Five-spined bark beetle

• Adult beetles are dark red-brown to almost black.
• 3–5mm long.
• May be shiny or dull, hairless or densely covered with hairs or scales.
• The margin of their rear section has five spines on each side.
• Signs of an infestation are small accumulations of fine frass on the surface and in crevices of the bark.
• See more images of Ips grandicollis from the Pests and Diseases Image Library (PaDIL).

Similar species

I. grandicollis is similar in size, colour and shape to several species of bark beetles. It can also coexist with other bark beetles within the same phloem tissue of the same tree.

In Queensland

Two similar species that mainly attack the stumps or roots of dead trees, thinnings and prunings on the ground, or areas of debris from tree clearing or harvesting are:

• golden haired bark beetle (Hylurgus ligniperda)
• black pine bark beetle (Hylastes ater).

Overseas

A number of bark beetles are destructive forest pests, posing significant biosecurity threats to Australia:

• southern pine beetle (Dendroctonus frontalis)
• mountain pine beetle (D. ponderosae)
• western pine beetle (D. brevicornis)
• red turpentine beetle (D. valens)
• European spruce bark beetle (Ips typographus)
• pine shoot beetle (Tomicus piniperda).

Widely distributed throughout Queensland's plantations of exotic pine and the tropics since 2009.

• Pinus species, including commercially grown exotic pines (and hybrids):
  • slash pine (P. elliottii)
  • Caribbean pine (P. caribaea var. hondurensis)
  • radiata pine (P. radiata)
  • loblolly pine (P. taeda).
• Dead and living standing trees, logs and harvest debris are all affected.

• Can build up damaging numbers in thinnings and harvest debris.
• Also attacks living trees if they are fire-damaged or stressed.
• Needles begin to turn red above the site of attack and later the entire crown turns red and then brown. The bark becomes riddled with 1.5mm emergence holes.
• Carries blue stain fungi, which can affect the value and aesthetic quality of milled timber.
• Populations in Australia have caused large-scale mortality of drought-stressed pine trees.
• At Beerburrum, Queensland in 1994, this pest caused $10 million in destruction to fire-damaged trees.
• In southern Australia, 'feeding attacks' by newly emerged adult beetles have been recorded in young plantations adjoining areas of cleared trees.
• See high-resolution images of Ips grandicollis damage.

• Adults bore into the outer bark of trees or woody debris (slash). Clusters of males produce a chemical pheromone that attracts more beetles to the attack site.
• Males initially form a nuptial chamber in the bark, and typically admit 3-5 females.
• Females excavate long tunnels in the phloem (food conducting tissue, just under the bark), shaped like tuning-forks.
• Larval tunnels, tightly packed with frass (waste) fan out from the main tunnel.
• Larvae pupate in chambers constructed in the bark.
• Newly-emerged adults feed briefly under the bark before emerging and restarting the cycle.
• Four or more generations are achieved per year in south-eastern Queensland, which means that populations can increase rapidly with favourable resources.
• I. grandicollis and its attendant mites carry and spread spores of blue-stain fungi, which grow in the tree sapwood and phloem.
• Some fungi associated with bark beetles (Ophiostoma and Ceratocystis spp.) have evolved symbiotic relationships with the beetles and the mites that live on them. These associations of organisms act together to overcome the defence mechanisms of living trees. The fungi benefit by being transported to new susceptible host trees by the beetles and the developing beetles and mites benefit from using the fungi as a source of nutrition.

• Control is effected by 2 introduced biological control agents, the parasitoid wasps Roptrocerus xylophagorum and Dendrosoter sulcatus.
• Use appropriate harvesting practices, for example, reducing debris and removing logs quickly off-site.
• Prompt salvage harvesting after natural disasters like fires or windstorms may also help contain population growth.
• Debarking wood prevents the introduction of bark beetles. This can reduce populations and minimise blue stain damage to logs if done promptly.
• Insecticides and deterrents have limited use due to the cost of application and degree and duration of protection. They are used only rarely in the forest setting, e.g. for protecting high value trees.
• This beetle may also interfere with the monitoring and control program for sirex wood wasp by attacking sirex trap trees, preventing wood wasp attacks and reducing the program's effectiveness. Research is underway to find ways to manage this problem.

• Australian Pesticides and Veterinary Medicines Authority (APVMA)
• CABI, 2022, Ips grandicollis (Five-spined bark beetle), In: Invasive Species Compendium. CAB International, Wallingford, UK.
• Stone, C, Simpson, JA. 1991, Effect of six chemicals on the insects, mites, nematodes and fungi associated with Ips grandicollis (Eichhoff) (Coleoptera: Scolytidae) in northeastern New South Wales,  Journal of the Australian Entomological Society, 30:21-28.