A New Record of Mealybugs (Paracoccus burnerae Brain – Hemiptera: Pseudococcidae) and Leafhoppers (Mngenia angusta Theron – Cicadellidae: Coelidiinae) on a Southern African Medicinal Plant, Greyia radlkoferi

Cultivation of medicinal plants at a commercial scale brings with it challenges such as pests and diseases. In their natural habitat, medicinal plants may generally be less infested with pests and diseases, whereas they may be severely attacked in agro-ecosystems (Verma 2006). The feasibility of commercial cultivation of medicinal plants depends on their ability to thrive in monoculture to meet the required production volumes (Misra 2009). Medicinal plants contain secondary metabolites which are believed to be produced in defence of pathogen attack. Despite the secondary metabolites contained in medicinal plants, they are still prone to damage by pests and diseases, leading to reductions in crop productivity and quality (Gahukar 2012). With commercial cultivation of indigenous medicinal plants becoming a priority in the Biodiversity Economy Strategy of the South African Government, knowledge generation on pest and disease management, which begins with pest and disease identification, is of practical and economic significance. Insect pests hinder the supply of good quality products, transmit plant viruses and reduce crop productivity under monoculture. Greyia radlkoferi Szyszyl (family Melianthaceae) is an important medicinal plant species indigenous to South Africa and Swaziland (Nogemane & Prinsloo 2018). Extracts from the leaves of this species have been proven to have cosmeceutical properties (Lall et al. 2016), thus making it one of the commercially important species. The extracts are used against dermatological disorders associated with melanin, such as hyper-pigmentation and to overcome skin irritations (Lall et al. 2016; Nogemane & Prinsloo 2018). Realising the potential for cosmeceutical product development from G. radlkoferi demands that the species be produced on a commercial scale for a sustainable supply of the plant material (Nogemane & Prinsloo 2018). Production of good quality finished products depends, amongst others, on the quality of raw medicinal plant material supplied (Nogemane 2017). Wild harvested medicinal plants present challenges such as contamination with other unwanted materials, metabolite variation and/or adulteration. A challenge with the continuous supply of G. radlkoferi leaves is that the species is deciduous, as it sheds its leaves at low temperatures. Thus, there are attempts to grow the species under controlled environments to ensure a continuous and sustainable supply of the leaves. The objective of this study was to identify and document potential pests of Greyia radlkoferi cultivated in a controlled environment. Greyia radlkoferi plants grown in a glasshouse were monitored for pest infestation in the 2018 and 2019 growing seasons. The plants were grown in a medium composed of sand and compost bark (1:1 v/v). Moisture loss was monitored daily and the plants were watered three times a week. The plants were regularly scouted during the growing seasons for the presence of any pests and their related damage. In the 2019 season, insect damage was observed on the leaves of the plants. The symptoms included white cottony masses on the leaves, yellow to brown spots on the leaves and leaf wilting. The symptoms were observed on 80 % of the plants. The observed insect pests causing damage were carefully collected in Petri dishes. The samples were labelled and sent to the Agricultural Research Council–Plant Health and Protection (ARC-PHP) for identification using gross morphological traits, after which they were assigned with accession numbers and deposited in the National