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.
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.
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.
Soil preparation prior to planting is no longer a purely manual operation, with semi-mechanised and fully mechanized pitting techniques becoming more frequently utilised. Manual pitting is well understood in South Africa; however, there is limited information on the impact of semi-mechanised or mechanised pitting techniques on tree performance. In addition, the impact of fertiliser application and placement in pits created by semi-mechanised and mechanised pitting is not fully understood.
South African pine growing areas, the plantations are managed under various silviculture treatments to produce numerous products. The diversity in stocking, rotation age, species, thinning regimes etc. creates a mosaic pattern. Within this mosaic pattern there is a need to establish trap trees to monitor the presence of Sirex noctilio.
Personnel involved in the initial Eastern Cape and KZN Sirex noctilio outbreak from 2005 to 2008 were also involved in releasing and monitoring levels of parasitism brought about by both parasitoids through Mpumalanga and Limpopo. The experience they gained and parameters which became key in managing the pest, would be beneficial to other Pine growers who had not experienced similar losses through high tree mortality due to S. noctilio.
In South African forest plantations, the soil pest complex can contribute to serious transplant mortality immediately following re-establishment. White grubs (Scarabaeidae larvae) are one of the most important components of the soil pest complex. The control of white grubs using insecticides is highly regulated by the Forest Stewardship Council (FSC), which promotes the production of wood in an environmentally sustainable manner. An effective control measure for soil-borne pests is deltamethrin, a chemical banned by the FSC but used by the forestry industry under temporary derogation.
Bark stripping of pine trees by baboons (Papio ursinus) is challenging the sustainability of the forestry industry in the Mpumalanga province of South Africa. To date, the drivers of this behavior are not clear and likely to be related to a combination of environmental factors and troop-specific acquired behavior. Understanding the extent of the damage and monitoring changes over time are key components of an effective management strategy.