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Powdery scab is a nasty seed-borne, soil-borne and even, through contaminated dust, air-borne potato disease. The culprit is Spongospora subterranea f. sp. subterranea (abbreviated as SSS), an obligate, parasitic plasmodiophorid with a wide host range. This parasite affects root systems, but also tubers. Moreover, it is the vector of the potato mop-top virus. From the Andes, it spread to most potato growing regions, especially in temperate zones. Its polycyclic life cycle, with an asexual and a sexual phase, and its robust resting spores make it difficult to control.

Wheat, the most important food crop, can be stored for a much longer time than potato. It is ground and made into flour or pasta that can be turned into bread or a dish at any time. Potato is only storable for a limited period, so it floods the market at harvest. Major benefits of processing for growers include regulating the availability of markets and price through contracts, and the decrease in the number of consumers buying fresh tubers is compensated by processors buying raw material. Processors add value and employment and consumers are offered a wide array of affordable and convenient products. Large potato processing companies produce annual sustainability reports advocating measures for growers to spare the habitat, more efficient processes in factories, newer and healthier products and supporting communities. These are recorded and viewed in a theoretical triangulation from the angles of processors, and those trying to bend the rules. The industry, especially when expanding to new (developing) markets, faces political, economic, social, technological, environmental and legal (PESTEL) issues that fluctuate according to the presence of a raw material base, competition and buying power and culture of the consumers., Wheat, the most important food crop, can be stored for a much longer time than potato. It is ground and made into flour or pasta that can be turned into bread or a dish at any time. Potato is only storable for a limited period, so it floods the market at harvest. Major benefits of processing for growers include regulating the availability of markets and price through contracts, and the decrease in the number of consumers buying fresh tubers is compensated by processors buying raw material. Processors add value and employment and consumers are offered a wide array of affordable and convenient products. Large potato processing companies produce annual sustainability reports advocating measures for growers to spare the habitat, more efficient processes in factories, newer and healthier products and supporting communities. These are recorded and viewed in a theoretical triangulation from the angles of processors, and those trying to bend the rules. The industry, especially when expanding to new (developing) markets, faces political, economic, social, technological, environmental and legal (PESTEL) issues that fluctuate according to the presence of a raw material base, competition and buying power and culture of the consumers.

Potato has strong links between the actors as varieties bred by breeders, crop management of growers and site location of processors strongly influence the yield and quality of the finished products. Here, the actors (breeders, growers, processors, retailers and users) in the value chain are recognized, and their information and material flows identified. The influence of genotype, environment and crop management and the efficient use of resources during the production of raw material, tubers harvested for processing purposes, are delineated. It is shown that climate change affects performance and that consumers looking for quality and new products are hardly interested in the primary processes, nor are breeders and processors showing interest in consumer concerns. Crop performance is dependent on yield and quality (dry matter, sugars, tuber size and desired and undesired constituents). Factory performance relies on recovery, reuse of rejects and avoidance of wastes. Heatmaps drawn of classes of productivity and losses and their attributes reveal where gains are to be made on fields, farms and factories to improve efficiencies, reduce the impact on the environment, and opportunities for decarbonisation., Potato has strong links between the actors as varieties bred by breeders, crop management of growers and site location of processors strongly influence the yield and quality of the finished products. Here, the actors (breeders, growers, processors, retailers and users) in the value chain are recognized, and their information and material flows identified. The influence of genotype, environment and crop management and the efficient use of resources during the production of raw material, tubers harvested for processing purposes, are delineated. It is shown that climate change affects performance and that consumers looking for quality and new products are hardly interested in the primary processes, nor are breeders and processors showing interest in consumer concerns. Crop performance is dependent on yield and quality (dry matter, sugars, tuber size and desired and undesired constituents). Factory performance relies on recovery, reuse of rejects and avoidance of wastes. Heatmaps drawn of classes of productivity and losses and their attributes reveal where gains are to be made on fields, farms and factories to improve efficiencies, reduce the impact on the environment, and opportunities for decarbonisation.

