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Asiatic Garden Beetle

 
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Asiatic Garden Beetle – Maladera castanea (Arrow)

Injury Symptoms / Impact on Crop

  • Crop injury symptoms are primarily the result of larval root feeding. Symptoms closely resemble root feeding by other grub pests including annual and biennial white grubs and Japanese beetles in the spring.
  • Grub feeding removes root hairs and may damage the mesocotyl between the seed and the main root system. This reduces early vigor until the affected plants can regrow an adequate root system.
  • Asiatic garden beetle adult feeding is rarely a problem in row crops, but may be noticeable on nearby vegetable or ornamental foliage as feeding on the leaves (especially at night and particularly around the leaf edges).

Photos: Corn root feeding

Photo: Asiatic garden beetle field damage
Asiatic garden beetle (AGB) feeding damage may be scattered across a
field, but most severe damage is often concentrated in areas of intensive
egg laying or better survival of larvae. Damage may be compounded by
other factors affecting plant vigor.

Identification

Larvae in the soil

  • Asiatic garden beetle larvae are up to ½ inch long and can be identified most easily by the enlarged maxillary palps just behind the mouth parts. These are light-colored fleshy appendages that appear to be in constant motion.

    Photo: Asistic Garden Beetle larvae

  • Asiatic garden beetle larvae also have a characteristic anal slit and semicircular raster pattern under the tail.

Adults in soil or on foliage

  • Adults are scarab-shaped, tan- or cinnamon-brown-colored beetles with a slight iridescent sheen. They are slightly smaller than Japanese beetles (about 5/16 to 3/8 inch in length).

    Photo: Asiatic Garden Beetle adult on foliage

Related or Often Misidentified Grubs

  • Manure scarabs - generally smaller size, found associated with pastures or manure.

    Photo: manure sarabs

  • Annual, biennial grubs and Japanese beetle - generally above 1/2 inch in length with a different raster pattern and no maxillary palps.

    Diagram: Comparison of raster patterns

Pest Facts

  • General feeding habits – Sporadic root pest of root crops, foliar feeding by adults.
  • Host range – Wide host range, over 100 hosts are known, primarily perennial ornamentals but also feed on vegetables and row crops.
  • Distribution – Introduced to the Northeast U.S. from Japan in the 1920s. From there, it has spread westward and southward as far as Indiana and South Carolina
  • Natural enemies – Although there are naturally occurring diseases and nematodes, there are no major native enemies of this imported pest.

Life Cycle of Asiatic Garden Beetle


Chart: Asiatic Garden Beetle Life Cycle
 

Management Considerations for Asiatic Garden Beetle

  • Trapping
     
    • Limited success of identifying elevated grub numbers prior to planting has been made with wireworm bait stations.
    • Adult populations have also been monitored with immersion-type western bean cutworm traps.
  • Scouting
     
    • Asiatic garden beetles are attracted to lights and feed on foliage. Monitor these sources to determine relative populations in an area.
  • Winter survival
     
    • Soil disturbance may promote larval mortality and predation to a low degree; thus, no-till may be conducive to higher survival.
    • Dry soils that promote desiccation are least conducive to winter survival.
  • Native resistance
     
    • No crop or plant resistance to the Asiatic garden beetle is known.
  • Pesticide use
     
    • The best approach to management is to monitor the populations and use a preventive soil insecticide1 or insecticide seed treatment1 at planting.
    • If early stand loss is excessive and replant is needed, use a soil insecticide if grubs are still active.

References

  • Hallock, H.C. and I. M. Hawley, Life history and control of the Asiatic garden beetle, Circular 246 revised, USDA. 1936.
  • Koppenhöfer, A. 2013. Managing turfgrass insects of the Northeast: Part 2: Root-infesting insect pests. Rutgers University.
  • Mackellar, B. 2011. Asiatic garden beetle, a new pest of corn, potato, and alfalfa in SW Michigan, CCD #034. Michigan State Univ.
  • MacKellar, B. 2012. How to determine if your corn field is at risk of Asiatic garden beetles. Michigan State University.
  • Shetlar, D. and H. D. Niemczyk, 1999. Asiatic garden beetle. Ohio State University.
  • Tiwari, S, C.A. Lamb and R. R. Youngman, 2009. Asiatic garden beetle in field corn. Virginia Tech Pub 444-108.


1 Product responses are variable and subject to a variety of environmental, disease and pest pressures. Individual results may vary.

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