PEST

NAME
Japanese Beetle
Popillia japonica

ORDER
Coleoptera

Description of the Pest
The adult beetle has an iridescent bluish-green body with streaked grey, wing cases and is up to 12mm long. The eggs are laid in lawn or grassy areas where the small larva feed. Both adult and larva have chewing mouth parts. The insect originated in Japan and was introduced into eastern USA and southern Canada.
This insect has a Holometabolouslife cycle, ie. When metamorphosisis observed during the pupalstage.


Image by Ohio State University

Period of Activity
The adult is active and the eggs are laid from summer to autumn although the female adult normally lays its eggs in the first seven to ten days of its life.

Life Cycle
The tiny white eggs are up to 1.5mm long and are deposited on the soil where they can absorb moisture. After hatching the whitish larvae are a typical curl grub and identified by a serious of bristles in a 'V` shape on its raster. There are three larva stages with the mature larvae growing to 32mm long, then pupate in the soil. The pupa is cream at first becoming red-brown and growing to 14mm long. Adults are oval shape, metallic green 10mm long by 7mm wide with brownish wing covers and five tufts of whitish hairs on either side of the abdomen.

Adult beetles emerge in early summer and find a suitable host plant to feed on, and then release an odour that attracts other emerging beetles to that plant. The females attract the males by emitting a pheromone and matting can occur on the host plant or on the ground. Fertilised females burrow into the soil up to 100mm to deposit up to five eggs then returning to the host plant and mate again. During the summer period the female deposits up to 60 eggs and under hot conditions the eggs can hatch within nine days. Under cooler conditions it can take up to thirty days for the eggs to hatch. Emerging larvae feed on the roots of the host plant.

Damage Caused
The adults skeletonize leaves and chew on buds or flowers, sometimes completely defoliating the host plant. The skeletonised leaves soon wither and die. Turf grass becomes spongy under foot as a result of tunnelling and the grass has a withered appearance in irregular patches that will not respond to watering. On inspection by lifting the turf numerous larvae can be found feeding on the roots.

Susceptible Plants
There are many broad leafed plant species that are attacked including fruit, vegetables and ornamental plants. Roses are badly affected and may have up to 50 adults on a single bloom.
The larvae attack the roots of Turf Grasssuch as Poa pratensis(Kentucky Bluegrass), Lolium perenne(Perennial Ryegrass), Festuca arundinacea(Tall Fescue) and Agrostis palustris(Bent).

Many trees are particularly susceptible to attack and should not be plantedaround turfed areas such as golf courses. These include; Acer palmatum(Japanese Maple), Acer platanoides(Norway Maple), Quercus palustris(Pin Oak), Aesculusspecies (Horse Chestnut), Hibiscus syriacus(Rose of Sharon), Platanus occidentalis(American Sycamore), Prunus cerasifera(Cherry Plum), Prunus x blireana(Blireana Plum), Prunus campanulate(Taiwan Cherry), Prunus x yedoensis(Tokyo Cherry), Rosa species, (Rose), Salixspecies (Willow), Tiliaspecies (Linden) Ulmusspecies (Elms) and Parthenocissus quinquefolia(Virginia Creeper).

Vitis, Alcea, Zinnia, Hibiscusand Dahliaspecies are also attacked.

Cultural Control
It is difficult to control infestations of Japanese Beetles, but certain measures such as keeping soil dry during the first larval stage or avoid planting trees that are susceptible to beetle attack around lawn areas will help. Small infestations may be removed by hand during the early morning and small crops may be covered in netting for protection.

BiologicalControl
There is no effective natural control, but certain species of parasitic wasps help control. Soils may be infected by Bacterial Milk Disease which after a couple of years can be efficient in controlling larvae, but infected areas should not be sprayed during this period as this may kill off the bacterium.

Chemical Control
Smaller plants may be sprayed with a contact insecticide when the insect is first seen or turf areas can be sprayed with a systemic chemical.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.