Maladera castanea Arrow Coleoptera Scarabaeidae

Natural History

Distribution. Asiatic garden beetle was first observed in North America in New Jersey during 1921, but it has since spread as far north as Massachusetts and as far south as South Carolina. Its likely origin is Japan or China.

Host Plants. This insect is reported to feed on more than 100 plants, and though much of the diet breadth is due to adult feeding, larvae also have a wide host range. Larvae normally are most abundant on turfgrass or pastureland, but sometimes they occur in high densities in vegetable and flower gardens, where they attack beet, carrot, corn, lettuce, onion, Swiss chard, strawberry, begonia, columbine, and occasionally others (Hallock, 1934). Among the adult food plants are such crop and ornamental plants as bean, beet, broccoli, cabbage, carrot, corn, eggplant, kohlrabi, parsley, parsnip, pea, pepper, potato, radish, rhubarb, spinach, sweet potato, Swiss chard, turnip, peach, cherry blackberry, sumac, ailanthus, butterfly bush, chrysanthemum, dahlia, larkspur, gaillardia, gerbera, sunflower, strawflower, phlox, viburnum, zinnia, and boxelder. The most favored vegetable crops are beet, carrot, parsnip, pepper, and turnip. Among weeds readily consumed are ragweed, Ambrosia trifida; burdock, Arctium spp.; beggartick, Bidens frondosa; plantain, Plantago spp.; smartweed, Polygonum pensylvanicum; and cocklebur, Xanthium spp. The abundance of larvae is often greater near favored adult food plants, though orange hawkweed, Hiera-cium aurantiacum, which is not a food plant, is a preferred site for oviposition. Larvae also feed on decaying organic matter.

Natural Enemies. A parasitoid, Tiphia asericae Allen and Jaynes (Hymenoptera: Scoliidae), is known from Asiatic garden beetle, though its importance is uncertain. Several microbial pathogens affect Asiatic garden beetle, and likely contribute to periodic population declines. In a survey conducted in Connecticut (Hanula and Andreadis, 1988), infection rates by greg-arines varied from 0-63%, by the protozoan Adelina from 0-67%, and by the bacteria Bacillus popilliae and B. lentimorbus from 0-12.5%. Also observed in Asiatic garden beetle was the rickettsial disease Rickettsiella popilliae, which imparts a blue-green color to grubs.

Life Cycle and Description. There is a single generation per year in New York. Both second and third instars survive the winter, though the majority of larvae are third instars. Pupation occurs in June-July and adults are present from early July through September. Eggs are most abundant from mid-July to August, first instars in August-September, and the latter two instars until the following spring.

  1. The eggs of Asiatic garden beetle are white, oval to nearly spherical in shape, and measure about 1 mm in diameter. They are deposited in the soil in clusters of up to 20 eggs, with the eggs held loosely together by a gelatinous secretion. Egg deposition occurs at soil depths of 1.5-10.0 cm, but mostly between 2.5-5.0 cm. The egg deposition often occurs in the vicinity of favored adult food plants, though sometimes in the vicinity of plants that provide only shelter to adults during the daylight. Mean fecundity is about 60 eggs per female, but the production of up to 180 eggs has been reported. Duration of the egg stage is about 10 days.
  2. The larva is whitish, except for the head, which is brown. The body of the larva is the typical C-shaped form which is so common among scarab beetle larvae. The underside of the terminal abdominal segment bears a curved row of spines that has diagnostic value. There are three larval instars, with the body increasing from about 1.4mm in length at hatching to about 19 mm at maturity. During the spring and summer feeding periods larvae feed within the top 13 cm of soil, though most are located at a depth of 5-8 cm. During the overwintering period the grubs descend to a depth of 15-30 cm. At maturity, the larva creates a small cell in the soil and pupates.
  3. The pupa resembles the adult in general form, except that the wings are shrunken and twisted ventrally. Also, the pupa is tan or light brown and 8-9 mm long. Pupation generally occurs in the soil at a depth of 4-10 cm. Mean duration of the pupal stage is about 10 days (range of 8-15 days).
  4. The Asiatic garden beetle is chestnut brown in color and measures about 8-12 mm long and 46 mm wide. The elytra, which are well-marked with grooves, do not extend the entire length of the abdomen, leaving the terminal abdominal segments exposed. The ventral surface of the adult bears rows of short yellow hairs on each body segment. Adults are nocturnal, hiding during the day on the soil beneath any available cover, or beneath loose soil. They are active only on warm nights, or the warm part of nights. Adults are often found in great number at lights. Duration of the adult stage is about 30 days.

The biology of Asiatic garden beetle was given by Hallock (1932, 1935, 1936). Asiatic garden beetle was included in the larval keys of Ritcher (1966), and the adult keys by Downie and Arnett (1996).

Damage

Asiatic garden beetle is principally a turfgrass pest, though both larvae and adults can injure home gardens. Relative to similar immigrant scarabs, Asiatic garden beetle is generally more damaging to vegetables than oriental beetle, Anomala orientalis Water-house, but is less damaging than Japanese beetle, Popillia japonica Newman. The major form of damage

Natural Predators Japanese Beetles
Adult Asiatic garden beetle.
Scarabaeidae Larval Key
Terminal abdominal segment (ventral view) of Asiatic garden beetle larva.

is root feeding by larvae, but adults feed on foliage and flowers. Damage usually occurs only when large numbers of larvae are present, or in the case of crop seedlings, when plants are quite young. Thus, 2-3 grubs per grass plant affect growth, and 4-5 grubs cause enough root injury to cause plant death. There was also an interesting report of beetles that crawled into the ears of campers in Pennsylvania (Maddock and Fehn, 1958). This form of injury, though affecting hundreds of campers in this report, is not generally a frequent or widespread phenomenon.

Management

Asiatic garden beetle populations are usually cen-sused by sampling turfgrass for grubs. The adults are highly attracted to lights, however, so light traps can be a useful tool for monitoring. Residual insecticide is often applied in either liquid or granular form to the soil for grub suppression, though adults are susceptible to insecticide applied to foliage. Bacillus popil-liae provides partial suppression of larvae.

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  • magnus
    How do i get rid of maladera castanea beetle?
    6 years ago
  • brhane
    How to kill maladera castanea?
    1 month ago

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