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Impact of climate and management on coffee berry disease and yield in Arabica coffee’s native range
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.ORCID iD: 0000-0002-4658-7850
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.ORCID iD: 0000-0002-1215-2648
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Climate change might increase plant diseases, reduce crop yields and threaten the livelihoods of millions of smallholder farmers globally. It is thus important to understand the relationships between climate, disease levels and yield to improve management strategies for sustainable agroforestry in a changing climate. One of the major threats to coffee production in Africa is coffee berry disease, caused by the fungal pathogen Colletotrichum kahawae. To investigate the effects of climatic and management variables on coffee berry disease and yield, we recorded daily minimum and maximum temperature and relative humidity, as well as incidence of coffee berry disease and yield in 58 sites along a broad environmental and management gradient in southwestern Ethiopia in both 2018 and 2019. Coffee berry disease was affected by several climatic and management variables, with relatively high consistency between years. For example, coffee berry disease incidence was higher in sites with high minimum temperatures during the fruit expansion stage from March to April, and was lower in sites with high minimum temperatures during the endosperm filling stage from May to June. Coffee berry disease incidence was negatively affected by the proportion of resistant cultivars, whereas management intensity had no effect on disease incidence. Coffee yield decreased with increasing minimum and maximum temperatures during the flowering period in 2018 and the fruit developmental period in 2019, respectively. Coffee yield was negatively affected by canopy cover, and positively affected by management intensity, in both years. Our findings highlight that coffee berry disease and yield were affected by different climatic and management variables. Yet, managing for low disease-high yield is practically difficult, as the effect of several climatic variables was season-dependent, and at the same time climatic variables were highly correlated between seasons. One way to break the correlation of climatic variables between seasons might be to take advantage of differences among shade trees in the presence or timing of leaf drop. To reduce levels of coffee berry disease, an effective strategy is to use resistant cultivars, but this might threaten the wild coffee genetic reservoir.

Keywords [en]
Climate change, coffee berry disease, management intensity, minimum and maximum temperature, relative humidity, yield
National Category
Agricultural Science
Research subject
Ecology and Evolution
Identifiers
URN: urn:nbn:se:su:diva-216212OAI: oai:DiVA.org:su-216212DiVA, id: diva2:1749717
Available from: 2023-04-11 Created: 2023-04-11 Last updated: 2023-04-12
In thesis
1. The relationship between climate, disease and coffee yield: optimizing management for smallholder farmers
Open this publication in new window or tab >>The relationship between climate, disease and coffee yield: optimizing management for smallholder farmers
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Climate change and diseases are threatening global crop production. Agroforestry systems, which are characterized by complex multispecies interactions, are considered to provide nature-based solutions for climate change mitigation and pest and disease regulation. Understanding the role of the abiotic environment and species interactions in shaping diseases and yield in agroforestry systems would enable us to develop effective ecologically-informed pest and disease management under a changing climate, support sustainable agricultural practices, and maximize the benefits gained from agroforestry systems. To gain such a comprehensive understanding of what shapes pest and disease levels and yield in agroforestry systems, we need to investigate how the interactions between agroforestry system components, such as trees, crops and their associated organisms, vary in space and time, and how they are influenced by abiotic factors in terms of pests and diseases and yield. 

In this thesis, my overarching goal was to understand how microclimate and management impact major coffee pests and diseases, their natural enemies, and coffee yield, as well as farmers’ perceptions of climate change and climate-mediated changes in disease dynamics and yield, with the aim of using these insights to optimize management decisions for smallholder farmers in southwestern Ethiopia. With this aim, I selected 58 sites along a gradient of management intensity, ranging from minimal management in the natural forest to moderate management in smallholder farms and intensive management in commercial plantations. As an approach, I combined observational and interview studies to examine i) the impact of shade tree species identity and canopy cover on coffee pests and diseases, ii) the effect of climate and management on coffee berry disease and yield, iii) the impact of climate on a host-hyperparasite interaction, and iv) farmers’ perceptions of climate change and climate-mediated changes in disease dynamics and yield. 

I found that tree identity affected the incidence and severity of coffee diseases, whereas insect pests were strongly affected by canopy cover, but in a species-specific way (I).  Both climate and management affected coffee berry disease and yield. Importantly, the effect of climatic variables on disease and yield differed strongly between the developmental stages from flowering to ripening (II). In chapter (III), I found that the climatic niches of coffee leaf rust and its hyperparasite differed, with coffee leaf rust severity preferring high maximum temperatures, whereas the hyperparasite preferred cold nights. The interviews revealed that the majority of farmers perceived long-term changes in one or more aspects of the climate, and the majority of farmers perceived an increase in coffee leaf rust and a decrease in coffee berry disease. Climate data also supported farmers’ knowledge on climate-disease-yield relationships (IV). 

Taken together, my thesis advances our understanding of the relationship between climate and management of coffee pests, diseases and yield, and this may contribute to the development of ecologically-informed pest and disease management strategies for coffee production and other agroforestry crops.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2023. p. 48
Keywords
Agroforestry, Arabica coffee, climate change, fungal disease, host-hyperparasite interaction, insect pest, minimum temperature and maximum temperature, shade cover, shade tree species, smallholder farmers, yield
National Category
Agricultural Science
Research subject
Ecology and Evolution
Identifiers
urn:nbn:se:su:diva-216221 (URN)978-91-8014-278-6 (ISBN)978-91-8014-279-3 (ISBN)
Public defence
2023-05-31, Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, Stockholm, 10:00 (English)
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Available from: 2023-05-08 Created: 2023-04-10 Last updated: 2023-04-24Bibliographically approved

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Nurihun, Biruk Ayalew

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