Factors influencing arthropod diversity in the citrus landscape in Tshipise, Limpopo Province South Africa

Abstract

Citrus plants play a crucial role in global food and nutrient supplies. South Africa exported 165.1 million cartons of citrus during the 2023 season and projected growth to 200 million cartons within four years. However, citrus crops are vulnerable to pest infestations, leading to a heavy reliance on chemical pesticides. Different pesticide types and dosages leave varying residue levels on treated citrus, with strict maximum residue limits (MRLs) enforced by global markets. Ongoing shifts in MRL standards and concerns over chemical dependence have pressured Southern African citrus producers to adopt Integrated Pest Management (IPM) approaches that balance effective pest control with minimised chemical use. This study investigated the factors influencing arthropod diversity in citrus agroecosystems, focusing on how landscape heterogeneity influences IPM. Using a landscape context approach, it quantified arthropod diversity within citrus orchards and surrounding habitats and edges to understand how these areas support beneficial arthropods like predators and parasitoids (Chapter 2). Results showed that diverse landscapes supported higher populations of beneficial arthropods in natural habitats, enhancing natural pest control, whereas croplands harboured more pest species. Additionally, the study evaluated the effects of excluding insectivorous vertebrates to assess their roles in pest suppression, crop damage reduction, and the spatial distribution of Thaumatotibia leucotreta (Chapter 3). By elucidating arthropod population dynamics, the role of landscape structure and context, and insectivorous vertebrates, this study highlights the importance of landscape heterogeneity in enhancing natural pest control within citrus agroecosystems. Findings show that maintaining diverse, non-crop habitats near croplands can support natural enemy populations, reducing reliance on chemical pesticides in IPM. The study also reveals that landscape context, especially proximity to natural habitats, influences the distribution and impact of crucial pests like T. leucotreta within citrus orchards. These insights offer practical guidance for optimising IPM approaches, suggesting that incorporating elements of natural habitats within agricultural landscapes can improve pest suppression and align with evolving global standards for pesticide residue limits.