Stump management in ex-eucalypt stands Eucalyptus trees planted commercially in forest plantations of South Africa have, in the cambium, lignotubers and epicormic buds that allow them to produce coppice shoots following the removal of the main stem. This coppice regrowth Noxolo Ndlovu | Forestry Research Scientist can be a source of competition for the next crop, which can lead to reduced and variable tree growth. As such, for the successful establishment and optimum productivity of the next crop or stand, coppice regrowth needs to be effectively controlled. Different methods to control stumps There are various methods that can be implemented to control coppice regrowth in ex-Eucalyptus stands. These include: Manual Removal This entails the manual removal of coppice using a sharp tool such as an axe or bush knife. Spraying Coppice Foliage With Herbicides Spraying coppice leaves, often with glyphosate, requires careful application to avoid damaging planted seedlings. Raising the nozzles to reach taller coppice increases the risk of spray drift and seedling damage. Basal Frill Treatment Herbicide, usually triclopyr based, is applied directly into cuts made at the base of the tree or stump. This method limits soil runoff and is best carried out before felling to avoid interference from harvest residues. Cut-Surface Treatment The application of herbicide, usually a triclopyr-based herbicide, to the cambium of the recently felled tree/cut stump. 01 03 04 02 Research shows that all the methods listed can be effective in controlling coppice regrowth. The herbicide Turbodor 29 MPA as a solution to challenges associated with cut-surface treatment operations In addition, when implemented correctly and at the appropriate time, no significant differences in tree performance (survival, growth and uniformity) have been observed between the different treatments at rotationend. In other words, there is no treatment that is necessarily superior to the others in terms of the resulting performance of the next crop at rotation-end. As such, the most suitable method is influenced by costs and other considerations, such as safety and the need to reduce reliance on herbicide use. In terms of costs, a Turbodor provides a potential solution to challenges associated with conventional cutsurface treatments, particularly the requirement for herbicides to be applied shortly after felling. Turbodor, a triclopyr-based herbicide, allows application up to six weeks post-felling. This can improve worker safety, as felling and timber extraction are likely to have been completed by this time. study published in 2017 showed that the cutsurface treatment was the most cost-effective treatment (R1 973.80 ha-1) compared to the basal frill treatment (R3 228.23 ha-1) and operations where the stump was not treated soon after harvesting, but a combination of coppice foliage spraying with glyphosate and manual removal of coppice was implemented from 14 weeks after planting (R2 650.50 ha-1) (Roberts et al. 2017). The lower cost of the cut-surface treatment was attributed to fewer labour units required (for example, 1.5 units ha-1) and lower quantities of herbicide used compared to the other methods. It is important to note, however, that the cost comparison by Roberts et al. (2017) was based on the same number of follow-up operations being implemented across the different treatments. The authors acknowledged that, in practice, the effectiveness of cutsurface and basal frill treatments in controlling coppice may reduce the need for follow-up operations. Therefore, the actual cost of these treatments may be lower than reflected in the study, particularly when compared with treatments relying on repeated foliage spraying and/or manual removal. So, if all the methods can work, and cut-surface treatment is relatively inexpensive, what is the problem? The problem is timing! Although cut-surface treatment has been documented as the most cost-effective method, the greatest limitation of this method, especially in the past, has been the fact that, for effective control, herbicides needed to be applied soon after felling, often within a day of felling. This presents challenges, as this is not always possible due to safety concerns in harvesting operations. EFFECTIVENESS OF THE VARIOUS METHODS A series of three trials conducted in subtropical, warm temperate and cool temperate forestry regions of South Africa showed that a single application of Turbodor at four, five or six weeks post-felling resulted in complete killing of treated Eucalyptus stumps (Figures 1 and 2). 24 25
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