Hybrid breeding may revolutionise the potato world, especially in low- and middle-income countries. The major impact will be on yield in remote and challenging agro-environments. We expect that hybrid breeding will increase the turnover of varieties in those environments when new seed systems based on hybrid true potato seed have been established. With faster breeding and multiplication systems, it is possible to produce clean seed and to respond to climate change as well as rapidly changing market and societal needs. For this revolution to happen, the potato production system (of both seed and ware) needs to be radically changed and such changes are not easy to orchestrate. During the introduction of such a potentially disruptive innovative technology, many actors, stakeholders and institutions play a significant role and each of these parties has its own objectives, interests, and concerns. This concluding chapter aims to answer the question how such a radical innovation can be steered in a societally responsible manner to realise global food security and sustainability in potato production. To guide and coordinate the system innovations triggered by the potential of hybrid potato breeding, strong public-private partnerships are required in different links of the potato value chain.

Potato is an important crop for food security. However, it is very vulnerable to diseases and pests and these are partly seed-borne and therefore transmitted from one generation to the next. Breeding is cumbersome while multiplication is slow. These issues can be solved by a new technology: hybrid breeding based on true potato seed. This book gives an overview of relevant developments in creating new opportunities making use of this technology. This introductory chapter describes the aims of the book, provides a main agenda for debate on this new technology and outlines the structure of the book and briefly indicates the contents of its chapters.

Hybrid true potato seed (HTPS) holds the promise to foster development in potato sectors in East-Africa. Compared to a conventional production system based on clonal propagation of tetraploid varieties, clear advantages of HTPS are easier transport and storage of starting material, high multiplication rates, increased availability of disease-free planting material and faster and more targeted breeding. Despite these advantages, an informed assessment of how HTPS can be implemented into East African seed and farming systems, and of what the enabling conditions are for such implementation is still necessary. Our aim is to understand if and how HTPS could foster development of potato sectors in East Africa and what are the major opportunities and bottlenecks. We describe the context of potato production in East Africa, and we summarise the key lessons from past experiences with the implementation of (non-hybrid) true potato seed. This informs our analysis of the requirements for an effective and inclusive introduction. Major requirements are a solid understanding of: (1) the criteria farmers use to assess the innovation; (2) local farm realties; and (3) the seed system in which farmers operate. The implementation of HTPS requires adaptations in agronomic management and in seed system configurations, but these adaptations need to fit into the agro-ecological and socio-economic context. This can be achieved through an iterative research cycle linking farmers, researchers, breeders and other stakeholders. To facilitate institutional embedding of the innovation, interactive, multi-stakeholder processes are required to develop shared views on the acceptability, sustainability and societal desirability of HTPS. We conclude by drawing a research agenda with urgent questions that need empirical research prior to and during the introduction of HTPS in East Africa.

In this chapter, we describe the technical aspects of hybrid potato breeding, the implications for cultural practices, cropping systems, product development and global food security. Diploid hybrid breeding allows the breeders to focus on selecting the right combination of parents instead of selecting the right clone. Combining the most suitable parents results in homogeneous hybrids that can be tested in different environments. It allows to stack resistance genes, stack complex traits, create uniform offspring, makes breeding results more predictable, the production of a new cultivar much faster and the possibilities for innovative products and value creation much more abundant. However, diploid breeding followed by a seed system based on true potato seed may cause disruptive change, for breeders, regulators and policy makers, seed growers, ware growers, traders, and consumers. The biggest bottlenecks are in the agronomy of growing a crop from very tiny true potato seeds (TPS). Options include direct sowing, producing transplants or producing seedling tubers. A paradigm shift in the production system must create the conditions for a successful hybrid TPS value chain. Many companies and research institutes are now developing hybrid breeding programmes in potato, mostly based on diploid breeding. The potential is huge, including potato production in tropical lowlands on the basis of heat and drought tolerant hybrids, resistance against bacterial diseases and viruses, and high-quality, healthy and innovative potato products, thus contributing to a sustainable, food-secure, productive potato production value chain.

Plant sentience is a hot topic in scientific and popular media. There are moral reasons to respect both the service of plants to humanity and their natural integrity as creatures playing their own significant role in a complex ecosystem. However, to infer that plants have certain cognitive capacities that are present also in certain human and nonhuman animals calls for scientific rigor beyond mere analogy. The unique capacities of plants identified by Segundo-Ortin & Calvo are not necessarily linked to sentience. Nor is it likely that sentience is an evolutionary trait that is present to some extent in all living organisms.

