Abstract
The Brown locust, Locustana pardalina (Walker, 1870) (Orthoptera: Acrididae), is a national pest in South Africa and poses a threat to rural and farming communities, as well as the country's food security, through damage to crops and competing with livestock for grazing and browsing resources. The lifecycle, behaviour, feeding preferences, and predators of the locust were reviewed in this study to assess the expected influence of weather variables on the success of the locust through outbreak years. Maps indicating the distribution of the Brown locust were created in QGIS with proxy location data and the weather variables (rainfall, maximum daily temperature and minimum daily temperature) were combined into graphs to show a visual representation of the relationship between the occurrence of the locusts and the weather. Through statistical analysis done in Microsoft Excel and IBM SPSS, it was found that temperatures have a statistically significant relationship with the occurrence of the locusts which was unexpected. Geographic modelling systems and maximum entropy niche modelling were used to produce models for current occurrence and predictions of future shifts in the distribution range of the Brown locust. Although it was expected that the locusts would experience an overall increase in distribution, the models showed a contraction of distribution area, which shifted southwards towards the coast and eastwards due to the expected desertification of the Karoo and rainfall continuing to occur along the South African coast and eastern parts of the country. From the factors considered, it can be concluded that climate change will influence the future distribution of the Brown locust that will exacerbate the ecological impact of climate change. This shift in distribution and expected increase of locust outbreaks due to climate change, may pose a problem for the already struggling local pest control organisations. The locusts are presently controlled chemically which has ecological and financial implications. As such alternatives to chemical control are discussed and the use of physical traps are proposed.