Plants with pesticidal properties have been investigated for decades as alternatives to synthetics, but most progress has been shown in the laboratory. Consequently, research on pesticidal plants is failing to address gaps in our knowledge that constrain their uptake. Some of these gaps are their evaluation of their efficacy under field conditions, their economic viability and impact on beneficial organisms. Extracts made from four abundant weed species found in northern Tanzania, Tithonia diversifolia, Tephrosia vogelii, Vernonia amygdalina and Lippia javanica offered effective control of key pest species on common bean plants (Phaseolus vulgaris) that was comparable to the pyrethroid synthetic, Karate. The plant pesticide treatments had significantly lower effects on natural enemies (lady beetles and spiders). Plant pesticide treatments were more cost effective to use than the synthetic pesticide where the marginal rate of return for the synthetic was no different from the untreated control, around 4USD/ha, compared to a rate of return of around 5.50USD/ha for plant pesticide treatments. Chemical analysis confirmed the presence of known insecticidal compounds in water extracts of T. vogelii (the rotenoid deguelin) and T. diversifolia (the sesquiterpene lactone tagitinin A). Sesquiterpene lactones and the saponin vernonioside C were also identified in organic extracts of V. amygdalina but only the saponin was recorded in water extracts which are similar to those used in the field trial. Pesticidal plants were better able to facilitate ecosystem services whilst effectively managing pests. The labour costs of collecting and processing abundant plants near farm land were less than the cost of purchasing synthetic pesticides.

Sustainable methods to control insect pests that affect crop yield have become a great challenge to mainly smallholder farmers. Beneficial insects in agricultural fields play an important role in natural pest control and pollination. The use of synthetic and botanical pesticides has detrimental effects to both natural enemies and pollinators in agricultural fields. The pesticides affect the survival of a range of life cycle stages, reductions in reproductive capacity, changes in the suitability of hosts for parasitising or predation, reduced emergence of parasitoids from sprayed host eggs and cause direct mortality. This has caused a serious menace to biological control agents and pollinators. When natural enemies are reduced, even more serious consequences may result for pest population dynamics which include the phenomena of resurgence and eruption of secondary pests. The decrease in pollinators reduces agricultural productivity. This review aims at exploring the side effects of synthetic and botanical pesticides on beneficial insects to give the basis for research on the negative impacts of synthetic and botanical pesticides on these insects. This information will assist in optimizing the use of pesticides in integrated pest management programmes by employing more sustainable and ecosystem benign practices such as the use of right dosage and selective pesticides in agricultural fields.

Implementation of socially acceptable and environmentally desirable solutions to soil erosion challenges is often limited by (1) fundamental gaps between the evidence bases of different disciplines and (2) an implementation gap between science-based recommendations, policy makers and practitioners. We present an integrated, interdisciplinary approach to support co-design of land management policy tailored to the needs of specific communities and places in degraded pastoral land in the East African Rift System. In a northern Tanzanian case study site, hydrological and sedimentary evidence shows that, over the past two decades, severe drought and increased livestock have reduced grass cover, leading to surface crusting, loss of soil aggregate stability, and lower infiltration capacity. Infiltration excess overland flow has driven (a) sheet wash erosion, (b) incision along convergence pathways and livestock tracks, and (c) gully development, leading to increased hydrological connectivity. Stakeholder interviews in associated sedenterising Maasai communities identified significant barriers to adoption of soil conservation measures, despite local awareness of problems. Barriers were rooted in specific pathways of vulnerability, such as a strong cattle-based cultural identity, weak governance structures, and a lack of resources and motivation for community action to protect shared land. At the same time, opportunities for overcoming such barriers exist, through openness to change and appetite for education and participatory decision-making. Guided by specialist knowledge from natural and social sciences, we used a participatory approach that enabled practitioners to start co-designing potential solutions, increasing their sense of efficacy and willingness to change practice. This approach, tested in East Africa, provides a valuable conceptual model around which other soil erosion challenges in the Global South might be addressed.

Plants with pesticidal properties have been investigated for decades as alternatives to synthetics, but only a handful have been commercialised and developed as non-food cash crops. One of the reasons why pesticidal plants are failing to deliver new pesticidal products is that they are often not evaluated under field conditions by farmers. Furthermore, many aspects of pesticide use related to environmental safety, such as their impact on beneficial organisms, remain under-evaluated. With a view to overcoming these bottlenecks, extracts made from six abundant weed species found across sub-Saharan Africa (Bidens pilosa, Lantana camara, Lippia javanica, Tithonia diversifolia, Tephrosia vogelii and Vernonia amygdalina) were evaluated in on-station and on-farm trials over two years (2015 and 2016) in two different countries (Tanzania and Malawi) on common bean plants (Phaseolus vulgaris). All plant species offered effective control of key pest species that was comparable in terms of harvested bean yield to a synthetic pyrethroid. Furthermore, the plant pesticide treatments had significantly lower negative effects on natural enemies (hover flies, lacewings, ladybird beetles and spiders). Thus, pesticidal plants were better able to support ecosystem services whilst effectively managing pests. Small holder farmer rankings on the perceived efficacy of the different plant species indicated that T. vogelii was the most preferred and effective, achieving bean yields as good as the synthetic, if not better. As T. vogelii is fast growing with a well-known and understood phytochemistry, it is an excellent candidate for commercial development to supplement pyrethrum production by African small holder farmers.

Increased soil erosion is one of the main drivers of land degradation in East Africa's agricultural and pastoral landscapes. This wicked problem is rooted in historic disruptions to co-adapted agro-pastoral systems. Introduction of agricultural growth policies by centralised governance resulted in temporal and spatial scale mismatches with the complex and dynamic East African environment, which subsequently contributed to soil exhaustion, declining fertility and increased soil erosion. Coercive policies of land use, privatisation, sedentarisation, exclusion and marginalisation led to a gradual erosion of the indigenous social and economic structures. Combined with the inability of the new nation-states to provide many of the services necessary for (re)developing the social and economic domains, many communities are lacking key components enabling sustainable adaptation to changing internal and external shocks and pressures. Exemplary is the absence of growth in agricultural productivity and livelihood options outside of agriculture, which prohibits the absorption of an increasing population and pushes communities towards overexploitation of natural resources. This further increases social and economic pressures on ecosystems, locking agro-pastoral systems in a downward spiral of degradation. For the development and implementation of sustainable land management plans to be sustainable, authorities need to take the complex drivers of increased soil erosion into consideration. Examples from sustainable intensification responses to the demands of population increase, demonstrate that the integrity of locally adapted systems needs to be protected, but not isolated, from external pressures. Communities have to increase productivity and diversify their economy by building upon, not abandoning, existing linkages between the social, economic and natural domains. Locally adapted management practices need to be integrated in regional, national and supra-national institutions. A nested political and economic framework, wherein local communities are able to access agricultural technologies and state services, is a key prerequisite towards regional development of sustainable agro-pastoral systems that safeguard soil health, food and livelihood security.