Understanding and managing bacterial wilt and late blight of potato in Ethiopia: Combining an innovation systems approach and a collective action perspective

Shiferaw Tafesse Gobena

Research output: Thesisinternal PhD, WU


Potato production is on the rise in developing countries due to its considerable contribution to global food security. The livelihood of millions of smallholder farmers is dependent on this crop. However, various diseases such as bacterial wilt and late blight are primary constraints to potato production. Scholars have been devising different management methods to deal with these and other crop diseases. But the efficacy of most of the recommended integrated disease management methods is limited due to the specific context of smallholder farmers. Even though the importance of considering social and technical dimensions of crop disease management is recognised in the literature, there is a lack of knowledge on how the interplay between social and biophysical conditions aggravate or spread crop diseases. Particularly, information on the management of complex crop diseases that pose a collective risk to the interdependent smallholder farmers is limited. Effective management of crop diseases does not happen in isolation for the broader system, and it requires an improved understanding of the dynamics of social and biophysical conditions and identification of innovations that enhance the management of the diseases. The key aim of this thesis was to examine the social and biophysical factors that explain the widespread of bacterial wilt in potato in Ethiopia and investigate what technical and social innovations could help deal with the disease.

In Chapter 2, I identified various actors in the potato innovation system and studied how they understood the problem of bacterial wilt and late blight. The actors did not recognise the interdependency among themselves for effective management of the diseases. The extension system primarily followed a top-down technology transfer approach with limited achievement. Furthermore, only seed potato producers were targeted despite the socio-ecological interdependencies among seed and ware potato producers. Seed potato quality control approach was also problematic as there was no formal seed certification system in the country.

Guided by the findings in Chapter 2, Chapter 3 focused on understanding farmers’ knowledge and practices of bacterial wilt and late blight management. There was limited knowledge among farmers concerning the cause, spreading mechanisms, and management methods of the diseases. They did not recognise the causes of bacterial wilt and late blight as they did not link these diseases to living microorganisms that are contagious. Furthermore, farmers’ practices such as rogueing spread the disease further instead of controlling it as many farmers were uprooting and throwing away infected plants at the farm side. Crop rotation interval was also limited, and the majority of the farmers were practicing one season interval only.

Chapter 4 aimed at understanding how seed potato cooperatives monitor the occurrence and management of bacterial wilt. Seed potato cooperatives play a vital role in Ethiopian seed potato system. We developed a novel framework consisting of elements of a monitoring system for managing a complex disease like bacterial wilt in potato. The development of the framework was based on common-pool resource literature. The studied seed potato cooperatives had organised a self-monitoring system to address the problem of bacterial wilt. The cooperatives had committees which were responsible for enforcing sanctions on cooperative member farmers who did not adhere to the bylaws. The monitoring system's efficacy was questionable as the committees rarely rejected potato fields on the basis of disease occurrence or malpractices of the farmers. They also depended on visual observation to diagnose the disease, which failed to detect latent infection of the pathogen that causes bacterial wilt. Furthermore, many farmers did not trust the committees. The monitoring system did not address ware potato producers despite the interdependency among the farmers. The study indicated the importance of collective action among seed and ware potato producers. Hence, strengthening the capacity of seed potato cooperatives could enhance effective management of the disease by mitigating marketing infected seeds since the role of seed cooperatives will continue to be significant in the country’s seed system.

Chapter 5 adds to the understanding of the biophysical condition that has aggravated bacterial wilt incidence in the country—association between soil acidification and bacterial wilt as investigated. Most of the main potato growing districts were affected by soil acidity, and this, in turn, aggravated the incidence of bacterial wilt. Field experiments to test the effect of mitigating soil acidity using lime showed a significant reduction in bacterial wilt incidence. Furthermore, isolation and characterisation of Ralstonia solanacearum strains indicated Phylotype II. Thus, ameliorating soil acidity needs to be considered as a requirement to manage bacterial wilt under acidic soil conditions effectively. 

In Chapter 6, we conducted action research to investigate how seed and ware potato farmers learn to control bacterial wilt. The learning intervention was designed based on the findings in Chapters 2 and 3. Experiential learning and social learning approaches were found to be complementary in enhancing the capacity of smallholder farmers to deal with bacterial wilt. Farmers learned disease dynamics and how to deal with the problem collectively. They also identified the feasibility of various methods recommended to manage the disease in their context.

In Chapter 7, key social and biophysical factors that spread bacterial wilt were discussed. Social and technical interventions that could enhance the management of the disease were also discussed. In general, this thesis has shed light on social and biophysical conditions that spread bacterial wilt. This thesis argues that an integrated disease management approach is not sufficient to deal with complex diseases like bacterial wilt and late blight. Collective action among the interdependent smallholder farmers and coordination among the actors in the potato innovation system are needed.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
  • Struik, Paul, Promotor
  • van Mierlo, Barbara, Promotor
  • Lie, Rico, Co-promotor
  • Lemaga, B., Co-promotor, External person
Award date25 Aug 2020
Place of PublicationWageningen
Print ISBNs9789463954686
Publication statusPublished - 25 Aug 2020


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