Ecological studies on the horizontal or black borer Austroplatypus (= Platypus) incompertus (Schedl) (Coleoptera : Platypodidae) in forests of south-eastern Australia.  J.A. Harris, K.J. Campbell and G. McK. Wright.  February 1973.  22 pp. (unpubl.)

SUMMARY

The ambrosia beetle Austroplatypus incompertus (Schedl) was described in 1968 as Platypus incompertus n.sp. by Schedl, but Browne proposed name Austroplatypus for the genus in 1971. The beetle occurs over a wide area of eastern Victoria and south-eastern New South Wales and has been recorded in 13 eucalypt species, including some of commercial importance.

Studies of the distribution of attacks, host species, structure of galleries, and activity within these galleries were undertaken. These studies show that the galleries are initiated only in the rough bark on the trunk of host species. From one external opening the gallery may form a multi-branched system of tunnels extending deep into the heartwood, but each gallery remains in one plane perpendicular to the axis of the tree. Many galleries may be present in one tree but no connecting tunnels have been observed.

The life cycle is long, at least four years, and individual galleries may be maintained continuously for at least 36 years. The insect initiates galleries only in standing trees but if trees containing active galleries are felled, beetles may emerge from these trees four years after felling.

Timber of trees containing galleries of A. incompertus may be degraded by the presence of: (1) pinholes (2) black stain on tunnel walls (3) flat sheets of black stain across large galleries (4) streaks of black stain parallel to the axis of the tree (5) brownish stain discolouring large sections of the log, and (6) lines of weakness, caused by the wood rotting fungus, wherever galleries occur. Economic loss is incurred since timber degraded by the beetle is converted to lower grades of output.

Peak emergence of young adults occurs in March and April, but emergence may be observed at any time. The number of young adults which emerge from a gallery within a year is variable, but 84 have emerged in a year from a gallery in Eucalyptus delegatensis Baker.

Occlusion of the gallery by kino produced by the host tree was the major cause of colony mortality throughout the period of study. The majority of galleries become occluded within 1 or 2 years after initiation, and do not produce a second generation.

At present there is no easy method of control. Live trees remaining after a logging operation are a source of infestation of the next crop, and if these trees are removed, the chance of attack in the future stand is reduced. Location of coupes, and methods of regeneration are discussed as useful preventative measures.

Also published:

Harris, J.A., Campbell, K.G. and Wright, G. McK. (1976)  Ecological studies on the horizontal borer Austroplatypus incompertus (Schedl) (Coleoptera : Platypodidae).  J. Aust. Entomol. Soc. (N.S.W.) 9: 11-21.