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Why Do Japanese Beetle Adults Feed on Certain Plant Types?

July 7, 2004

Japanese beetle, Popillia japonica, adults are a major insect pest of cultivated plants in landscapes because they feed on a wide variety of plant types (> 300 plant species), including annuals, perennials, trees, shrubs, and vines. However, certain plant types are more susceptible to attack than others (refer to Table 1, p. 4) although there may be considerable variation among susceptible plant types, especially birch, crabapple, elm, and linden. In contrast, a number of plants are less susceptible to attack by Japanese beetle adults. These plants are listed in Table 2, p. 4.

A number of factors influence the level of plant susceptibility to Japanese beetle adult feeding, including amount of sunlight plants receive and flower color. For example, Japanese beetles prefer to feed on roses located in full sun, whereas roses located in wooded areas are seldom attacked. White and yellow rose flowers tend to attract more Japanese beetle adults, thus suffering more extensive flower damage than darker colors such as apricot, orange, pink, mauve, and red.

Japanese beetles also use plant odors and damage-induced plant volatiles to locate plants. They are attracted to a complex of volatile compounds produced by plants. Studies have demonstrated that leaves of plants that have been fed upon by adult Japanese beetles (and even other herbivores) produce induced odors that attract additional adult beetles. Leaves damaged by Japanese beetle adults produce a complex mixture of aliphatic compounds, phenylpropanoid-derived compounds, and terpenoids. Research has also shown that natural sugar content and presence of odoriferous substances are important factors in determining the susceptibility of plants to attack by Japanese beetle adults. For example, plants with higher amounts of the reducing sugar dextrose suffer greater damage from adult beetles than plants with lower amounts of dextrose.

Chemical odors have also been implicated in the attractiveness of certain plants to Japanese beetles. The ornamental tree, Ginkgo biloba, which is not typically attacked by adult Japanese beetles, lacks certain chemical odors that are attractive to them. However, many susceptible plants such as rose and apple contain the substance geraniol, which is highly attractive to Japanese beetle adults. It is important to note that when Japanese beetle adult populations are excessive and food is a limiting factor, plants that are supposedly less susceptible to adult Japanese beetle feeding may be fed upon.

Table 1. Ornamental plants highly susceptible to feeding by Japanese beetle, Popillia japonica adults.

Japanese maple (Acer palmatum)

Norway maple (Acer platanoides)

Gray birch (Betula populifolia)

Horsechestnut (Aesculus spp.)

Black walnut (Juglans nigra)

Sassafras (Sassafras spp.)

American elm (Ulmus americana)

Althea (Althaea spp.)

London planetree (Platanus x acerifolia)

Rose (Rosa spp.)

Black cherry (Prunus serotina)

Crabapple (Malus spp.)

American mountain ash (Sorbus americana)

Lombardy poplar (Populus nigra ‘Italica’)

Pussy willow (Salix discolor)

American linden (Tilia americana)

Table 2. Ornamental plants less susceptible to feeding by Japanese beetle, Popillia japonica adults.

Red maple (Acer rubrum)

Silver maple (Acer saccharinum)

American holly (Ilex opaca)

Boxwood (Buxus spp.)

Snowberry (Symphoricarpos spp.)

Winged euonymus (Euonymus alata)

Flowering dogwood (Cornus florida)

White cedar (Thuja occidentalis)

Yellow poplar (Liriodendron tulipifera)

Saucer magnolia (Magnolia x Soulangiana)

White ash (Fraxinus americana)

Green ash (Fraxinus pennsylvanica)

Lilac (Syringa spp.)

Norway spruce (Picea abies)

Scotch pine (Pinus sylvestris)

Douglas fir (Pseudotsuga menziesii)

Canadian hemlock (Tsuga canadensis)

Mock orange (Philadelphus spp.)

Hydrangea (Hydrangea spp.)

Yew (Taxus spp.)

Forsythia (Forsythia spp.)

Author: Raymond A. Cloyd


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