Maladera castanea

Potential Invader

Common name(s)

Asian garden beetle, Asiatic garden beetle

Taxonomy

Family: Scarabaeidae Subfamily: Melolonthinae Genus: Maladera Species: Maladera castanea (Arrow, 1913)

Adult diagnosis

Total body length 7.0–11.0 mm (0.28–0.43). Body shape oblong-oval, widest posteriorly; convex when viewed laterally. Color rusty-brown to orange-brown with iridescent sheen. Clypeus with anterior margin strongly reflexed. Antennae 10-segmented; club 3-segmented. Pronotum with indistinct, shallow punctation. Elytra lacking obvious setae. Front tibia of female more robust than in male.

Larval diagnosis

(Ritcher, 1966): Grub C-shaped, not hump-backed, cylindrical, whitish. Cardo, maxillary articulating membrane, and many other body parts with numerous black dots. Galea and lacinia fused proximally, but separated distally or tightly fitted together. Maxilla with dramatically swollen, bulbous stipes. Maxillary stridulatory area with row of 17–20 peg-like teeth. Last antennal segment always with a single, large, oblong, dorsal, sensory spot. Haptomerum with 3 or 4 heli. Dorsal anal lobe much smaller than the ventral anal lobes. Anal lobes densely setose. Raster with a curved, transverse row of prominent setae anterior to the ventral anal lobes. Anal opening Y-shaped with base of the Y much more elongate than the arms.

Native range

Northeastern Asia. This species is known from temperate northeastern Asia, occurring in Korea, China, and the Russian Far East (Ahrens, 2007). In the mainland U.S., this species is known from Maine west to Kansas and south to northernmost Florida (Skelley, 2012).

Plant host(s)

The adults of this scarab have been recorded feeding on the foliage, stems, and flowers of over 100 plant species (Skelley, 2012). Economically important host plants damaged by adults include Aster spp., basil (Ocimum basilicum), beans (Phaseolus spp.), beet (Beta vulgaris), Begonia spp., blackberry (Rubus spp.), blueberry (Vaccinium spp.), broccoli (Brassica oleracea), cabbage (Brassica oleracea), carrot (Daucus carota), cherry (Prunus spp.), Chrysanthemum spp., currant (Ribes spp.), Dahlia spp., eggplant (Solanum melongena), foxglove (Digitalis spp.), Geranium spp., hemp (Cannabis spp.), lettuce (Lactuca sativa), morning-glory (Ipomoea spp.), pea (Pisum sativum), peach (Prunus persica), plum (Prunus spp.), bell pepper (Capsicum annuum), rose (Rosa spp.), spinach (Spinacia oleracea), strawberry (Fragaria × ananassa), sunflower (Helianthus annuus), turnip (Brassica rapa), Viburnum spp., and willow (Salix spp.) (Eckman, 2015). Larvae, too, are generalist herbivores and have been recorded feeding on the roots of such economically important plants as blueberries (Vaccinium spp.), corn (Zea mays), soy beans (Glycine max), sweet potato (Ipomoea batatas), and turf grasses (Skelley, 2012).

Life history

(Eckman, 2015): In New York, females of this species deposit eggs in soil between July and October, showing a preference for shady, moist, overgrown, and weedy areas. After emerging, the larvae burrow to a depth of 15–30 cm (5.9-11.8 in) and begin feeding of plant roots. Winter is passed in the second or third larval instar and feeding usually resumes by mid-April. Roughly ten months are spent in the larval stage, with pupation lasting 14 days. Adult emergence begins in July, but likely begins earlier in warmer climates. Adults can live for more than 100 days, although the average lifespan is closer to 30 days. Adults are nocturnal and fly only when temperatures exceed 16°C (70°F). During the day, adults are inactive and remain near or on host plants.

Pest potential

Major. This species is a known biosecurity threat with a history of biological invasion (Ahrens, 2007). Invasive populations have become established in Canada (Cutler and Rogers, 1990), Turkey, the Republic of Georgia, and the US (Ahrens, 2007). In the US, the range of this species has expanded slowly but steadily since its 1921 introduction (Skelly, 2012). Adults cause severe leaf damage to a wide range of plant species important for agriculture, horticulture, and forestry (Eckman, 2015). Larvae feed on plant roots and can cause significant damage, particularly to turf grass (Held and Ray, 2009). The pest potential of larvae is reduced somewhat by their tendency to burrow deep into soils, and their preference for weedy, unkempt habitats (Skelley, 2012).

Status in Hawaii

New record, not established. We recorded a single specimen of Maladera castanea from Oahu (deposited at the Bernice Pauahi Bishop Museum). The specimen label indicates it was discovered at Hickham Air Force Base in a spider's web in 1977.

Status in Guam

Not established or recorded. This species has not been recorded from Guam.

Potential distribution and dispersal pathway

This species is strongly attracted to lights at night (Held and Ray, 2009), and it is likely attracted to well-lit ports and airports. This would allow for hitchhiking on marine or air cargo. Indeed, the Oahu record may represent an individual that hitchhiked aboard military aircraft. Adults hide on or near food plants by day (Eckman, 2015) and could be moved during transportation of nursery plants. Further, it is possible that larvae or eggs could be transported in shipments of commercial turf or potted plants.

Similar species

This species is very similar to the closely related Maladera japonica. These species can be separated by comparison of the male genitalia, examination of pronotal punctation (punctures shallow and indistinct in M. castanea versus moderately deep and distinct in M. japonica), and more superficially by color (color rusty-brown to orange-brown with iridescent sheen in M. castanea versus dark brown without iridescent sheen in M. japonica).

Other names (synonyms)

Aserica castanea (Hallock), Autoserica castanea (Hallock), Maladera verticalis (Fairmaire), Serica korgei Petrovitz, Serica verticalis Fairmaire

Report your observation

In Hawaii, this species represents a new invasive species. Prevent the spread of this species by reporting your observation at our iNaturalist project.

Maladera castanea male; photo by E.L. Engasser

Maladera castanea male; photo by E.L. Engasser

Maladera castanea male; photo by E.L. Engasser

Maladera castanea male; photo by E.L. Engasser

Maladera castanea male foretibia; photo by E.L. Engasser

Maladera castanea male foretibia; photo by E.L. Engasser

Maladera castanea female foretibia; photo by E.L. Engasser

Maladera castanea female foretibia; photo by E.L. Engasser

Maladera castanea male genitalia, dorsal view; photo by E.L. Engasser

Maladera castanea male genitalia, dorsal view; photo by E.L. Engasser

Maladera castanea male genitalia, lateral view of right side; photo by E.L. Engasser

Maladera castanea male genitalia, lateral view of right side; photo by E.L. Engasser

Maladera castanea male genitalia, lateral view of left side; photo by E.L. Engasser

Maladera castanea male genitalia, lateral view of left side; photo by E.L. Engasser

distribution map for Maladera castanea

distribution map for Maladera castanea