Bioactivity of common pesticidal plants on fall armyworm larvae (spodoptera frugiperda)

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) is a recent invasive pest species that has successfully established across sub‐Saharan Africa where it continues to disrupt agriculture, particularly smallholder cereal production. Management of FAW in its native range in the Americas has led to the development of resistance to many commercial pesticides before its arrival in Africa. Pesticide use may therefore be ineffective for FAW control in Africa, so new and more sustainable approaches to pest management are required that can help reduce the impact of this exotic pest. Pesticidal plants provide an effective and established approach to pest management in African smallholder farming and recent research has shown that their use can be cost‐beneficial and sustainable. In order to optimize the use of botanical extracts for FAW control, we initially screened ten commonly used plant species. In laboratory trials, contact toxicity and feeding bioassays showed differential effects. Some plant species had little to no effect when compared to untreated controls; thus, only the five most promising plant species were selected for more detailed study. In contact toxicity tests, the highest larval mortality was obtained from Nicotiana tabacum (66%) and Lippia javanica (66%). Similarly, in a feeding bioassay L. javanica (62%) and N. tabacum (60%) exhibited high larval mortality at the highest concentration evaluated (10% w/v). Feeding deterrence was evaluated using glass‐fibre discs treated with plant extracts, which showed that Cymbopogon citratus (36%) and Azadirachta indica (20%) were the most potent feeding deterrents among the pesticidal plants evaluated. In a screenhouse experiment where living maize plants infested with fall armyworm larvae were treated with plant extracts, N. tabacum and L. javanica were the most potent species at reducing foliar damage compared to the untreated control whilst the synthetic pesticide chlorpyrifos was the most effective in reducing fall armyworm foliar damage. Further field trial evaluation is recommended, particularly involving smallholder maize fields to assess effectiveness across a range of contexts

Agroecological management of fall armyworm using soil and botanical treatments reduces crop damage and increases maize yield

IntroductionFall armyworm continues to disrupt smallholder farming systems across sub-Saharan Africa, with sporadic outbreaks and chronic cereal crop losses. Smallholders have been adapting to the pest by increasing crop surveillance for targeted control measures and developing low-cost solutions. For example, some report placing soil or ash in maize whorls where the mechanism of pest control may be suffocation, abrasion leading to desiccation, or through the introduction of soil-borne entomopathogens.MethodsTo verify the efficacy of this approach we evaluated different soil types on maize infested with fall armyworm to assess their efficacy. We also evaluated the efficacy of pesticidal plant species, powdered and placed in leaf whorls to control fall armyworm. Results and discussionDifferent United States Department of Agriculture-characterised soil types (sand, loam, clay) and wood ash were effective in reducing the number of larvae and maize leaf damage by approximately 50%. Maize yield with the synthetic control (chlorpyriphos) was 13,700 kg/ha, which was 42% higher than the untreated control (7,900 kg/ha). Soil and ash treatments yields between 10,400 to 12,400 kg/ha were 24-36% higher than the untreated control. Dry soil applied after watering was most effective regardless of soil type. However, wet soil treatments applied before watering were also highly effective in reducing the number of fall armyworm larvae and reducing insect damage to maize leaves. Botanical powders from Azadirachta indica, Nicotiana tabacum, Cymbopogon citratus and Lippia javanica were also effective when applied to maize leaf whorls. Plant powder treatments and water extracts were significantly effective in reducing the number of larvae and leaf damage. The highest yield obtained with botanicals was observed with A. indica powder (5,600 kg/ha), C. citratus extract (5,800 kg/ha) and N. tabacum extract (5,800 kg/ha), where the synthetic treatment yield was 6,900 kg/ha and the untreated yield was 1,700 kg/ha. We conclude that smallholder farmer innovations in managing fall armyworm are effective low-cost options. Scientific validation of soil treatments and botanicals should help increase the confidence of policy makers and allow knowledge extension services to recommend their use to smallholder farmers, which in turn may reduce reliance on imported synthetic pesticides and improve farmer resilience, circular economies and human and environmental health

Rolling out of agro-ecology practices in Lukudzi Section, Ntcheu, Malawi: A case study

