N. G. Collett

The control of sirex wood wasp using biological control agents in Victoria, Australia.

1 The sirex woodwasp, Sirex noctilio has been a significant pest of radiata pine plantations in Victoria since 1961. Outbreaks are usually associated with susceptible trees being under some form of stress including the effects of drought and overcrowding.

Effects of two spring prescribed fires on epigeal Coleoptera in dry sclerophyll eucalypt forest in Victoria, Australia

Abstract The cumulative effects of two low-intensity prescribed fires, applied within 3 years during spring (15 October 1985 and 3 November 1988), were assessed on families and species of surface-active Coleoptera (beetles) in litter of dry sclerophyll mixed eucalypt forest over a 5.7 year period between 26 March 1985 and 26 November 1990. The study was based on 13925 adult specimens, representing 31 families and 105 species, of which 70 species (66.7% of total) are undescribed. The most commonly trapped ‘major’ families were the predominantly predatory Staphylinidae and the decomposer/fungus feeding Nitidulidae and Leiodidae. The specimens were contained in 2240 pitfall trap samples collected from a burnt and an unburnt (‘control’) site adjacent to each other within a 30.7 ha study area. The two fires had no discernible cumulative effect on the activity of the Nitidulidae, the Leiodidae, the pool of 28 rarely trapped ‘minor’ families and the totals of decomposers/fungus feeders. However, short bursts in activity occurred among the first three of these taxa/groups during periods between the two fires. In contrast, activity of the Staphylinidae, the most abundant of all taxa trapped, declined significantly after the second fire relative to pre-first fire levels. This trend accounted for the observed reductions in activity of total Coleoptera, of total predators and of the proportions of Coleoptera in total arthropods. Family and species richness of the Coleoptera remained unchanged following the fires. An undescribed fungus-feeding lathridiid (Aridius sp.) incurred a short upsurge in activity after the second fire. As only activity (and not diversity and taxon richness) of the Staphylinidae was affected by the fires, it is expected that they will return to pre-fire activity levels when the forest recovers in the absence of further fires. Two short-rotation low-intensity spring fires can therefore be applied in the forest type studied without causing unacceptable adverse impacts on litter-frequenting Coleoptera.

Biology and control of psyllids, and the possible causes for defoliation of Eucalyptus camaldulensis Dehnh. (river red gum) in south-eastern Australia - a review

Summary Psyllids are one of the most devastating insect pest groups in Australia, affecting both native forests and eucalypt plantations. They feed on a wide variety of eucalypt host species, with some psyllid species restricted to a single eucalypt host species or to a group of closely related species. Predominant amongst eucalypt species attacked by psyllids is Eucalyptus camaldulensis Dehnh., an important tree species for a variety of reasons including the insect and decay resistance of the timber, its role in reducing water table levels and minimising erosion along streams and rivers, its adaption to soils with significant salt content, and its importance as a habitat for native wildlife. In recent years it has become a candidate species for plantation forestry, especially in the northern irrigation areas of Victoria. This paper briefly examines the biology of psyllids, covering their identification, description and life-cycles, and providing a brief history of major psyllid outbreaks in Australia. The potential for attack, levels of defoliation and subsequent impact on tree growth and tree health are also examined. Options for control of psyllids are discussed to enable landholders and forest plantation managers to make more informed decisions on ways of dealing with outbreaks on eucalypts, particulary E. camaldulensis.

Forest health surveillance in Victoria

Summary Forest health surveillance (FHS) has been undertaken in Victorian native forests and plantations on an ad hoc basis since the early 1960s in response to incursions and outbreaks of native and introduced insect pests and plant pathogens, such as sirex wood wasp, Monterey pine aphid, Phytophthora dieback, phasmatids and other defoliators. The purpose of surveillance is to provide a broad overview of forest health and data for land managers to allow them to take appropriate strategic decisions and manage risks to their estate. Early targeted FHS in Victoria consisted mainly of drive-through surveys with aerial surveillance where required to determine the extent of a particular damaging agent. In 1991, a plot-based surveillance system targeting high-risk sites was developed to monitor levels of Dothistroma disease. These plots were used to trigger more intensive surveillance (e.g. aerial) to enable early management intervention once the levels reached predetermined thresholds. In 2001, a broader plot-based monitoring system was implemented for HVP Plantations as part of its risk management program to determine the status, changes and trends in tree health on an annual basis, and provide data for management decisions to control outbreaks threatening the health of plantations. This paper describes the establishment of a plot-based monitoring system, combined with supplementary surveys to provide information on the extent and damage potential of pest agents in the HVP Plantations estate, and its possible application in native forests.

