No abstract

The primary symptoms associated with Fusarium circinatum infection in pine seedling nurseries are root and collar rot, shoot and tip die-back and seedling mortality. Management of this pathogen in nurseries usually involves the integration of various strategies relating to sanitation, insect control and fungicide treatment. The overall goal of this study was to use quantitative real-time PCR (qPCR) to detect and quantify the airborne inoculum of F. circinatum in a commercial pine seedling nursery. For this purpose, an existing qPCR method was optimised and evaluated for its efficacy to quantify and monitor airborne conidia over a one-year period. Results showed that F. circinatum occurred at relatively low levels in the nursery throughout the year and that its distribution was spatially sporadic. The data suggest that standard nursery sanitation practices in the test nursery maintained the airborne inoculum of F. circinatum at low levels. The uneven distribution of infection also suggests that airborne inoculum does not represent the primary source of inoculum for the F. circinatum-associated seedling disease.

No abstract

On the Usutu plantation the sustained production from successive Pinus patula rotations has been a focus of active research for nearly 50 y. On 13% ofthe plantation, underlain by gabbro rocks, a 20% growth decline was reported between first (I R) and second (2R) rotations as a result of developing phosphorus (P) and potassium (K) deficiencies. The operational application of fertiliser containing 75 kg P ha-1 and 75 kg K ha-1 corrected the decline in yield. In 1989 P and K fertiliser was randomly applied, at the above rate, to one half of each of a number of trial plots in a 6-y-old, 3R crop. A 4R trial was re-established on the exact location of the former 3R trial during 1999. In 2004 intensive sampling was conducted to ascertain the influence ofthe residual fertiliser on the nutrient content of the foliage, forest floor and topsoil in the 4R crop. Fifteen years after the initial fertiliser application, 0.5 M H 2 SO 4 extracted Pinorganic + P organic in the topsoil was still 41 kg ha-1 higher in the fertilised plots than in the control plots. The total forest floor mass was not affected by the residual fertiliser, although the mass of the partially and fully decomposed forest floor litter increased by 3.5 t ha-1 (l 0% level). The residual fertiliser increased the P concentration in only the various needle components and had no effect on any other components or nutrients in the organic matter. We conclude that residual P fertiliser had a greater effect on foliar, forest floor and soil nutrient content than residual K fertiliser.

No abstract

Fusarium circinatum is an important fungal pathogen of Pinus species. In South Africa, it is the most significant pathogen of Pinus patula seedlings in forestry nurseries where it presents a substantial constraint to productivity and can continue to cause mortality in-field for up to two years after establishment. This study describes the results from two trials where P. patula seedlings were inoculated with F. circinatum to determine the impact of the pathogen on nursery and field performance. Seedlings were also subjected to water stress treatments to ascertain whether this would trigger the onset of disease symptoms. Inoculum load and timing of inoculation had significant effects on seedling survival in both the nursery and field. High inoculum concentrations caused greater levels of mortality and, where seedlings were inoculated at a young age, they showed higher levels of susceptibility to F. circinatum. Temporary water-stress in the nursery produced smaller plants and improved in-field survival, but this treatment did not trigger higher mortality in inoculated treatments. On the other hand, transplant stress was a major contributor to the higher levels of mortality observed in inoculated treatments. Overall, these studies confirmed that infection in the nursery leads to the disease problems observed during early plant establishment in the field.

No abstract

The development of a plantation eucalypt wood-based forest products industry in South Africa is outlined. Forest research that has contributed to increasing wood production from the ultimately finite land resource available for industrial plantations is reviewed. The application of this technology to eucalypt plantations by Sappi Forests is described and evidence for resultant increased wood production is presented. Improved silviculture, introduction of alternative species and deployment of genetically superior planting stock coupled to site classification and site-specific application of these technologies have all contributed to measured gains. The continued development and application of appropriate forest technology will be critical to a sustainable future for the industry in South Africa. Issues pertaining to this are discussed.