Abstract
Simple SummaryThe past decade has seen Africa being invaded by an invasive and destructive insect pest of tomato, the South American tomato pinworm. To date, the pest insect has since spread to almost the entire continent at lightning speed. Farmers have responded to this pest pressure through the sole injudicious use of chemical pesticides. However, this method of control is expensive, not effective (owing to reported insecticide resistance) and has potential adverse effects on the environment (including humans). To mitigate this, more environmentally friendly, bio-based and sustainable alternatives need to be put in place. Natural substances (NSs), for example, the use of pesticidal plant extracts, naturally occurring antagonists and related substances, can be used in this regard. A literature review was conducted explaining various factors that contributed to successful invasion by the pinworm. The review also explored various control mechanisms (e.g., biological control agents) that can be used in combination with natural and other low risk substances in a holistic way for successful pest control. Focus was also taken on the enabling and limiting factors that influence farmers in embracing the use of these NSs in an integrated approach.The South American tomato pinworm Tuta absoluta (Meyrick) has aggressively invaded the African continent. Since its first detection in North Africa in Morocco and Tunisia in 2008, it has successfully invaded the entire southern, eastern and western Africa, where it has been on the offensive, causing significant damage to Solanaceous food crops. While control of this prolific invader is primarily based on conventional synthetic pesticides, this form of control is consistently losing societal approval owing to (1) pesticide resistance development and consequential loss of field efficacy; (2) growing public health concerns; (3) environmental contamination and loss of biological diversity and its associated ecological services; and (4) unsustainable costs, particularly for resource-poor African farmers. As such, more ecologically sound pest management strategies, e.g., the use of natural substances (NSs), may offer a more sustainable approach to tackling this offensive. A systematic literature search through digital libraries and online databases (JSTOR, PubMed, Web of Science, SCOPUS and Google Scholar) was conducted using predetermined keywords on T. absoluta, e.g., South American tomato pinworm. We use this to explain the invasion of T. absoluta in Africa, citing mechanisms facilitating African invasion and exploring the potential of its control using diverse biological control agents, natural and low-risk substances. Specifically, we explore how botanicals, entomopathogens, semiochemicals, predators, parasitoids, host plant resistance, sterile insect technique and others have been spatially employed to control T. absoluta and discuss the potential of these control agents in African landscapes using more integrated approaches. We discuss the use of NSs as assets to general insect pest control, some potential associated liabilities and explain the potential use and barriers to adoption in African systems from a legislative, economic, ecological and social standpoint.
Highlights
Invasive insect pests are widely recognised as major threats to agricultural production, biodiversity conservation and the maintenance of ecological integrity [1,2,3]
The continental invasion of T. absoluta represents a significant biosecurity threat that affects the majority of livelihoods dependant on agricultural sustenance
Insecticide use against T. absoluta has been the common default response to pest pressure
Summary
Invasive insect pests are widely recognised as major threats to agricultural production, biodiversity conservation and the maintenance of ecological integrity [1,2,3]. It is thought to have originated from the Andes region in Peru before spreading to Latin American countries during the 1960s [17,18] It is an endemic Neotropical insect pest whose initial distribution was restricted to its native range in South America, it has successfully extended its geographical range following an unintentional introduction in the Mediterranean basin [15,19,20]. Synthetic insecticides affect (i) non-target biological diversity and their related ecosystem services, e.g., natural enemies and pollinators, disrupting desirable trophic interactions; (ii) development of pest resurgence; (iii) insecticide resistance development; and (iv) public health, owing to residual insecticide contamination [3,49,50,51,52] Some of these vices have already been observed in T. absoluta chemical control, e.g., insecticide resistance [53,54] and non-target effects on beneficial fauna [55]. We discuss barriers to the adoption and use of NSs in African agricultural systems from a legislative, economic, ecological and social standpoint
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