The Sirex wasp and its biological control in plantations of radiata pine variably defoliated by Dothistroma septospora in north-eastern Victoria.

Summary The distribution and severity of pine needle blight disease (PNB), caused in spring 1989 by an outbreak of the needle cast pathogen Dothistroma septospora, was assessed within a 10 km radius of two study sites near Myrtleford in the Wangaratta Pinus radiata plantation complex of north-eastern Victoria. Areas of severe needle cast were located on colour aerial photographs in spring 1989, then checked by ground survey for the percentage of visible crowns infected. Population levels of the Sirex wasp (Sirex noctilio), rated in terms of the cumulative percentage tree mortality induced by the wasp since 1989, were estimated in autumn/winter 1991. Twenty-one unthinned plots, each of 400 trees aged 14–15 years, were examined for S. noctilio and associated symptoms of D. septospora. The effectiveness of parasitoids was evaluated in the laboratory by monitoring total insect emergents from 222 billets (0.8 m long), cut in winter 1991 from 100 herbicide-injected ‘Sirex’ trap trees. All emergents of S. noctil...

A History of Forestry Education in Victoria, 1910-1980

Summary In 2010 it will be 100 years since the School of Forestry Creswick opened and accepted its first student intake. It is timely that in its centenary year the history surrounding the creation of Creswick as a centre for forestry education in Victoria is examined from the perspective of the development of forestry studies in a tertiary environment. This paper examines some of the events, issues and personalities that shaped forestry education in Victoria from the schools commencement in 1910 up to 1980 when The University of Melbourne and Creswick School of Forestry courses combined within the university sphere. Early issues surrounding the choice of Creswick as the schools location and the move to establish the Australian Forestry School in Canberra and its impacts on Creswick and state-federal relations are discussed. Personalities and events involved in shaping forestry education at the time included C.E. Carter and Dr Frank Moulds, both Principals at Creswick, Charles Lane Poole, Principal of the Australian Forestry School and John Chinner, head of forestry at the University of Melbourne, and the organisational and political context in which they operated. Links between Creswick School of Forestry and the University of Melbourne began at the schools establishment when A.J. Ewart, Professor of Botany at the University of Melbourne, was appointed Chairman of the Board of Examiners to oversee the science-based curriculum, ensuring it met university standards, and culminated in 1980 when the courses at the two institutions were combined. Reflections on the major issues discussed assess these issues and events as potential major factors that significantly affected forestry education in Victoria.

Managing insect pests in Eucalyptus globulus (Labill.) plantations in Victoria using insecticide tablets at establishment

Summary We studied the effects of fertiliser and insecticide delivered by tablets on defoliation and growth of Eucalyptus globulus in plantations near Meredith in west-central Victoria to determine whether improved foliage retention and growth were conferred by the insecticide and/or fertiliser components of the tablet. Trees at the study site were variably defoliated by three species of insect from March 2004 to September 2005. In the first year of the study, treatments containing imidacloprid insecticide had significantly less defoliation in both the upper and lower crowns than did treatments containing no insecticide. Treatments containing both insecticide and fertiliser showed increased height growth, most likely as a result of a combination of increased levels of available nutrients and protection from defoliating insects provided by the tablets leading to increased overall vigour. The tablets appear to provide adequate protection to trees for about 1 y after planting, although some protection seems to have remained until the 1.7 y assessment. Further observation is required to determine how long this protection lasts. The implications of the study are significant for eucalypt plantation managers. The application of insecticide and fertiliser in tablets at the time of planting potentially provides a more effective and environmentally safer method of insect control than traditional broadscale insecticide applications during the establishment phase. This could potentially lead to improved growth, yield and general health in the longer term.

Effects of fire retardant on heathland soils in south-eastern Australia

A study was undertaken to assess the effects of fire retardant application, unmodified by heat of fire, on soil properties in 2 fire-prone heathland communities at Marlo and the Grampians in south-eastern Australia. Fire retardant (Phos-Chek D75-R at 0.144 g/L) was applied at rates of 0.5, 1.0, and 1.5 L/m2 and compared with control treatments of nil and 1.0 L/m2 of water. Monitoring of surface soils showed that pH at both sites decreased while soil salinity increased immediately after application followed by a rapid decline to pre-treatment values within 12 months. The impact of retardant on total carbon and nitrogen was minor and within the range of natural variation of C and N in surface soils at both sites. Levels of readily available or labile forms of N increased at both sites but declined rapidly to background values after 12 months. Applications of retardant progressively increased extractable P in the surface soil at Marlo, in contrast to the Grampians where a rapid increase was observed after two months followed by a decline after 12 months. These results showed a significant increase in labile P in the surface soil after 12 months and also indicated that a large proportion of the phosphate applied had leached into the subsoil. Likewise, fire retardant applied at the highest rate caused increases in labile sulfate after 2 months at both sites, followed by a rapid decline to background levels. It is expected that the elevated levels of soil phosphate in particular could have a long-term impacts on growth and composition of heathland vegetation known to be sensitive to elevated levels of phosphate in soil.

Effect of fire retardant application on heathland surface-dwelling invertebrate communities in Victoria

Summary The effects of the application of fire retardant at varying rates on surface-dwelling invertebrates at ordinal and sub-ordinal level in heathland communities were assessed over a one-year period from March 2001 to March 2002. The study was conducted at two sites, one in East Gippsland at Mario and the other in the Grampians region of south-western Victoria where a total of 136 190 specimens representing 30 ordinal and sub-ordinal taxa contained in 5400 pitfall trap samples was collected. It was concluded that despite the application of fire retardant at varying rates, there was no significant effect on invertebrate activity at ground level amongst the ordinal groups Acarina and Dermaptera. These ordinal groups appear to form a stable component of the heathland invertebrate community at both sites. Although significant changes were observed in other major taxonomic groups (total taxa, total insects, total non-insects, Araneae, Collembola, Coleoptera and Diptera) these changes were confined to either increased or decreased activity within a single plot and were judged to be not representative of treatment. While a significant change in activity was recorded for Formicidae at both sites, this was also due to single-plot variations in activity across different treatments. Such information indicates that any significant changes observed in invertebrate activity appeared to be due to site-related environmental factors rather than the effects of the retardant itself. When assessed in terms of general diversity, taxon richness and community evenness, ordinal and sub-ordinal taxa were unaffected by retardant application at the Mario site. Significant changes in insect diversity at the Grampians site were again due to site-related factors rather than retardant effects. Further study is required to determine whether this stability is reflected at family, genus and species level, and if there are any seasonal and longer-term effects of retardant application. The combined effect of fire and retardant on invertebrate communities also requires further study.

Insect Defoliation of Mixed-species Eucalypts in East Gippsland

Summary Ground surveys were conducted in the coastal and inland mixed—species eucalypt forests of East Gippsland from 2003 to 2006, using ten permanent forest health assessment sites across the region, to determine the cause, extent and severity of extensive defoliation first observed in late 2003. The primary cause of defoliation in the 2003 and 2005 outbreaks were Doratifera spp. (cup moth) and Uraba lugens (gumleaf skeletoniser) respectively. Eucalyptus globoidea (white stringybark) and E. elata (river peppermint) appeared most susceptible while E. cypellocarpa (mountain grey gum), E. obliqua (messmate) and E. sieberi (silvertop) were generally more resistant to defoliation by these insect species. The initial assessment in November 2003 indicated high levels of defoliation with a mean of 71% (range: 30–85%) across all ten sites. Re-assessment of the sites in March 2004 indicated active defoliation had ceased and that foliage cover in the trees had improved with mean defoliation of 34% (range: 15–60%), an improvement of 37%. Subsequent defoliation late in 2005 was not as severe as the 2003 outbreak, with mean defoliation in November 2005 being 23% (range: 10–40%) across all ten sites. Re-assessment in March 2006 indicated that active defoliation had ceased and that levels of foliage cover in the trees had increased over the 2005–2006 summer, with mean defoliation of 17% (range: 10–30%) recorded, an improvement of 6%. Rather than being considered as one continuous outbreak by a single pest species, the two defoliation episodes should be regarded as separate events caused by separate insect species, although their cause(s) may have foundation in similar conditions. The U. lugens outbreak can be reliably linked to low rainfall in the region. The cause of the outbreaks by Doratifera spp. is uncertain because of insufficient knowledge concerning their lifecycle. While climatic factors are likely triggers, other factors such as eucalypt host susceptibility, foliage nutritional status, altitude, forest type, soils and geology may also influence the occurrence of Doratifera spp. outbreaks. Further, it still has to be determined whether the factors that trigger outbreaks affect Doratifera spp. directly or reduce parasitoid/predator populations that usually keep Doratifera spp. populations in check. As little is known of the predisposing factors for outbreaks (especially for Doratifera spp.), the appropriate nature and timing of any potential control measures are difficult to identify. Continued monitoring of all potential damaging insect pest populations and associated canopy cover is recommended as part of a structured forest health surveillance system in order to predict outbreaks and allow appropriate contingency plans to be made if required. However, as most native insect outbreaks in native forests are short term and part of the normal forest ecosystem, the implementation of control measures is usually not required. The potential for long-term effects of drought to increase outbreak frequency and subsequently affect tree growth and health should not be discounted, thus emphasising the need for regular monitoring.