This bulletin has been prepared by the Malawi Agro-Ecological Intensification (AEI) hub as a case study to highlight how AEI practices are being rolled out in Chibale Model Village, Likudzi Section, Manjawila Extension planning Area (EPA) in Ntcheu district. The efforts are led by public extension service, using multi-model extension approach-es and multi-stakeholder collaboration to harness synergy. FAO (2018) suggested ten elements of agro-ecology as analytical tools to help in identifying important properties of agro-ecological systems and approaches and also relevant considerations in developing enabling environments for agro-ecology. The ten elements also serve as guide to policy makers, practitioners and stakeholders in planning, managing and evaluating agro-ecological transitions. Thus the same FAO’s (2018) ten elements have been used as basis for appraisal. The review shows that all ten elements are being promoted in the area, with variation in intensity and scale, and also some more directly and others more indi-rectly. We identified areas needing more emphasis as market linkages, and responsible local governance to enable protection of resources in the field such as plant material used as cover in CA systems and long duration crops such as pigeon peas and cassava, from uncontrolled fires and free ranging animals. Through farmer field schools farmers are generating evidence of the use of neem leaf powder as organic treatment for notorious fall army worm infestation in maize. This is commendable and is worth scaling out

Role of Responsible Governance in Enhancing Integrated Goat Keeping and Cropping Systems in Southern Malawi: Trade-offs and Synergies towards Agroecological Transitions and Transformation

This brief reflects on the cases of two villages in Lingoni section, Domasi EPA in Machinga district, combined with literature review and key informant interviews, to highlight the significant contribution of village-level responsible governance in enhancing agroecological intensification amongst small holders. The study reveals that through using village by-laws as tools, successful control of free grazing of livestock and uncontrolled fires has been prevented for many years, allowing local cropping systems to embrace long season crops such as cassava and pigeon peas, and winter cropping including multiple cropping with irrigation. The full range of resulting agroecological benefits are presented and discussed including the trade-offs from all sides of the systems

An Insight of Parasitic Weeds in Africa and Scientific Developments: A Review

Parasitic weeds are a major threat to food security in Africa and control measures mostly done by smallholder farmers are not effective in eradicating the parasites. This results in a yield loss up to 100%. Parasitic weeds comprise Alectra vogelii, Striga spp., Orobanche spp., Rafflesia spp., and Phoradendron spp. Parasitic attachment is successful when three necessary conditions have been fulfilled namely the compatible host, suitable environment, and parasitic weed. These species parasite plant species through special attachment features such as modified leaves, suckers, haustoria, or modified roots. In Africa, the variability of parasitic weeds is largely driven by environmental factors such as temperature, rainfall, soil type, and crop husbandry practices. Warmer temperatures create more hospitable conditions for certain parasitic weeds, and allowing them to spread to new areas. Parasitic weed control is vital for effective crop production and the control strategies can be achieved through integrated weed control method that embraces mechanical, cultural, chemical, and biological methods. However, the most effective and crucial method is the cultivation of resistant varieties that provide long-term protection against parasitic weeds. Studies have been done on host-parasite attachment where dodder can send out new roots to infected neighbouring plants and spread their parasitic behaviour. More insight and knowledge should offer new goals for control within the life cycle of the parasitic weeds and their metabolic activities. Lastly, disciplines such as agronomy, plant breeding, nutrition, economics, and IT should play their roles effectively in combating parasitic weeds

Understanding variability in crop response to fertilizer and amendments in sub-Saharan Africa

Improved understanding of soil fertility factors limiting crop productivity is important to develop appropriate soil and nutrient management recommendations in sub-Saharan Africa. Diagnostic trials were implemented in Kenya, Malawi, Mali, Nigeria and Tanzania, as part of the African Soils Information Service (AfSIS) project, to identify soil fertility constraints to crop production across various cropping systems and soil fertility conditions. In each country, one to three sites of 10 km _ 10 km were included with each site having 12–31 field trials. The treatments tested included a control, an NPK treatment, three treatments in which the N, P and K nutrients were omitted one at a time from the NPK treatment, and three treatments in which secondary and micronutrients (Ca, Mg, S, Zn and B) simply referred here as multi-nutrients, manure and lime were added to the NPK. The field trials were conducted for 1–2 seasons; the test crop was maize except in Mali where sorghum was used. Nitrogen was limiting in all sites and generally the most limiting nutrient except in Sidindi (Kenya) and Kontela (Mali) where P was the most limiting. The general pattern in Kiberashi (Tanzania) shows none of the nutrients were limiting. K is mainly limiting in only one site (Mbinga) although incidences of K limitation were seen in almost all sites. Addition of multi-nutrients and manure further improved the yields of NPK in most sites. Cluster analyses revealed that maize crop in 11% of fields were highly responsive to nitrogen application, 25% (i.e., 21% poor and 4% fertile) ‘non-responsive’ to any nutrient or soil amendment, 28% being ‘low responsive’ and 36% of ‘intermediate response’. This study indicates that constraints to crop production vary considerably even within a site, and that addressing limitations in secondary and micronutrients, and increasing soil carbon can improve response to fertilizers. For sustainable crop production intensification in smallholder farming systems in SSA, there is need to develop management strategies to improve efficiency of fertilizer use and of other inputs, recognizing the site-specific nutrient response patterns at various spatial scales