Abstract
Banana pests (corm weevil and root nematodes) and diseases (Xanthomonas wilt of banana, banana bunchy top disease and fusarium wilt) are major constraints to banana production in Central Africa. The pests cause various degrees of yield reduction, while plants affected by three of the diseases eventually die before producing an edible bunch. Studies on yield gaps for most of these constraints are currently limited. This paper reviews yield gap studies of some root, tuber and banana crops broadly and with a specific focus on biotic constraints. It also presents an initial case study conducted in Burundi to understand yield gaps due to various banana pests and diseases. Bunch weights of banana varied widely at production zones in western Burundi due to biotic constraints. Boundary line analysis revealed large yield gaps due to the various pests. The often sub-optimal, medium and small bunch sizes found in visibly healthy fields however indicate that in addition to mitigating effects of biotic constraints, significant improvements in bunch weights could be attained through the application of agronomic/field management practices that enhance soil fertility, soil moisture content and soil health. Simple and robust methods [such as the boundary line analysis] for estimating yield gaps caused by pests and diseases, and abiotic constraints on farm are crucial for informing/guiding on the need to apply agronomic and/or disease control efforts. In addition, continuous/sustained field monitoring, with the involvement of farmers, over time will be necessary for a more accurate assessment of yield gaps caused by diseases and pests. Key words: Banana bunchy top disease, boundary line analysis, fusarium wilt, nematodes, weevils, Xanthomonas wilt.
Highlights
The boundary line analysis procedures and concepts described by Fremont et al (2009) and Wairegi et al (2010) and as described in the sections above were used with a slight modification as described in the steps as follows: (i) The most influential yield outliers were identified and dropped with the help of boxplots. (ii) Pearson correlation analysis was used to identify the relationship between the bunch weight and the biophysical constraints for the different banana cultivars
Large numbers of plants affected by Xanthomonas wilt of banana (XW) had been removed in the years, months and weeks prior to the survey
Percentage XW plant incidence as measured during the surveys does not reflect the overall severe damage done over time by this pathogen
Summary
The Great Lakes region of east and central Africa, of which Burundi is part, is endowed with a broad. Diversity of banana cultivars spread across a wide range of altitudes and agro-ecological zones. This region constitutes one of the secondary centers of Musa diversity, for the East African highland bananas, AAA-EAH (Karamura et al, 2004). Banana and plantain (Musa sp.) are an important staple and incomegenerating crop for rural communities in this region
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