Enhancement of plant extracts use for pest control and growth promotion of common bean (Phaseolus vulgaris)
For smallholder farmers, suitable plants for pest management and as foliar feed are obtained with ease, and when successfully exploited, could contribute to local income generation through commercialization. However, with extensive research on their efficacy, toxicity and availability, the use of plant extracts is not widely adopted especially for smallholder farmers in rural settings. This study focused on evaluating factors that can foster extensive use of plant extracts among smallholder farmers. Questionnaires and focus group discussion were used to assess the perception of farmers towards using pesticidal plants, highlighting possible challenges, benefits and future enabling aspects for sustainable bean crop production. Plots of 5m 2 were established by farmers where an evaluation of the efficacy of Tephrosia vogelii, Tithonia diversifolia and Lantana camara was done to ascertain their potential for common bean insect pest management and impacts on beneficial arthropods. Additionally, the study evaluated spatio-temporal variability in bioactive phytochemicals of the most effective plant (T. vogelii), as well as the contribution of T. vogelii and T. diversifolia towards growth promotion and yield of common beans. Results showed that high per cent (99%, n=67) of smallholder farmers had pest challenge and that only (39.7%, n= 27) reported using plant extracts. Likewise, farmers reported a lack of working tools and motivation from researchers and extension officers as a challenge hindering the use of plant extracts. Plant extracts showed efficacy in pest management compared with untreated control whereby T. vogelii significantly reduced abundance of aphids (0.06 ± 0.02) and foliage beetles (0.17±0.03 compared with untreated (0.4 ± 0.05 and 0.5 ± 0.04 respectively). Again, the increased grain yield was recorded on plots treated with T. vogelii (3.8 ± 0.23) and T. diversifolia (3.3 ± 0.23) compared with untreated beans (1.5 ± 0.16), when applied as a foliar spray (2.7 ± 0.20) compared with soil drench (2.1 ± 0.16). Phytochemical variation was noted in T. vogelii where an additional chemotype 3 was first recorded. Hence, under smallholder farming conditions, plant extracts can contribute to sustainable bean crop production if practical implementation that involves smallholder farmers is a priority.
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