Improving the quality of seed potatoes that smallholder farmers plant continues to represent one of the most important challenges of the potato sector in most developing countries to counter the long-lasting poor yields. This study aimed to better understand the way farmers choose seed potato by exploring the attributes they look for and the benefits they expect from them. We used means-end chains analysis in combination with Kelly’s repertory grid as an elicitation technique and disaggregated data for male and female partners. In total, farmers named 38 attributes they look for when selecting seeds. Farmers associate “good” seeds to those that are well-sprouted, have many eyes, are of a variety they know, are medium in size, are certified, and are undamaged. Most preferred attributes lead to a higher yield and consequently higher income which is the most predominant avenue for farmers to achieve their desired values in life. Female farmers mentioned fewer attributes and also pursued fewer values than their male counterparts. Users and non-users of certified seed were shown to use the same attributes to select their potato seeds. Non-users of certified seed thus seem to be aware of the benefits of certified seed even though they are not using it. The results from this study indicate that increasing the availability of certified seed is not necessarily a straightforward way of improving the quality of seed potato planted by Kenyan smallholder farmers.

In supermarkets in the Netherlands, well over 150 potato products are displayed. They can be distinguished by heating characteristics (boiled or fried), appearance (e.g., intact tuber pieces or formed hash browns), dehydrated (e.g., snacks and flour) and storage temperature (e.g., ambient and frozen). Fancier products (frozen formed versus chilled blanched) require more processes and operations in factories and are more expensive; consumers appreciate them because they offer more convenience. Heatmapping and hierarchical clustering were carried out twice within the domain of classes of products and their attributes. In a theoretical triangulation, consumers give high scores to low prices and a wide range of products, tastes and sizes where processors give these attributes a low score. Processes in factories include dehydration, heating, cooling and transformation. Examples of the latter are modification of starch to increase the range of applications in the food industry, forming of mash and shreds to produce croquettes and hash browns and expansion to make snacks. Processes require operations such as washing, cutting, blanching and packing. In total, between the arrival of the tubers at the gate and leaving as packed products to outlets, 66 operations are distinguished. French fries undergo some 30 operations and to produce flakes, 8 suffice. Heatmapping and hierarchical clustering differentiate a group of physical operations (with attributes associated with heating and cooling that require much energy) and mechanical ones (related to separation, grading, sorting for instance and size reduction of which shredding is an example that require little energy). The wide range of operations in large factories, reducing the moisture content and longtime storage at low temperatures, distinguishes potato from wheat that has fewer operations while increasing the moisture content in relatively small bakeries and the product, bread, stored for about one day in ambient condition

The processing potato ontology includes the three domains of growers, processors and cooks producing tubers, products and dishes, respectively. Dishes consist of three subdomains: types of dishes prepared from products, kitchen operations and consumer preferences. Preparing meals with potato as ingredients dates from the time of the domestication of the crop in the Andes region. It involves washing, peeling, partitioning in smaller sections and heating to gelatinize the otherwise, for non-ruminants, indigestible starch. Since the Columbian Exchange, both the crop and processing expanded globally. The history of potato processing starts with the pre-historic pre-Columbian era when drying as a means to preserve and render the tuber less bulky and making flour and alcoholic drinks were common practice. Once the crop was a global food crop, processing established, initially into an array of nourishments for seafaring and military purposes and later for aviation, convenience and to satisfy hedonistic needs. The domains are studied through a four-tier analysis: first a description and delimitation of the domain are made, next allocation of classes with their attributes followed by awarding a value to an attribute as to the degree it applies to the class, yielding a heatmap, and fourthly, a dendrogram is produced that shows clustering of classes and of attributes with similar features.

