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Impact of climate on a host-hyperparasite interaction on Arabica coffee in its 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]
  1. Natural enemies of plant pathogens might play an important role in suppressing plant disease levels in natural and agricultural systems. Yet, plant pathogen-natural enemy interactions might be sensitive to changes in the climate. Understanding the relationship between climate, plant pathogens, and their natural enemies is thus important for developing climate-resilient, sustainable agriculture.
  2. To this aim, we recorded shade cover, daily minimum and maximum temperature, relative humidity, coffee leaf rust, and its hyperparasite at 58 sites in southwestern Ethiopia during the dry and wet season for two years
  3. Coffee leaf rust severity was positively related to maximum temperature and hyperparasite severity was higher when the minimum temperature was low (i.e. in places with cold night temperatures) during three of the four surveying periods. While canopy cover did not have a direct effect on rust severity, it reduced rust severity indirectly by lowering the maximum temperature. Canopy cover had a direct positive effect on hyperparasite severity.
  4. Synthesis and applications. Our findings highlight that coffee leaf rust and its hyperparasite are both affected by shade cover and temperature, but in different ways. On the one hand, these niche differences between coffee leaf rust and its hyperparasite provide opportunities to develop strategies to manage the environment (such as shade cover and microclimate) in such a way that the rust is disfavored and the hyperparasite is favored. On the other hand, these niche differences lead to the worrying prediction that levels of coffee leaf rust will increase, and its hyperparasite will decrease, with climate change.
Keywords [en]
Canopy cover, climate change, coffee leaf rust, Hemileia vastatrix, Lecanicillium lecanii, minimum and maximum temperature, relative humidity
National Category
Agricultural Science
Research subject
Ecology and Evolution
Identifiers
URN: urn:nbn:se:su:diva-216218OAI: oai:DiVA.org:su-216218DiVA, id: diva2:1749718
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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