Oriental Beetle Anomala orientalis Waterhouse Coleoptera Scarabaeidae

Natural History

Distribution. Oriental beetle is an immigrant species. It likely originated in the Philippines or Japan, but was found in Hawaii in 1908 and Connecticut in 1920. It has since spread to other northeastern states and southward, with its current distribution extending from Massachusetts and New York in the north to North Carolina in the south, and also in Ohio near Lake Erie. Since its initial introduction, its rate of spread has been surprisingly slow.

Host Plants. Oriental beetle causes relatively little injury to vegetables, though it may feed on bean, beet, onion, and rhubarb. Also, sugarcane is severely damaged in Hawaii, as well as strawberry and nursery stock in the northeastern states. Oriental beetle is principally a pest of turfgrass, where the larval stage attacks roots. Other plants occasionally injured, principally by the adults, include such flowers as dahlia, hollyhock, phlox, and rose. Most damage to economically important plants results from feeding by the larval stage.

Natural Enemies. Several natural enemies were imported into Hawaii and released, including two species which were successfully established—Campsome-ris marginella modesta Smith (Hymenoptera: Scoliidae) and Tiphia segregata Crawford (Hymenoptera: Tiphii-dae). The former species is considered to be quite important as a mortality agent of larvae. Although at least five species of scoliids were introduced to the northeastern states, no parasitoids were successfully established. However, a survey of microbial pathogens in Connecticut (Hanula and Andreadis, 1988) demonstrated that gregarines infected up to 100% of the population and Bacillus popillae was found in up to 25% of the grubs sampled. Although the effect of these pathogens is not known, they likely help to suppress population densities of oriental beetle. Birds are sometimes observed to flock to grub-infested turfgrass, where they feed extensively on larvae. Weather also seems to limit the abundance of oriental beetle, and populations diminish during abnormally dry summers.

Life Cycle and Description. Although a complete life cycle may be completed in only three months in Hawaii, there normally is but a single generation annually in the temperate climate of the northeastern states. In New England, some individuals even require a second year to complete their development. Overwintering normally occurs in the last larval instar. In Connecticut, larvae feed during April-June, and pupate in June. Pupae transform to adults in late June-August, and emerge from the soil within a few days. Following mating and oviposition, eggs begin to hatch in July and August. Larvae usually attain the third instar by late September.

  1. The eggs are oval in shape. They typically measure about 1.2 mm wide and 1.5 mm long when first deposited, but swell slightly as they absorb water, and increase to 1.6 mm wide and 2.0 mm long. The period of incubation is about 17 days at 24° C, averaging 25-28 days under field conditions.
  2. Upon hatching the larva digs nearly to the surface to feed on roots and dead organic matter. Larvae display three instars. The first and second instars each require about 30-40 days to complete their development. The third instar overwinters, moving from a feeding position near the soil surface to greater depth in the soil, often 25-40 cm. Larvae are about 4 mm long following hatching, and attain a length of about 4, 15, and 20-25 mm by the end of instars 1-3, respectively. Head capsule width is about 1.2, 1.9, and 2.9 mm, respectively, for the corresponding instars. The larva is similar in form to other scarab grubs—thick bodied and C-shaped. Its body is whitish, though the head is brown. The body bears numerous short hairs, with the arrangement of hairs on the ventral surface of the terminal abdominal segment important for diagnostic purposes.
  3. Pupation occurs in early June when larvae dig to a depth of 3-20 cm and create a small cell. The mature larva remains in the cell for 5-8 days before molting to a pupa. The duration of the pupal stage is about 15 days. The pupa is about 10 mm long and 5 mm wide, and light brown in color. The pupa generally resembles the adult though the wings are short and twisted to the ventral surface.
  4. The adults are elongate-oval, and more tapered at the anterior end. The elytra bear pronounced ridges. The male beetles measure about 9 mm long and 4 mm wide; the females measure about 10.3 mm
Terminal abdominal segment (ventral view) of oriental beetle larva.

and 4.5 mm, respectively. The beetles are highly variable in coloration, ranging from yellowish brown to black. However, the head is invariably black, and the pronotum usually bears two moderately sized irregular black areas that coalesce into a single large spot in darker forms. The elytra often bear irregular black areas that form a V-shaped pattern, but as noted previously, coloration is not consistent in this species. Adults are active during morning and afternoon as well as at night. They may be attracted to flowers, where they feed slightly, or to lights. Females produce a sex pheromone that attracts males (Zhang et al., 1994). Both sexes mate repeatedly, and females commence oviposition within 1-5 days of mating. Oviposi-tion normally continues for about seven days (range 4-20 days). Females burrow into the soil, usually to a depth of 10-20 cm, to deposit eggs.

Detailed description and biology were provided by Friend (1929). The larva of oriental beetle was included in the key by Ritcher (1966), and the adults in the keys of Downie and Arnett (1996).

Damage

Damage is caused principally by the larval stage, which feeds on the roots of plants. Adults are generally considered to be of no consequence, though occasionally they feed on foliage of vegetable crops. Normally, only turfgrass experiences severe injury, but other plants are sometimes damaged. In the northeastern states, where oriental beetle co-occurs with Japanese beetle, Popillia japonica Newman, and Asiatic garden beetle, Maladera castanea (Arrow), the oriental beetle is sometimes the most important cause of turfgrass injury (Adams, 1949; Facundo et al., 1994).

Management

Population density is usually assessed by examining areas of dead or dying sod for the presence of larvae. However, populations also may be monitored with sex pheromone-baited traps (Facundo et al., 1994; Alm et al., 1999). Applications of insecticide or Bacillus popillae to turfgrass are the principal methods of oriental beetle suppression. The susceptibility of

Bicillus Popillae
Adult oriental beetle, various color forms.

oriental beetle grubs to B. popillae seems to vary over time, perhaps accounting for some of the variation in abundance (Dunbar and Beard, 1975). Compared to some other turf-damaging species, oriental beetle is relatively susceptible to most insecticides (Villani et al., 1988), though there may be site-related differences in field efficacy (Baker, 1986). Oriental beetle seems to be relatively non-susceptible to entomo-pathogenic nematodes (Nematoda: Steinernematidae, Heterorhabditidae) (Alm et al., 1992).

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Responses

  • Victor
    Where is the oriental beetle when it spreads?
    6 years ago
  • tanta roper
    Are there Popillia japonica in hawaii?
    6 years ago
  • primula
    Are oriental beetles bad for hawaii?
    5 years ago

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