Department of Agricultural Economics

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Browsing Department of Agricultural Economics by Subject "Aerial spraying and dusting in agriculture"

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    A cost comparison of aerial and ground based approaches for the control of alien invasive pines in the Western Cape
    (Stellenbosch : Stellenbosch University, 2021-12) Boast, Kyle; Kleynhans, T. E.; De Lange, Willem (Senior economist); Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Agricultural Economics.
    ENGLISH SUMMARY : The rugged mountainous areas of the Western Cape fynbos are highly biodiverse, however alien invasive Pines remain a continual threat both in terms of its biodiversity and water supply as they are continually spreading and thriving uncontrollably. Felling has been the main clearing method; however, it has become too expensive and slow to use within these areas in comparison with the speed of the invasion. These environments are complex in that they can vary from site to site in terms of tree density, slope, surrounding obstructive vegetation and remoteness. These site properties often result in longer walk, removal and site access times which can significantly increase overall costs of labour-intensive methods such as felling. The problem is continuing to get worse over time and demands an investigation into alternative clearing methods. Chemical methods such as the Drill and Fill and Aerial Basal Bark Application (ABBA) method have increased the efficiency and scope of alien invasive Pine removal in other countries which have however not been tested for local conditions. The aim of this study was to determine under what site conditions these chemical control methods and the use of helicopters would be more cost effective compared to traditional felling which would encourage an integrated approach to managing the species. The study thus consisted of two novel clearing methods: the Drill and Fill method, the Aerial Basal Bark Application (ABBA) method and traditional felling currently used in practice. A work rate matrix was constructed which compared the financial implications of each clearing method at the various physical site combinations: tree density, slope, surrounding obstructive vegetation and remoteness. Expert knowledge was employed to validate the work rate and costing data. The study found that the higher productivity of the drill and fill teams outweighs their total daily team rate compared to traditional felling. The productivity of traditional felling was prevented by the mandatory higher safety and supervision requirements associated with chainsaw operation which resulted in the inclusion of unproductive team members, in contrast with all members of a drill and fill team using a drill from the added safety of drill operation. The relative lower weight of drill and fill equipment decreases walk times and increases productive working time. Consequently, most scenarios showed the drill and fill method is more cost-effective compared to traditional felling. The ABBA method is the preferred method at sites where isolated Pines are situated in dense fynbos with difficult access at slope gradients of 45° and higher. At these site combinations, ground teams experience longer walk times which reduces their productivity to such an extent that ABBA is comparatively more cost-effective. Additionally, at slope gradients of 45° and higher, high-altitude teams require specialized equipment which results in further reductions in their productivity. Helicopters should therefore target the species in their isolated spread stages before they reach reproductive maturity and spread large amounts of wind-blown seeds over considerable distances. The study assumed the helicopter had a high level of hours available per annum. In practice however this may not be the case due to unfavourable weather conditions in these mountainous areas which makes it risky for operators. Government must make use of a private contractor involved in agricultural crop spraying to prevent this from happening, as operations can be diverted to crop spraying in low lying areas when weather restricts invader tree eradication. This would allow the helicopter to work at a lower hourly rate than a government owned helicopter standing idle.