flowers and leaves. The immature stage of growth is a grub which feeds on the roots of grasses and plants. The larvae prefer lighter, sandy soils so larger numbers may be found near creeks and river bottoms. In central Missouri more JB have been trapped in Jefferson City along the Missouri River than Fulton. 

Get to know what JBs look like and watch for them in ornamental and vegetable gardens. They are in the same family as the scarab or June beetles. Adults may be separated from other scarabs by their metallic green color, copper coloring across the back (wing covers), and six white short hairy tufts on each side of the abdomen. Most of the June beetle species in Missouri are larger. The Japanese beetle usually measures 3/8 to ½ inch in length. County Extension Centers have lists of the JB’s favorite host plants, but a partial list is provided below.

When JB are infesting, check pesticides on hand for the infested host plant and JB to be listed on the label. Extension specialists use traps to monitor the numbers and timing of when they occur. Traps are known for attracting more insects than they catch. It would take a high number of traps in a small area to control a localized infestation. Plus traps have to be emptied frequently and most of the beetles will still be alive. See the MU Extension web site: http://extension.missouri.edu/p/IPM1020-19 for photographs and more information. 

In vegetable gardens plants Japanese beetles like:

Japanese Beetles DO NOT like

Green beans and other beans Strawberries Tomatoes                                              Peach tree leaves Blueberries Peppers Grapes                                                   Hops Cherries                                                 Plums Pears                      Peaches Raspberries                                           Blackberries Corn Peas and others from  these general families

Chives Garlic Tansy Catnip

Landscape plants nearly always severely attacked by adult Japanese beetle.

American chestnut	Hollyhock
American elm	Horse chestnut
American linden	Japanese maple
American mountain-ash	Lombardy poplar
Black walnut	London planetree
Cherry, black cherry, plum, peach, etc	Norway maple
Roses	Crape myrtle
English elm(shrub Althea)	Rose-of-Sharon
Flowering crabapple, apple	Sassafras
Gray birch	Table grapes

Landscape plants relatively free of feeding by adult Japanese beetle.

American elderberry	Magnolia
American sweetgum	Persimmon
Black oak	Red maple
Boxelder	Red mulberry
Boxwood	Red oak
Butternut	Rhododendron
Common lilac	Scarlet oak
Common pear	Shagbark hickory
Evergreens (fir, spruce, pine)	Silver maple
Euonymus	Tuliptree
Flowering dogwood	White ash
Green ash	White oak
Hemlock	White poplar
Holly