Polyphylla spp. (Scarabaeidae)

the common June beetle

Adults:

Note compact form of adult, and lamellate antennae characteristic of Scarabaeidae. Tarsi are long and the tibiae often display a "toothed" margin. This is not the injurious stage, although the usual food of adults is foliage of trees, they are not important in that respect. Adults "hiss" (stridulate) when disturbed or distressed.

Larvae:

Commonly known as "white grubs". These ivory coloured larvae usually lie in a curled position. They have 6 prominent legs, well formed for digging, not walking. The head is brownish and armed with a powerful pair of mandibles. White grubs vary in size from 5 mm when first hatched to over 2 cm when fully grown. Bacteria in a large hindgut caecum break down plant material. Through proctodeal feeding, these bacteria are ingested and digested by the grub as a protein source.

Damage:

White grubs are subterranean in habit, feeding on the roots of young plants. Damage can be detected when seedlings turn sorrel red and die as a result of larvae shearing off the plant roots. Larvae generally live for 2 years, doing the greatest damage in their second year.

Principal Hosts:

Many conifers, including hemlock, Douglas-fir, spruce and pine.

Economic Importance:

Larval damage to seedlings in nurseries has been recognized as a problem for over 50 years. Not until the 1940's did it become evident that grubs might also be a threat to forest plantations.

References and Links:

FC: 250-251.

See Diseases and Insects in British Columbia Forest Seedling Nurseries.

Additional Images: