During July 2004, an infestation of an unknown larval insect in ten-year and older Eucalyptus nitens was reported on the Mpumalanga highveld of South Africa. Samples of wood containing larvae were collected from the field and taken to the Forestry and Agricultural Biotechnology Institute, University of Pretoria. The adult specimens were subsequently identified by the Transvaal Museum as the native Coryphodema tristis. No records have been found of the insect on any member of the Myrtaceae. A total of approximately 3000 hectares of E. nitens, within 95 compartments greater than eight years of age on the Mpumalanga Highveld were surveyed in September 2004. The older age classes and lower elevation sites had significantly higher infestations than the younger, higher elevation sites. Low infestations are present in young stands of E. nitens (< 6 years of age), and not restricted to lower productivity sites, an indication that the pest risk potential is higher than originally anticipated.
The potential high yields of Eucalyptus shoot multiplication achieved with a temporary immersion culture system such as RITAlsupg(R)l/supg are compromised by losses caused by microbial contamination particularly bacteria, characteristic of the explants used to initiate the cultures. Disinfection of the explants through antibiotic treatments has on occasion been effective but this approach is unreliable and costly. In the present study, antibiotics were found to have only a bacteriostatic and not a curative effect. A strategy was, therefore, required to achieve uncontaminated explants via a rapid and accurate screening procedure. Of the approaches tested, that which was considered most appropriate for a commercial laboratory involved inducing bud break on a semi-solid medium, screening axillary buds for endogenous contamination on a semi-selective microbial medium and initiating RITAlsupg(R)l/supg cultures with buds identified as being microbial-free.
Extracted from text ... Southern African Forestry Journal - No. 208, November 2006 1 Guest Editorial Urban forestry - A cinderella science in South Africa? INTRODUCTION The benefits of forests (in their broadest sense) and of trees to the natural environment and rural communities are well known throughout the world, including in South Africa (e.g. see chapters in Lawes et al. 2004). The presence of these benefits has also been extrapolated to urban situations, where natural forests and veld might be left in situ, or trees planted in public spaces, or in private gardens. These benefits span the social, aesthetic, health, environmental and economic ..
This report summarises results of past research in South Africa on the wood properties and qualities of P. maximinoi, supplemented by results of a study performed recently on an approximately 15.5-year-old provenance trial at Wilgeboom after it had been severely damaged by fire. The trees selected to study wood density, branching characteristics and sawn-board quality of the species, were previously selected for further breeding for their superior volume growth and stem form. Differences in mean internodal length and mean branch diameter were statistically highly significant among provenances, on average being longer and generally thicker than those of the P. elliottii and P. patula. The bark-layer of P. maximinoi was thicker than that of P. patula but it differed little in thickness with that of P. elliottii. Provenance means in air-dry wood density varied within a relatively narrow band of 0.457 to 0.483 g/cm3, with an average mature wood density resembling closely that of P. patula. However, P. maximimoi was characterised by increased uniformity in density across its radius, as it tended to form denser wood in the central parts of its stem, causing its pith-to-bark density gradient to be flatter. Growth rate had no effect on wood density, but improved radial density uniformity was clearly associated with increased growth rate. Sawn boards were of good quality and showed little warp after drying despite the fact that some of the trees were slightly crooked, with possibly a higher incidence of compression wood. Compared to P. patula and P. elliottii this species exhibited a darker brown colour with almost a reddish tinge when freshly cut. The annual rings were hardly recognisable on rough-sawn surfaces. Wandering pith often occurred in some boards as a result of the higher degree of stem crookedness. Since the branches of P. maximinoi tend to be arranged in whorls, it can be expected that the impact of knots on the strength of the sawn boards would predominantly be the result of the combined effect of knots grouped together, rather than individual knots. This is also a valuable attribute, as the species lends itself to the production of relatively long knot-free board sections from the unpruned parts of the stem, which would enable manufacturers of finger-jointed products to increase the volumes and diversity of their products, especially where appearance is important. Loose knots occurred more frequently in boards cut from P. maximinoi compared to the two controls, most likely as a result of pruning that was carried out too late considering the fast growth of the species.
