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.
Robust management decision-making requires constant improvements to the understanding of the short- and longer-term impacts of re-establishment practices on tree performance. There is a lack of information regarding the impact of fertilisation and vegetation management on the longer-term (mature stand or rotation-end) yield of pines grown for pulpwood in South Africa.
Two trials were implemented in the KwaZulu-Natal Midlands in October 2016 (at Ingwe and Balgowan plantations), to test the efficacy of eight different insecticides (synthetic and organic) for the management of foliar insect pests. The Ingwe trial was planted with Eucalyptus dunnii and the Balgowan trial was planted with Eucalyptus badjensis.
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.