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Species Page

Japanese beetle

Popillia japonica
This information is part of a full datasheet available in the Crop Protection Compendium (CPC);www.cabi.org/cpc. For information on how to access the CPC, click here.
©CAB International. Published under a CC-BY-NC-SA 4.0 licence.

Distribution

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Host plants / species affected

Main hosts

show all species affected
Acer (maples)
Asparagus officinalis (asparagus)
Glycine max (soyabean)
Malus (ornamental species apple)
Prunus (stone fruit)
Rheum hybridum (rhubarb)
Rosa (roses)
Rubus (blackberry, raspberry)
Tilia (limes)
Ulmus (elms)
Vitis (grape)
Zea mays (maize)

List of symptoms / signs

Fruit - abnormal shape
Fruit - external feeding
Inflorescence - external feeding
Leaves - external feeding
Roots - external feeding
Roots - reduced root system
Whole plant - dwarfing
Whole plant - external feeding
Whole plant - plant dead; dieback

Symptoms

Skeletonized foliage is the most common symptom of feeding by the adult. The beetles generally feed from the upper surface of leaves, chewing out the tissue between the veins and leaving a lacelike skeleton. Severely damaged leaves soon turn brown and drop. The adults are gregarious, usually beginning to feed on foliage at the top of a plant and working downward. On some plants with thin leaves and fine venation, and on petals of flowers, the beetles consume irregularly-shaped sections in the same manner as many Lepidoptera. Plants with thick, tough leaves are usually not attacked, but when such leaves are eaten (Concord grapes), the feeding is often restricted to the palisade mesophyll and does not penetrate to the lower leaf surface.

Maize is one field crop seriously damaged in North America. The beetles feed on the maturing silk, preventing pollination; this results in malformed kernels and reduced yield. This appears to be more of a back-yard maize growing situation because the light-loving beetles rarely venture more than 1-2 rows into a maize field. However, beetles can feed over an entire soyabean field and cause their damage. They also defoliate asparagus, nearly all varieties of grapes, and many fruit-bearing trees, especially apple, cherry, plum, and peach. Beetles can aggregate and feed in large numbers on the fruit of early-ripening varieties of apple, peach, nectarine, plum, raspberries, and quince. This feeding renders fruit unmarketable, unless they have been protected by pesticides.

The larvae are most abundant in well-kept lawns and golf courses, and less often in pastures. As the grub feeds just below the surface, it cuts off and consumes the grass roots. Early symptoms include thinning, yellowing, and wilting, culminating in large patches of dead, brown grass that appears in late summer or early autumn because of water stress, and less often in the following spring when more moisture is normally available. When grubs are numerous (400/m2+) the root system is completely severed and the sod can be lifted or rolled back like a carpet. Secondary damage from skunks, raccoons, crows, or other predators often causes more disruption to the sward than the grubs themselves. Feeding by grubs on roots of maize, beans, tomatoes, strawberries, nursery seedlings, or other crops reduces their vitality and yield and sometimes kills the plants. Damage is often most severe when these crops are planted into areas which were previously turf.

Prevention and control

Introduction

The destructive potential and economic importance of this pest have led to intensive studies of various means for control. Note that the adults and grubs cause very different types of damage, above ground and below ground. Because the adults can fly considerable distances, controlling one life stage will not necessarily preclude problems with the other.

Control

Host-plant resistance

Fleming (1972a) provided a ranking of the extent of feeding by adult P. japonica on 435 plant species in 95 families. Within some generally susceptible genera such as Betula, Malus and Tilia, less susceptible cultivars have been found (Ranney and Walgenbach, 1992; Spicer et al. 1995; Potter et al., 1998). Use of resistant, or less susceptible species and cultivars when planning a landscape, or replacing damaged plant material, is a key to managing adults. Highly susceptible trees such as Sassafras, Prunus cerasifera, Ancer ploatanoides, and Tillia spp., or certain wild plants, such as species of Malva, Parthenocissus, Polygonum, and Vitis, will attract numerous beetles.

Although tolerance varies, all species of cool-season turfgrasses are susceptible to the grubs (Potter et al., 1992). Infection of tall fescue, Festuca arundinacae or perennial ryegrass, Lolium perenne, with fungal endophytes (Neotyphodium spp.) does not provide resistance to this pest.

Physical removal and exclusion

Hand removal may provide some control for small plantings. Beetles on plants are sluggish in the morning, before 9 am, or when the temperature is <21oC, and can be killed by picking them, or shaking them, into a bucket of soapy water (Ladd and Klein, 1982). This is most effective when done before damage to the plants. High-value plants such as roses can be protected with fine netting or Reemay fabric around each blossom during the period of beetle activity.

