Survey of psylloids (Hemiptera: Psylloidea) in citrus environments in the Afrotropical region of South Africa

Psylloids (Hemiptera: Psylloidea) are sap-sucking insects, some of which are major agricultural pests vectoring plant-pathogens. In order to safeguard the southern African citrus industry, due to the presence of the invasive Diaphorina citri Kuwayama 1908 (Psyllidae) in East and West Africa, early detection surveys for the pest in citrus production regions are required. This study catalogued and assessed the community structure of indigenous psylloids species in commercial citrus. Psylloids were collected using yellow sticky traps and insect sweep-net. A total of 4,900 psylloids specimens were collected, representing five families (Psyllidae, Triozidae, Aphalaridae, Liviidae, and Carsidaridae), 19 genera, and 47 species. Seventeen species were shared between the citrus orchards and adjacent natural vegetation; 28 were collected from the orchards using both collection methods [yellow sticky traps (orchards only) and insect sweep-net]. The abundance of psylloids using yellow sticky traps was 3-fold higher (3,265) than that of psylloids collected using a sweep-net (1,635). The most abundant species were Trioza erytreae, Acizzia sp. 3, Acizzia russellae-group, Cacopsylla sp. 1, Diaphorina punctulata, Diaphorina virgata, Euryconus sp. 1, Pauropsylla trichaeta, and Retroacizzia mopanei. Among these, only T. erytreae was found to utilise citrus as a host-plant. Overall, yellow sticky traps proved to be a more effective monitoring tool than sweep-netting, capturing higher numbers of psylloids in the orchards, and are thus recommended for early detection and ongoing surveillance of invasive psyllids of potential economic concern in citrus agroecosystems. However, it should be noted that yellow sticky traps were not deployed in the natural indigenous vegetation.