Invasive Alien Plants in Sub-Saharan Africa: A Review and Synthesis of Their Insecticidal Activities

Abstract

Despite the cornucopia of agricultural, economic and ecological ramifications of invasive alien plant species (IAPs) in sub-Saharan Africa, studies on their potential use as bio-insecticides have not received adequate attention compared to the burgeoning plethora of literature on their use in ethnomedicine. In the current study, we review the existing, but scattered literature on the insecticidal activity of different parts of some IAPs; specifically those invasive in sub-Saharan Africa but with published literature from Africa and elsewhere. From our literature survey, we found that 69 studies from four continents (Africa, Asia, North America and South America) reported the insecticidal activity of 23 plant species from 13 families (Asteraceae = 6 species; Solanaceae = 3 species; Apocynacee, Fabaceae and Euphorbiaceae 2 species each; Araceae, Bignoniaceae, Chenopodiaceae, Meliaceae, Mimosaceae, Myrtaceae, Papaveraceae, and Verbenaceae = 1 species each) that are invasive in, and alien to Africa. The highest number of published case studies were from India (n = 19) and Nigeria (n = 15). We found that varying concentrations of extracts or powders from different plant parts caused 50–100% mortality against a myriad of insect pests of agriculture and environmental importance. Our review discussed the prospects for exploiting IAPs as pesticidal plants in African countries especially among resource-poor small-holder farmers and locals to improve agricultural productivity and livelihoods. Finally, we highlighted safety concerns and challenges of using IAPs as bio-insecticides in Africa and formulates appropriate recommendations for future research.

An Invasive Plant Parthenium hysterophorus Reduces Native Forage Cover

“…Their invasion and dominance in new geographic regions induces serious social and ecological impacts (Ojija & Ngimba, 2021;Prass et al, 2022). For instance, they threaten human well-being, biodiversity, pollination, and ecosystem functioning and services (Laizer et al, 2021;Ojija, 2022;Uyi et al, 2021). IAPs have been referred to as ecosystem engineers because of the alterations they bring about in the recipient environments (Perkins et al, 2011).…”

Review of Invasive Plant Functional Traits and Management Using Remote Sensing in Sub-Saharan Africa

“…There are many IAPs that have been reported in SSA countries [6,[70][71][72]. Table 2 provides examples of detrimental IAPs found in SSA.…”

“…Table 2 provides examples of detrimental IAPs found in SSA. They are widely distributed throughout the region and have a major impact on the natural environment, biodiversity, and livelihoods [70,72,73]. Numerous IAPs emit secondary compounds, or allelopathic chemicals, which can change the soil chemistry or physicochemical characteristics, including microbial populations, soil organic matter content, and the availability of nutrients [74][75][76][77].…”

“…Thus, because of the IAPs' negative effects on agricultural production [71], biodiversity conservation, human health [70,78], and other socioeconomic development activities in SSA [16,36,77,80], the UN SDGs are in peril. Subject to socioeconomic factors, anthropogenic activities, and climate change [81], IAP invasions are likely to increase further in the future, mainly in arable and urban environments in SSA [72,76]. Therefore, in order to effectively manage IAPs, strategic management plans combining their functional traits and RS should be taken into account.…”

“…The UN SDGs and human livelihoods-such as farming and livestock rearing-are supported by healthy, uninvaded ecosystems because they offer ecosystem services such as controlling water flow, foraging, recycling nutrients, producing food-such as seeds, fruits, and vegetables-controlling climate change, and biodiversity conservation [82,83]. However, the invasions of IAPs on pristine ecosystems in SSA could result in the loss of biodiversity and valuable ecosystem services [2,80] with a deleterious impact on human livelihoods (decreases in or losses of crop yields or livestock productivity) and eventually failure to meet the SDGs [72]. In SSA, biological invasions caused by IAPs have proven to be a significant problem toward achieving the UN SDGs [16,36,83].…”