The potato is a complex plant. Above-ground it consists of a constellation of stems when grown from a seed tuber, but there is only one stem per seedling grown from true potato seed. Individual stems from both types of starting material can branch below-ground, above-ground at the base of the stem, and by apical branching at the top thus forming a sympodium consisting of stem segments, each ending in an inflorescence. Plants from true seed can branch profusely at the base giving them a bushy appearance. Below-ground branches can develop into stolons that may also branch and can produce several tuber sites and finally tubers. Early leaves are small but later appearing leaves can reach large sizes and are compound. They are imparipinnate with small leaflets between larger pinnae and with the rachis ending in one final top leaflet. This chapter describes in detail the development of the shoot system, the leaves and canopy, the stolon system, the tuber system, the inflorescence structure, and the (relatively weak) root system. It stresses the different fates of tuber incipients and tubers, the relations between above-ground and below-ground development, and the influence of propagule type and physiological age of seed tubers on plant and crop development.

Potato seed degeneration is considered an important seed and yield limiting problem for farmers in Ecuador and other low-income countries. This problem is defined as the process of accumulation of pathogens and pests in/on the seed that occurs when farmers propagate their seed tubers (hereafter seeds) on-farm for successive cycles. The main causes of seed degeneration in Ecuador are Rhizoctonia (Rhizoctonia solani), the Andean weevil (Premnotrypes vorax), Potato virus X, Potato virus S, and purple top disease. The process of seed degeneration could be interacting with different conditions and factors under the farmers’ context such as farmers’ socioeconomic conditions, agroecological conditions, on-farm management practices, and potato varieties. This thesis aims to shed light on these interactions using information collected in the tropical highlands of Ecuador.This thesis began by focusing on purple top, a disease that is spreading in the potato production areas of Ecuador since 2012-2013. A literature review and an innovation history analysis were performed to identify lessons to manage purple top disease. The results showed that stakeholders implemented different initiatives to identify or confirm the causal agent(s), raise funding for research and communication, raise awareness and design management strategies. However, a better coordination and political lobby are necessary to manage this problem. Results showed that it is necessary to strengthen the coordination and communication between stakeholders, the design and implementation of interventions, the acquisition of funding, policies and regulations, and research and surveillance.Subsequently, this thesis focused on how seed degeneration occurs in experiments and farmers’ fields under different agroecological conditions. For this objective, I analysed the information collected during a multi-annual experiment and farmers’ seed surveys. The results showed that agroecological conditions influenced the presence

Global climate change, especially in the view of severe changes in precipitation pattern, is posing a great threat for the agricultural sector, mainly in crops with large water consumption like rice. Major advances have occurred in rice cultivation system to grow rice with lower water input. But the lower yields compared with traditional puddle cultivation is the major disadvantage. It is estimated that there is a need to produce 50% more rice by 2050. To meet this challenge, we need rice varieties with higher yield potential under limited water supply. Therefore, it is important to identify physiological traits to improve drought tolerance and productivity of rice under water limitation. The main goal of this thesis is to compare the physiological basis of drought adaptation among rice genotypes and between rice and wheat.In an initial experiment, rice cultivars adapted to puddle, aerobic and upland ecosystems were compared for their response to drought stress imposed at critical growth stages of the crop.  All cultivars investigated showed significant reduction in yield under drought and the largest reduction was noticed when drought stress coincided with flowering. Comparatively, the aerobic rice cultivar showed higher tolerance irrespective of stage of drought occurrence than lowland and upland cultivars. Upon analysis of the results, reduction in leaf area, increased spikelet sterility and reduced source capacity were seen as the major reasons for the observed yield loss when drought occurred during vegetative, reproductive and grain filling phases, respectively.  At all growth stages, maintenance of photosynthesis contributed to higher yield in the drought tolerant aerobic cultivar.For a specific understanding of drought tolerance at one particular stage, two contrasting rice genotypes were again compared to capture the drought response during grain filling by using a high-throughput phenomics platform and a metabolomics approach. The outcome reveale

