Japanese Beetle
Beginner
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Scientific Name
Popillia japonica
Identification
Larvae:
- Milky white
- “C”-shaped grubs
- 2 cm in long at maturity
- Light reddish brown, 13 mm long and 6 mm wide
Adults:
- 10-13 mm long
- Metallic green to greenish-bronze, with coppery red wings and small white tufts on the sides and tip of their abdomen
- Head is brown and the body has three pairs of legs
Damage:
- Beetles feed on tissue between veins on leaves creating a lacelike skeletonized appearance
- Severely injured leaves soon turn brown and often drop
- Usually feed in groups, starting with youngest leaves and moving downward on shoots
- Fruit of early ripening peach trees may be gouged in irregular, shallow patches
Often Confused With
June Beetles and Rose Chafers ( people misidentify by name)
Period of Activity
Adults begin emerging in late June to early July, and begin feeding on suitable host plants. Japanese beetles are most active on warm, sunny days on favorite hosts. Adults enter the ground in early evening.
Scouting Notes
Adults are readily observed in orchards during regular orchard monitoring.
Thresholds
There are no thresholds for this pest.
Advanced
This pest affects:
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Scientific Name
Popillia japonica
Identification
Larvae:
- Milky white
- “C”-shaped grubs
- 2 cm in long at maturity
- Light reddish brown, 13 mm long and 6 mm wide
Adults:
- 10-13 mm long
- Metallic green to greenish-bronze, with coppery red wings and small white tufts on the sides and tip of their abdomen
- Head is brown and the body has three pairs of legs
Damage:
- Beetles feed on tissue between veins on leaves creating a lacelike skeletonized appearance
- Severely injured leaves soon turn brown and often drop
- Usually feed in groups, starting with youngest leaves and moving downward on shoots
- Fruit of early ripening peach trees may be gouged in irregular, shallow patches
Often Confused With
June Beetles and Rose Chafers ( people misidentify by name)
Biology
Japanese beetle has a host range in excess of 300 plants and has one generation per year. It over-winters deep in the soil profile as grubs that reach maturity in early spring. As frost leaves the ground, the grubs begin moving closer to the soil surface to feed briefly on roots and then pupate. After spending 3 to 4 weeks in the pupal stage, they emerge as adults. Adults emerge in greatest numbers during early July and live for up to 6 weeks, during which they spend extended periods aggregating, feeding and mating repeatedly. They are most active on warm, sunny days. A temperature of 21°C and a relative humidity of 60% are ideal for beetle flight. When temperatures exceed 35 °C and relative humidity is greater than 60%, flight ceases. Beetles can fly up to 1.6 km; even flights of 8 km have been noted with a good wind. Beetles usually feed and mate during the morning and return to the soil in the late afternoon and evening.
Females lay eggs in several small batches in grassy areas. These egg-laying episodes occur multiple times between bouts of feeding and mating. Adults enter the ground in early evening. Each female may lay a total of 40 to 60 eggs over time. Egg-laying continues until late July and August. Eggs hatch in about two weeks. Moisture is crucial to egg hatch and larval development and under dry conditions, eggs and larvae fail to develop. If there is adequate moisture, newly hatched grubs feed on fine plant roots in the upper 5-10 cm of soil. In drier or cultivated soils, grubs will be found lower in the soil profile. In September, as soils begin to cool, grubs move deeper into the soil and remain where the soil is about 10C at a depth of about 15-25 cm. In cultivated soils, this may be deeper; up to 25-30 cm.
Period of Activity
Adults begin emerging in late June to early July, and begin feeding on suitable host plants. Japanese beetles are most active on warm, sunny days on favorite hosts. Adults enter the ground in early evening.
Scouting Notes
Adults are readily observed in orchards during regular orchard monitoring.
Thresholds
There are no thresholds for this pest.
Management Notes
This is a sporadic pest of tender fruit and severity of injury may differ between adjacent blocks of different varieties. No products are registered for its control; however, products applied for other insects may have some activity.
Some information included above was excerpted from;
