Identifying and Scouting for Japanese Beetle

How to Field-Scout for Japanese Beetle (JB):

• Japanese beetle is a relatively new pest in Missouri corn and soybean fields, so scouting procedures and thresholds may be modified with experience.
• Although Japanese beetle larvae will damage crop plant roots, thresholds for insecticide application are based on feeding damage by adults.

Corn

• Although leaf feeding is possible, threshold for insecticide application is based on number of beetles present.
• Observe 10 plants in at least five places in the field.
• Count beetles and calculate the number of beetles per ear. Determine the extent of silk clipping.
• • Threshold for insecticide application is three or more beetles per ear. Do not apply insecticide if pollination is more than 50% complete (brown silks).

Soybean

• Threshold for insecticide application is based on percent defoliation, not number of beetles.
• Observe five plants in at least five places in the field. Larger fields may require additional locations.
• Estimate the amount of defoliation. Feeding often begins on leaves at the top of the canopy; do not focus solely on these leaves.
• Threshold for insecticide application is 30% defoliation before flowering (R1) and 20% defoliation between flowering and mid-pod-fill (R6).

How to Identify Japanese Beetle - Popillia japonica Newman

Identification of larvae (damaging stage)

• Larvae (grubs) live in soil and are rarely seen above ground.
• "C"-shaped larvae are creamy white with a brown head capsule.
• Immature larvae possess chewing mouthparts and three pairs of legs on the thorax.
• Maximum larvae length is about 1-inch.
• Similar appearance to other white grubs; look for the pattern of bristles on raster (hind end); Japanese beetle Larvae possess a V-shaped pattern of bristles.

• Adult beetles measure approximately 0.5 inches in length
• Metallic green with bronze-colored wing covers.
• Just below the wing covers, on each side of the abdomen are six tufts of white hair

• False Japanese beetles are similar in size and appearance to Japanese beetles, but not as shiny and not as brightly colored.
• False Japanese beetles do not have the characteristic arrangement of the six white tufts along their abdomen

Download these great resources and take it to the field!

• Scouting Japanese Beetle PDF (68 KB)

Resources

• 2011 Missouri Pest Management Guide: Corn, Grain Sorghum, Soybean, Winter Wheat
  University of Missouri Extension