Management of Hylastes ater (Coleoptera: Scolytidae) attacking Pinus radiata seedlings

This study investigates the biology and ecology of the black pine bark beetle, Hylastes ater Paylcull, attacking young Pinus radiata D. Don, during the period 1994-1997. Aspects of the life history and ecology of the black pine bark beetle were studied under laboratory and field conditions and results incorporated into the development of a pest management strategy. H. ater has three distinct generations during the year, with mature adults emerging November-January, March-April, and August-September. Following emergence, adults cause extensive damage and often death to the seedlings, in their search for suitable breeding sites. H. ater has caused significant economic damage to second rotation plantations of P. radiata seedlings in the Plenty Valley of Southern Tasmania since 1990. Physical, chemical and microbial aspects of the host selection and attraction behaviour of H. ater were investigated involving identification of several primary and secondary attractants. Physical aspects involved in the attack of H. ater, including bark thickness, depth of attack, spatial location, position and condition of host material were studied under field conditions. Chemical aspects included field experiments and laboratory bioassay of host related volatile compounds and a range of compounds which have been reported as sex attractants or repellents in or to other bark beetles. This included the isolation of volatiles occurring within adult beetles at different stages of their development and analysis of feeding beetles and P. radiata host material over a period of time. Bacterial, yeast and fungal species associated with adult beetles were isolated, identified and both field experiments and laboratory bioassays conducted to evaluate any potential role in beetle behaviour. Parasitic nematodes associated with H. ater were isolated and identified. Results were examined with regard to past and current management practices and recommendations made for reducing the future pest status of H. ater. Firstly, the control and management of H. ater must be based on reducing the incidence of attack on stumps, logging slash and seedlings. This can be achieved by eliminating the soil-bark interface and reducing the moisture content of slash and stumps by slashing or chipping practices. Secondly, thorough planning of harvesting operations should be conducted to ensure large amounts of slash do not build up in adjacent areas. Thirdly, monitoring of future second rotation planting coupes should be conducted prior to site preparation and establishment to determine the likely risk of H. ater attack.