japanese beetles
Beginner
Scientific Name
Popillia japonica
Identification
Eggs
- Laid in soil, in quantities from 1 to 4
- 2 cm long, C-shaped
- Milky white with a brown head and three pairs of legs
Adults
- Shiny metallic green body with copper coloured wings
- Small white tufts on the sides and tip of their abdomen
Injury
- feed on the upper surface of young succulent foliage
- chew the tissue between the veins and creating a lacy appearance
Often Confused With
Eight spotted spotted forester damage - entire leaves or the interveinal areas of leaves are chewed and webbing may be present on leaves
Climbing cutworm damage - complete defoliation except for main veins occurs early in the season
Period of Activity
Adults start to feed around pea-size berry (late-June or early July) and feed well into August in some years.
Scouting Notes
Adults emerge around the time that Canada thistle, chicory and Queen Anne's lace bloom. Damage to wild grape is a good indicator of beetle feeding. It has been noted that after emergence, adults will feed on shorter plants first, for example weeds, and then move to taller plants later in the season. Beetles will drop from foliage if disturbed.
Monitoring traps baited with a floral lure (for females) and a sex pheromone (for male) are highly efficient for attracting beetles. These traps are not recommended as monitoring or management tools because they attract more beetles into the area than are caught. It is not uncommon to see beetles overflowing traps in heavily infested areas which may result in higher levels of localized damage. The best way to monitor for Japanese beetle in grapes is to go out and look for them during routine scouting-they are conspicuous daytime feeders.
Threshold
There are no established thresholds for this pest. Vines can tolerate some leaf area loss without impacts to growth. Tolerance for feeding damage on leaves depends on the health of the vine (growth stage, crop level, weather stresses) and the presence of other foliar pests. In years of vigourous growth, vines will tolerate more feeding.
Advanced
Scientific Name
Popillia japonica
Identification
Eggs
- Laid in soil, in quantities from 1 to 4
- 2 cm long, C-shaped
- Milky white with a brown head and three pairs of legs
Adults
- Shiny metallic green body with copper coloured wings
- Small white tufts on the sides and tip of their abdomen
Injury
- feed on the upper surface of young succulent foliage
- chew the tissue between the veins and creating a lacy appearance
Often Confused With
Eight spotted spotted forester damage - entire leaves or the interveinal areas of leaves are chewed and webbing may be present on leaves
Climbing cutworm damage - complete defoliation except for main veins occurs early in the season
Biology
Japanese beetle 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. Lack of snow cover may increase larval mortality.
Japanese beetles have a host range in excess of 300 plants. Preferred plants for adult feeding are grape, early apples, cherry, peach, plum, raspberry, woody ornamentals, rose, zinnia, linden and corn. Adults are highly attracted to grape vines and when Japanese beetle adults appear in large numbers, extensive defoliation can occur.
Period of Activity
Adults start to feed around pea-size berry (late-June or early July) and feed well into August in some years.
Scouting Notes
Adults emerge around the time that Canada thistle, chicory and Queen Anne's lace bloom. Damage to wild grape is a good indicator of beetle feeding. It has been noted that after emergence, adults will feed on shorter plants first, for example weeds, and then move to taller plants later in the season. Beetles will drop from foliage if disturbed.
Monitoring traps baited with a floral lure (for females) and a sex pheromone (for male) are highly efficient for attracting beetles. These traps are not recommended as monitoring or management tools because they attract more beetles into the area than are caught. It is not uncommon to see beetles overflowing traps in heavily infested areas which may result in higher levels of localized damage. The best way to monitor for Japanese beetle in grapes is to go out and look for them during routine scouting-they are conspicuous daytime feeders.
Threshold
There are no established thresholds for this pest. Vines can tolerate some leaf area loss without impacts to growth. Tolerance for feeding damage on leaves depends on the health of the vine (growth stage, crop level, weather stresses) and the presence of other foliar pests. In years of vigourous growth, vines will tolerate more feeding.
Management Notes
Japanese beetle adults show feeding preferences for different grape cultivars, in particular those with thin, glossy and tender foliage. Mature grapevines are able to tolerate some defoliation without delaying ripening or reduced fruit yield and quality.
With the prolonged period of activity and multiple sources of adults from the landscape (homes, gardens, vineyards, orchards, roadways etc), re-infestation may occur following treatment.
Management with insecticides - Control measures are usually needed only in selected areas each year. Insecticides may be used to control Japanese beetles if necessary. See OMAFRA Publication 360, Fruit Crop Protection Guide - Chapter 4 Grapes : Recommendations for japanese beetles at Immediate post bloom through fruit set. Suppression of Japanese beetles may occur when sprays for second-generation grape berry moth are applied.
