Leptocybe invasa Fisher & La Salle is an important pest of Eucalyptus plantations in South Africa (SA) as it causes significant reduction in growth or mortality. A trial was implemented in 2012 in Zululand (KwaZulu-Natal) to determine the effect of regeneration method (coppice vs replant) on the susceptibility of a Eucalyptus grandis x E. camaldulensis clone (GC clone) to L. invasa. The trial consisted of three treatments that were replicated four times and laid out in a randomised complete block design.
White grubs (Scarabaeidae larvae) can contribute to serious transplant mortality immediately following re-establishment. Synthetic insecticidal treatments of deltamethrin and imidacloprid are currently used in the control of white grub and other soil-borne insects of commercial forest tree species. However, the use of these insecticides has been deemed highly hazardous and is regulated by the Forest Stewardship Council (FSC). Therefore, there is an immediate need to find effective alternative products for the control of white grubs.
Sustainable timber supply from a limited land resource necessitates management practices that aim to maintain an optimal soil nutrient supply to growing trees. Research to understand management impacts on soil productivity is required to inform site-specific risk and management decisions. The effects of post-harvesting soil management operations were assessed on growth and soil properties on a low carbon, dystrophic sandy soil in the subtropical environment of the Zululand coastal ecosystem.
The first national monitoring survey of the blue gum chalcid wasp, Leptocybe invasa, in the eucalypt plantations of the summer rainfall region of South Africa was conducted between November 2016 and February 2017. One hundred and eighteen sites were surveyed for the presence of L. invasa-induced damage, damage intensity and presence of other insect pests and pathogens. Leptocybe invasa was present in 27% of sites sampled. When present, damage was predominantly of low intensity and uniformly spread, affecting most trees in the stand.
Uromycladium acaciae is a pathogen-causing disease on black wattle plantations. First discovered in 2013 near Eston in the KwaZulu-Natal Midlands, the disease has since spread throughout the wattle growing regions of South Africa and Swaziland. Symptoms are characterised by leaf deformation, defoliation, stem infection and stunted tree growth. The disease affects trees of all ages, from seedling stage to end of rotation.
Water stress at and soon after planting are major causes of seedling mortality in forestry reestablishment, even during prescribed planting windows. Planting with water (puddle planting) or with hydrogel during unfavourable moisture conditions has limited capacity to sustain adequate water supply to the plant. To ensure adequate water supply it may be beneficial to periodically re-apply water to each plant over short intervals (days to weeks) after planting. This is recommended as a standard practice in Brazil, though no literature to indicate the magnitude of the benefit was found.
Corymbia henryi has shown potential for good growth and pest and pathogen tolerance in the sub-tropical and warm temperate forestry areas in South Africa. To further expand the genetic base of this species, two trials comprising six provenances from Australia were established on the Zululand Coastal Plains in 2010. Four-year diameter at breast height measurements were performed in the trials, survival and basal area per hectare calculated, and Type B correlations estimated to determine genotype x environment interaction.
Antitranspirants are a range of chemicals and compounds applied to plant foliage aimed at lowering transpiration rates of plants under conditions that can lead to water stress. While antitranspirants have been widely tested in horticultural crops, there has been limited use in forestry applications. Where they have been tested, antitranspirants are reported to lower seedling transpiration rates under simulated stress conditions, but may lower growth rates and lead to death. There is limited evidence for cost effective in-field benefits of these products.
The Institute for Commercial Forestry Research (ICFR) held its 7th Forest Science Symposium from 18 to 20 July, at the One Life Church in Pietermaritzburg. The three-day event was co-hosted by the ICFR, the International Union of Forest Research Organizations (IUFRO), the Department of Agriculture, Forestry and Fisheries (DAFF) and other research partners.
At the time of trial implantation (11 January 1996), Fusilade® (fluazifop-P-butyl) was a registered herbicide used for the control of grasses in commercial eucalypt plantations. However, concern was expressed about young eucalypt seedling phytotoxicity from “over the top” spraying with Fusilade®, especially under hot and humid conditions. This was tested in a nursery trial using Eucalyptus grandis clonal cuttings (GC784) and Eucalyptus nitens seedlings.