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Japanese Beetle

Symptoms and Impact on Crop

Japanese beetles feeding on corn
 
Japanese beetle on corn leaf
  • Clipped corn silks from the Japanese beetle may reduce pollination and yield
  • Skeletonized or lacy leaf patterns between veins are symptoms of either corn or soybean feeding
  • Leaf feeding is typically insignificant in corn
  • Leaf feeding may be more significant in soybeans, causing defoliation prior to pod fill

Facts of Japanese Beetle

Japanese Beetle
  • Latin name is Popillia japonica
  • Native to Japan; found in United States in 1916
  • Most damage is from adult feeding; however, the larval grub also can feed on roots
  • Late-planted fields are at greater risk
  • Japanese beetles are often found in field edges or areas of delayed growth
  • Over 300 hosts: corn, soybean, ornamentals, fruit trees, grapes, weeds
  • One generation per year
Distribution
U.S. map indicating where Japanese beetles are present
  • Well established east of the Mississippi River, the Japanese beetle is also present in most other corn and soybean growing states

Key Characteristics

Japanese Beetle

Japanese Beetle

  • One-half inch adults are shiny metallic green with bronze wing covers, with six white hair tufts on each side of their abdomen

Related Species

Masked Chafer

Masked Chafer - light color

 
Green June Beetle

Green June Beetle - twice the size, no white tufts

 
False Japanese Beetle/Sand Chafer

False Japanese Beetle/Sand Chafer - dull, no white tufts

Life Cycle

Japanese beetle annual life cycle

Management of Japanese Beetle

  • Favorable conditions
    • Adults prefer lighter soil for egg laying
    • First entry into an area is usually near transportation such as railroads or major highways
  • There are no natural enemies in the U.S.
  • IPM Practices
    • No transgenic or native gene resistance is currently available for either soybeans or corn
    • Trapping is NOT recommended as it has a tendency to attract the beetles
    • Scouting should begin in corn in July and August and switch to soybeans during August
    • Use percent pollination and presence of uncut silks as a guide when deciding treatment of corn. Leaf feeding is rarely significant in corn.
    • Use percent defoliation and amount of pod fill remaining to help decide economics of insecticide treatment for soybeans
Economic Thresholds
  • Treatment thresholds for corn insecticides:
    • Silks clipped to within ½ inch of the ear tip
    • Less than 50% of plants pollinated
    • Beetles are present and feeding
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