Trapping

Although mass trapping has held isolated populations in check, and reduced the regulatory situation at some airports, it has not been effective in reducing established P. japonica infestations. However, Japanese beetle traps are an important tool in the identification and delimitation of new P. japonica infestations. California (Potter and Held, 2002) and Oregon monitor 10,000 and 5,000 traps per year, respectively, and have both eradicated isolated infestations in their states. Other western states utilize traps to a lesser extent. Small-scale trapping may aggravate defoliation damage in landscapes because the traps may attract more beetles than actually enter the traps (Gordon and Potter, 1985). Although beetles can fly up to 5 miles, they rarely do, and are not attracted to traps more than 50-100 m away (Lacey et al., 1994).

Cultural control

Female beetles seek out sites that are most optimal for egg laying and survival (Allsopp et al., 1992). Withholding irrigation during peak beetle flight can help to reduce subsequent grub populations in time of drought, and in naturally dry areas (Potter et al., 1996). In contrast, rainfall or irrigation in summer and early autumn, during early instar feeding, promotes tolerance and recovery of grub-damaged turfgrass. Vigorous, well-watered turf can withstand two to three times the normal threshold of grubs (ca. 100/m2) that would destroy a weak, wilted, or starved sward. Raising cutting height, and maintaining a balanced fertility regime to promote growth of roots also enhances tolerance of root-feeding by grubs (Crutchfield et al., 1995).

Biological control

During 1920-1933, the USDA imported about 49 species of parasites of P. japonica and related scarabs from the orient and Australia and released them into Japanese beetle-infested areas in the USA (Fleming, 1968). Only a few of these became established, the most widely distributed are Tiphia vernalis, a wasp that parasitizes overwintered grubs in the spring, and Istocheta aldrichi, a tachinid fly that parasitizes adults (http://www.oardc.ohio-state.edu/biologicalcontrol). The spring Tiphia seems to be well-established throughout the beetle-inhabiting areas. Istocheta had been restricted to the New England states, but has recently been established in North Carolina, Michigan, Minnesota, and Missouri, USA (Jackson and Klein, 2006). A third established parasitoid, Tiphia popilliavora, the fall tiphia, has not been recovered since 1969, although isolated populations may still be present. These parasitoids provide some suppression, particularly I. aldrichi, in areas with restricted turf, but do not usually provide adequate beetle control.

Spores of Paenibacillus (=Bacillus) popilliae, the primary causal agent of milky disease in P. japonica were widely distributed in colonization programmes around the middle of the last century in eastern USA (Fleming, 1968). Although milky disease is one of the primary natural biological agents reducing Japanese beetle populations, the value of augmenting this natural incidence with commercial spore powder has come under question (Redmond and Potter, 1995; Potter and Held, 2002; Jackson and Klein, 2006). Another bacterium, Bacillus thuringiensis – serovar japonensis, strain Buibui, has shown strong larvacidal activity against P. japonica and other grubs (Ohba et al., 1992; Alm et al., 1997), but lacks a commercial product in the USA.

Entomopathogenic nematodes in the genera Steinernema and Heterorhabditis are the most commonly used pathogens against P. japonica. Nematodes such as Steinernema glaseri and Heterorhabditis bacteriophora are better-adapted to locate and parasitize the grubs in the soil (Gaugler et al., 1997). Wright et al. (1988) showed that nematodes could be used to control P. japonica grubs in container-grown nursery plants. Techniques for using these nematodes can be found at http://www.oardc.ohio-state.edu/nematodes, or in the training video “Entomopathogenic Nematodes: Tools for pest management” (Gaugler and Klein, 1998). Autodissemination of the fungus Metarrhizium anisopliae has been used to suppress Japanese beetle populations in the Azores and the USA (Klein and Lacey, 1999; Vega et al., 2007).

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

Impact

P. japonica is the single most destructive insect pest on golf courses, lawns and pastures, and on herbaceous and woody landscape plants in the eastern USA (Tashiro, 1987; Potter, 1998; Vittum et al., 1999). A decade ago it was estimated that more than $460 million is spent each year to control the grubs and adults, and about $156 million in renovating or replacing damaged turf or ornamental plants (USDA/APHIS, 2000). Damage to tree fruits, small fruits, maize, and soybeans is also significant. In addition, many millions of US dollars, and considerable quantities of pesticides, are also lost trying to limit the beetle’s spread by nursery stock and aeroplanes in North America. The Japanese beetle has never been a major pest in Japan, and has not caused extensive damage up to this point in the Azores. Costs connected with quarantine concerns are likely to increase greatly with the discovery of the beetle on San Miguel Island, USA.