Seasonal abundance and diversity of mites in Coffea arabica L. at Beaver Creek Coffee Estate, South Africa

A Dissertation Submitted in fulfillment of the requirements of the degree Master of Science In Plant Science In the Faculty of Science, at the University of the Witwatersrand, Johannesburg, South Africa 2023

The presence of multiple species of mites inside the leaf domatia of Coffea arabica is well documented by various studies. This study examined the influence of seasonal changes on the abundance and diversity of mites in the leaf domatia of Coffea arabica. The study furthermore documented the species of predatory mites that were associated with coffee. The results of the study showed that there was a significant variation in the abundance of mites due to changes in season. Mite counts were significantly higher in spring followed by autumn and lowest in summer. There was no correlation between the number of mites and temperature and relative humidity. Therefore, this study could not establish what drives the seasonal changes in the mite populations and we postulate that this was because we did not measure the microclimate of the individual trees we sampled. This would have given us more accurate data on the temperature and relative humidity experienced by these mites. The Shannon-Weiner Diversity Index was found to be highest in summer and lowest in winter. The Phytoseiidae, Tydeidae, Stigmaeidae, and Tenuipalpidae were found to be the predominant families in this study. This study is one of the few studies in South Africa to directly investigate the effects of seasonal changes in mite abundance, and could potentially open avenues for further research, particularly on what seasonal parameters drive the mite population changes. We recommend that future studies use Ibuttons to get a true measure of the climatic variables that are experienced by the mites sampled at a tree level

MM2024