Rice (Oryza sativa) is one of the most important cereal crops with high economic and social values. Natural diversity in water-deficit tolerance has allowed rice genotypes to adapt to different edaphic conditions. While genotypes adapted to the irrigated lowland system are most productive, the growing scarcity of freshwater resources for agriculture calls for developing rice genotypes that can be gown like dryland cereals. This dissertation aims to understand why so far rice cannot perform well under drier conditions via studying the basic anatomical, morphological and physiological mechanisms that determine the comparative adaptability of rice and wheat (Triticum aestivum) to water deficit.First, leaf anatomical and morphological attributes that affect leaf photosynthesis (An) and transpiration efficiency (TE) were investigated, using six representative rice genotypes and two wheat genotypes grown under long-term water deficit. Variations in An and TE were well explained by the CO2 diffusion components, i.e. stomatal conductance (gs) and mesophyll conductance (gm). Genotypic variation in gs among rice genotypes resulted from the differences in stomal density and size. Compared with wheat, the lower gm in rice was associated with its less optimized leaf mesophyll structures and anatomical properties.Secondly, anatomical traits that affect the acquisition and transport of water in root and shoot were examined at two developmental stages of three rice and two wheat genotypes. Rice roots possess extensive aerenchym but much smaller xylem vessels than wheat roots, while the xylem area in stem and leaf was higher in rice than in wheat. Compared with wheat, water deficit clearly induced the apoplastic barriers for radial water flow in rice roots and strongly limited the root growth and lateral root proliferation in rice, whereas the shoot growth in rice was less affected by treatments. As a result, there was an imbalance between water acquisition and transpiration demand

Progressively erratic monsoon patterns threaten the ability of the rice-wheat system in South Asia’s Eastern Gangetic Plains to provide food and livelihoods for their food insecure and impoverished people. Ongoing research has identified early crop planting and improved irrigation use as key entry-points to overcome these challenges. However, there are critical knowledge gaps on the complex feedback mechanisms of these activities resulting in their low and incomplete adoption. These feedback mechanisms comprise of intertwined factors beyond classic water challenges in the rice-wheat system, including temperature rise, pest and disease pressure, value chains, and policy discrepancies between household and national scales. This thesis investigates and evaluates farmers’ planting and irrigation activities in the rice-wheat system through a socio-ecological systems framework to fill the knowledge gaps – thus identifying constraints and opportunities to overcome water-related challenges for food security and poverty reduction. Empirical data on farmers’ perspectives of planting and irrigation activities were collected and analysed – indicating that farmers and policymakers alike aim to synchronize crop planting with the monsoon onset, but that irrigation use at planting and during in-season dry spells is frequently delayed by uncertainty in weather signals, groundwater availability and availability of other inputs. Simulated crop yield patterns were then used to indicate the potential of synchronizing rice planting with the monsoon onset and fully utilizing irrigation to buffer against drought to contribute to food security. The results suggest that this strategy may indeed increase productivity and resilience in the Eastern Gangetic Plains – but not in the Western Gangetic Plains. However, an analysis of large-scale household survey data on crop production indicate that the poverty reduction potential of productivity increases is limited to the largest farmers, while mo

Over the last 50 years, seed production of oilseed rape (Brassica napus L.), the source of one of the healthiest edible oils for human consumption, has increased globally, reaching 71 million tonnes in 2017. However, food security will be challenged by the growth of the world’s population, reaching 9.7 billion people in the next 50 years, increasing the demand for food, vegetable oils for human consumption, feed, and biofuel. Therefore, new strategies are urgently needed to satisfy the growing demand for oilseed rape, and one such strategies revolves around making use of plasticity in oilseed rape. The overall objective of this thesis was to evaluate the plastic response of oilseed rape to environmental factors and agronomic practices by identifying the main drivers and mechanisms underlying plant C and N distribution, with emphasis in the interaction between plant C status with plant architectural traits and physiological traits associated with seed yield. In this study, N fertilizer supply determined N content per unit of leaf mass (Nmass), while it played a subordinate role in altering N per unit of area (Narea), which was the main determinant of C assimilation. The rate of photosynthesis per unit of leaf area was strongly correlated with N content per leaf area (Narea) through an asymptotical relationship. Narea was more closely associated with leaf mass per unit of leaf area (LMA) than with Nmass. LMA was affected by a significant interaction between N supply and plant population density. Such an interaction plays an important role in the discrepancies observed in literature. Leaf area was affected by N supply, with important effects on light distribution and C assimilation at crop level. Indeed, the interaction between N supply and plant population density influences the leaf area index, which determines the proportion of light intercepted by the plant canopy. The role of N supply as determinant of plant source-sink status (which is, in turn, the main de

