Differences in pit size (dimensions/volume), pit quality (soil friability and uniformity) and tree performance (height, groundline diameter, survival, biomass index (corrected) adjusted for survival) were assessed, with results up to one year presented. Dimensions of pits and pit soil friability for the two pitting treatments were different, but pit volumes were similar (manually prepared pits = 4.7 L; motor-manually prepared pits = 4.4 L). Differences in pit soil moisture content were detected between dry planting (4.1%) and all other treatments (9.9%), which received water.
The second national monitoring survey of the blue gum chalcid wasp, L. invasa, in the eucalypt plantations of the summer rainfall region of South Africa was conducted between February and November 2018. One hundred and thirty-four sites were surveyed for the presence of L. invasa induced damage, damage intensity and presence of other insect pests and diseases. L. invasa was present in 24.7% of sites sampled. This result shows a slight reduction in the presence of L. invasa’s induced damage from the previous survey conducted in 2017, when damage was observed in 27% of sites.
In KwaZulu-Natal, white grubs are dominant soil pests that can contribute to serious transplant mortality at re-establishment. A two-year monitoring programme was initiated in summer 2017 to determine temporal trends of white grub activity. From February 2017 to January 2018; six sites planted to pine, eucalypt and wattle and located in sugarcane and non-sugarcane areas of KZN were sampled bi-monthly for white grub larvae, pupae and adults. An additional site that had been planted to sugarcane was surveyed as a control.
From 2012/13 Uromycladium acaciae (wattle rust) has spread throughout the Acacia mearnsii (black wattle) growing areas of South Africa. The newly emerged disease affects trees of all age classes and causes growth reductions and mortalities with severe infestations. Fungicides have been tested and found to be effective for managing the disease, with the timing of application necessary for optimal control.
Acacia mearnsii (black wattle) plantations in South Africa cover approximately 110 000 ha. Uromycladium acacia (wattle rust) has spread over Limpopo to the Western Cape of South Africa. This disease of black wattle causes reductions in growth and mortalities in severe infections. In October 2014 six trials were initiated in Mpumalanga and KwaZulu-Natal to determine the effectiveness of fungicides, varied application schedules, and adjuvants for the management of wattle rust.
White grubs can contribute to serious transplant mortality immediately following re-establishment. Registered insecticide treatments of deltamethrin and imidacloprid have been deemed highly hazardous and their use is restricted by the Forest Stewardship Council (FSC). Therefore, there is an immediate need to find effective alternative products for the control of white grubs. A previous pot trial was conducted to screen a broad range of alternative chemical and biological products for the control of white grubs.
Soil compaction poses a threat to the productivity of South African commercial eucalypt plantations. The impact of compaction on dolerite- and aeolian- derived soils is well understood; however, there is no available information for sandstone-derived soils. In addition, the impact of leaving harvest residues or ripping these soils to reduce the degree of compaction is not fully understood.
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.