Browsing by Author "Vanek, Steven"

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Farmers’ insights and practices on sustainable soil nutrient and pest management in semi-arid Eastern Africa
(MDPI, 2025-03-12) Ojuu, David; Mkindi, Angela; Meya, Akida; Giliba, Richard; Vanek, Steven; Belmain, Steven
The need to increase agricultural production for food, fiber, and feed for a growing population is a global call. Sub-Saharan Africa currently experiences declining soil fertility and increasing pest pressures affecting agricultural production. Soil fertility and pest management practices tend to vary greatly among smallholder farmers due to farm-based limitations, attitudes, and perceptions. Using focus group discussions and individual farmer interviews, we evaluated the socio-economic factors influencing the production and utilization of nutrient resources by smallholder farmers. We also assessed factors for pest prevalence and management by smallholder farmers. We observed that the major organic nutrient fertilizer resources used by farmers are farmyard manure and crop residue recycling. The production and utilization of organic nutrient fertilizer resources vary according to agroecological zone, influenced by livestock ownership, grazing management, and farmer organization; Farmer Research Network farmers show optimal use of nutrient resources compared to non-Farmer Research Network farmers. Pest problems varied across agroecologies and were influenced by field management gradients. We noted that FRN farmers used ecologically relevant pest management approaches more frequently than non-FRN farmers. Our findings on nutrient resources and pest management highlight context-specific issues to leverage to promote agroecological approaches for agricultural productivity and resilient semi-arid landscapes.
Pesticidal Plant Treatments Combined with Improved Soil Fertility Can Reduce Damage Caused by Fusarium Wilt (Fusarium oxysporum f.sp. phaseoli) and Bean Fly (Ophiomyia phaseoli) in Common Bean Production (Phaseolus vulgaris L.)
(MDPI, 2024-06-06) Ngoya, Zuwena; Mkindi, Angela; Vanek, Steven; Stevenson, Philip; Ndakidemi, Patrick; Belmain, Steven
Common bean production is constrained by a multitude of biotic constraints including bean flies and Fusarium wilt in tropical and subtropical farming systems globally. As these pests and diseases attack the crop beneath the soil, excessive applications of synthetic pesticides are frequently used for their control. The use of plant-based pesticides could be a more sustainable management approach; however, few studies have investigated their application for controlling soil-borne pests and diseases. This study aimed to evaluate the efficacy of pesticidal plants and soil fertility management for controlling bean fly (Ophiomyia spp.) and Fusarium wilt (Fusarium spp.) using extracts and pastes of Azadirachta indica, Tephrosia vogelii, Tagetes minuta, Lippia javanica, Cymbopogon citratus and Ocimum gratissimum. To protect against Fusarium wilt and bean fly, pesticidal plants were applied as a seed coating and/or foliar spray, and demonstrated that common bean seeds coated with T. vogelii resulted in higher yields than other pesticidal plants and the synthetic pesticide control treatment. Treatments to target bean fly damage showed no significant difference between application methods on the oviposition rate of bean fly. An integrated treatment of T. minuta with 2 g Diammonium phosphate fertilizer and high compost led to higher yields than other treatments. Our results indicate that key soil-borne pests and pathogens of common bean can be effectively managed without synthetic pesticide inputs, while seed ball pastes of pesticidal plants combined with soil fertility management can increase crop yields using cost-beneficial agroecological farming systems.
Understanding farmer knowledge and site factors in relation to soil-borne pests and pathogens to support agroecological intensification of smallholder bean production systems
(Frontiers in Sustainable Food Systems, 2023-03-29) Ngoya, Zuwena; Mkindi, Angela; Vanek, Steven; Ndakidemi, Patrick; Stevenson, Philip; Belmain, Steven
Introduction: Pests and diseases limit common bean (Phaseolus vulgaris) production in intensifying smallholder farming systems of sub-Saharan Africa. Soil-borne pests and diseases (SPD) are particularly challenging for farmers to distinguish and manage in cropping systems that vary in terms of soils, farmer knowledge, and management factors. Few studies have examined soil drivers of SPD in smallholder systems, integrated with farmers' perceptions and management practices. Methods: In Kilimanjaro, Tanzania, we assessed farmer knowledge and SPD management for common bean alongside soil type and soil quality. Focus group discussions and field survey findings including farmer observations and soil nutrient balances were integrated with soil analyses of farmers' fields. Multiple correspondence analysis (MCA) and principal component analysis (PCA) assessed relationships among farmer demographics, pests and diseases, soil characteristics, and management practices. Results and discussion: Surveys revealed that 100% of farmers knew of the bean foliage beetle (Ootheca bennigseni) but few recognized the soilborne pest Ophiomyia spp. or bean fly despite it being more destructive. About a third of farmers knew of root rot diseases caused by Pythium spp. and Fusarium spp. Synthetic pesticides were used by 72% of farmers to control pests, while about half that (37%) used pesticidal plants, particularly Tephrosia vogelii extracts sprayed on foliage. Regarding SPD, 90% of farmers reported that their management practices were ineffective. Meanwhile, synthetic fertilizers were used by nearly all farmers in beans intercropped with maize (Zea mays), whilst very few farmers used manure or compost. Soil available phosphorus was lowbut showed a balance between inputs and outputs regardless of whether fields were owned. Field nitrogen balances were more negative when fields were owned by farmers. An MCA showed that older farmers employed a greater number of pest control practices. The PCA showed that field variability was dominated by soil organic matter, elevation, and soil pH. Higher organic matter levels were also associated with less stunting and wilting of beans observed by farmers. Our results suggest that research and farmer learning about SPD ecology are key gaps, alongside recycling of organic residues to soils. Cost-effective and sustainable practices to manage bean SPDs for smallholders are also needed.