Integrated Pest Management (IPM) was developed in response to the crisis caused by unrestricted use of pesticides. The IPM concept matured over time and today, it stands on a  solid conceptual basis and millions of farmers across the globe, especially in developing countries, have been trained in it through the Farmers’ Field School approach. Nevertheless, adoption rate remains frustratingly low. This thesis tries to understand why IPM is so  difficult to implement for smallholder farmers in developing countries and what is needed to make IPM work for them. Eggplant production in Bangladesh was taken as a case and it involved various disease and insect problems. Involving farmers in the research, this study aimed to craft IPM options for farmers that could function in their context, that maximally use natural enemies and that significantly reduce pesticide use. It also assessed the possible reasons for IPM research failures and possible factors contributing to the success or failure of the crafted IPM.Farmers participated through interviews, group discussions and field experimentation in tailoring IPM. Negotiations and discussions with these farmers were used to get a better grip on the underlying complexity of all tested IPM options that might hamper adoption. Moreover, a few in vitro and screen house studies were carried out to identify the source of infection of the diseases and to disentangle relative roles of selected IPM components in reducing infections. For each of the disease and insect problems, farmers’ conventional practice of spraying proved ineffective. In contrast, a combination of IPM options proved technically sound and economically viable. However, bottlenecks to scale out these IPM options still remain. For damping-off (caused by several pathogens), soil application of Trichoderma harzianum (T. harzianum) in the nursery combined with seed treatment with hot water was effective, producing 25-64 percentage points more healthy seedling

Despite previous attempts by governmental, non-governmental and research organizations, potato late blight and bacterial wilt are still rampant in Ethiopia, compromising potato production in the country. This thesis starts with the argument that to be able to effectively manage such disease, it is imperative to have a fresh perspective and a deep enough understanding of the problem situation which, in turn, can inform the type of disease management strategy that needs to be put in place. With this objective in mind, the study set out to understand the problem of late blight and bacterial wilt with a social-technical lens, and to explore the roles that different social-technical interventions play in the management of crop diseases, particularly late blight. Consequently, the first two empirical chapters (Chapters 2 and 3) of the diagnostic phase examine the multidimensional problem situation of late blight and bacterial wilt management. In the intervention phase (Chapters 4 and 5), different types of learning and communicative interventions are studied.The central tenet of Chapter 2 is that the management of late blight and bacterial wilt is a complex problem, and that addressing complex challenges require actors to understand the multi-dimensional problem aspect of crop diseases, such as late blight and bacterial. The study assesses actors’ understanding of the technical and institutional dimensions of the complex problem situation of late blight and bacterial wilt management, and how their understanding of the situation facilitates or hinder collective action in the management of the two diseases. The chapter highlights how actors essentially overlooked key systemic problems while their management responses are mainly geared towards uncoordinated short-term reactions. Limited recognition of interdependency and a generally top-down intervention approach stand out to be key systemic factors. The chapter concludes that a bottom-up and participatory disease management

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 appr

Effective management of crop diseases is a key precondition for sustainable crop production and to improve food security globally. However, learning approaches that improve smallholder farmers’ knowledge, perceptions, and practices to deal with crop diseases by fostering social and technical innovations are seldom studied. A study was conducted to examine: (1) how a combination of experiential and social learning approaches influences potato farmers’ knowledge, perceptions, and practices in bacterial wilt and its management in Ethiopia and (2) the implications of combining the two approaches for complex crop disease management in smallholder context. Data were derived from face-to-face in-depth interviews, reflective workshops, and participant observations. The findings showed that farmers’ knowledge and perceptions about disease incidence, the pathogen that causes the disease, its spreading mechanisms, host plants, and disease diagnosis were changed. Farmers’ practices in management of the disease were also improved. Learning about the cause of the disease stimulated the identification of locally relevant spreading mechanisms and the feasibility of a range of recommended disease management methods. Moreover, farmers recognized their interdependency, role, and responsibility to cooperate to reduce the disease pressure in their community. We conclude that learning interventions aiming to improve smallholder farmers’ knowledge, perceptions, and practices to deal with complex crop diseases need to combine experiential and social learning approaches and consider farmers’ local knowledge.