Abundance of pests and diseases in Arabica coffee production systems in Uganda - ecological mechanisms and spatial analysis in the face of climate change.

Coffee production worldwide is threatened by a range of coffee pests and diseases (CPaD). Integrated management options require an understanding of the bioecology of CPaD and the prevalent interdependencies within the agroecological context. The comparison of different shading systems (e.g. shade-grown vs. sun-grown coffee) and the identification of tradeoffs for ecosystem services is still a matter of ongoing debates. There is little quantitative knowledge of field-level investigation on shade effects and its ecological mechanisms across environmental and shading system gradients. Considering the increasingly evident effects of progressive climate change on CPaD, the need to examine the balance of shade effects under different environmental conditions becomes apparent. With the example of the coffee growing region of Mt Elgon, Uganda, this project aimed at addressing the complexity of shading effects on economically relevant CPaD using environmental and production system gradients. The approach was designed in an interdisciplinary manner, to involve the broader context of coffee agroforestry systems. The first two chapters of this thesis dealt with general aspects of coffee smallholder farming. The diversity of existing coffee production systems was characterized along an altitudinal gradient. A typology of production systems based on indicators related to the vegetation structure was generated and classified as coffee open canopy, coffeebanana inter-cropping, and densely shaded coffee systems. The typology served as the basis for comparison across the environmental and production system gradients. In the second chapter, farmers’ knowledge on CPaD and the role of shade trees was contrasted with expert knowledge and field observations. Discrepancies regarding CPaD symptomatology, management and response to shade were revealed. Tackling institutional obstacles and disentangling shading effects are therefore a priority for the improvement of plant health management. The last two chapters focused more specifically on biophysical aspects of Coffee Leaf Rust (CLR, Hemileia vastatrix) and White Coffee Stem Borer (WCSB, Monochamus leuconotus). The effects of environment and production system on CLR abundance were spatio-temporally variable and either directly, interactive or indirectly mediated by microclimate. The development of white coffee stem borer was controlled by the bimodal rainfall, and by altitude and shade through their effect on minimum temperature. The findings emphasize the enormous importance of micro-environments for the ecology of CPaD, not least because of its implications in the context of climate change

El canvi climàtic posa en perill el cafè i el cacau

PER A MOLTES PERSONES, beure cafè i menjar xocolata és un autèntic plaer. Tant les plantes de cafè com les de cacau es cultiven en unes zones molt concretes de la Terra, als cinturons tropicals, i en teoria representen una font de riquesa per als països productors. Tanmateix, la demanda creixent, combinada amb els efectes del canvi climàtic i les desigualtats econòmiques entre productors i consumidors, posen en perill aquests cultius. Així ho indiquen dos estudis publicats a la revista Plos One i un altre a Current Biology, que suggereixen que per mantenir la productivitat actual cal incrementar la diversitat genètica d"aquestes plantes i afavorir un model de comerç just

Towards a collaborative research: A case study on linking science to farmers' perceptions and knowledge on Arabica coffee pests and diseases and its management

The scientific community has recognized the importance of integrating farmer's perceptions and knowledge (FPK) for the development of sustainable pest and disease management strategies. However, the knowledge gap between indigenous and scientific knowledge still contributes to misidentification of plant health constraints and poor adoption of management solutions. This is particularly the case in the context of smallholder farming in developing countries. In this paper, we present a case study on coffee production in Uganda, a sector depending mostly on smallholder farming facing a simultaneous and increasing number of socio-ecological pressures. The objectives of this study were (i) to examine and relate FPK on Arabica Coffee Pests and Diseases (CPaD) to altitude and the vegetation structure of the production systems; (ii) to contrast results with perceptions from experts and (iii) to compare results with field observations, in order to identify constraints for improving the information flow between scientists and farmers. Data were acquired by means of interviews and workshops. One hundred and fifty farmer households managing coffee either at sun exposure, under shade trees or inter-cropped with bananas and spread across an altitudinal gradient were selected. Field sampling of the two most important CPaD was conducted on a subset of 34 plots. The study revealed the following findings: (i) Perceptions on CPaD with respect to their distribution across altitudes and perceived impact are partially concordant among farmers, experts and field observations (ii) There are discrepancies among farmers and experts regarding management practices and the development of CPaD issues of the previous years. (iii) Field observations comparing CPaD in different altitudes and production systems indicate ambiguity of the role of shade trees. According to the locality-specific variability in CPaD pressure as well as in FPK, the importance of developing spatially variable and relevant CPaD control practices is proposed. (Résumé d'auteur

First report of the infection of insecticide-resistant malaria vector mosquitoes with an entomopathogenic fungus under field conditions

BACKGROUND: Insecticide-resistant mosquitoes are compromising the ability of current mosquito control tools to control malaria vectors. A proposed new approach for mosquito control is to use entomopathogenic fungi. These fungi have been shown to be lethal to both insecticide-susceptible and insecticide-resistant mosquitoes under laboratory conditions. The goal of this study was to see whether entomopathogenic fungi could be used to infect insecticide-resistant malaria vectors under field conditions, and to see whether the virulence and viability of the fungal conidia decreased after exposure to ambient African field conditions. METHODS: This study used the fungus Beauveria bassiana to infect the insecticide-resistant malaria vector Anopheles gambiae s.s (Diptera: Culicidae) VKPER laboratory colony strain. Fungal conidia were applied to polyester netting and kept under West African field conditions for varying periods of time. The virulence of the fungal-treated netting was tested 1, 3 and 5 days after net application by exposing An. gambiae s.s. VKPER mosquitoes in WHO cone bioassays carried out under field conditions. In addition, the viability of B. bassiana conidia was measured after up to 20 days exposure to field conditions. RESULTS: The results show that B. bassiana infection caused significantly increased mortality with the daily risk of dying being increased by 2.5 × for the fungus-exposed mosquitoes compared to the control mosquitoes. However, the virulence of the B. bassiana conidia decreased with increasing time spent exposed to the field conditions, the older the treatment on the net, the lower the fungus-induced mortality rate. This is likely to be due to the climate because laboratory trials found no such decline within the same trial time period. Conidial viability also decreased with increasing exposure to the net and natural abiotic environmental conditions. After 20 days field exposure the conidial viability was 30%, but the viability of control conidia not exposed to the net or field conditions was 79%. CONCLUSIONS: This work shows promise for the use of B. bassiana fungal conidia against insecticide-resistant mosquitoes in the field, but further work is required to examine the role of environmental conditions on fungal virulence and viability with a view to eventually making the fungal conidia delivery system more able to withstand the ambient African climate

Modelling spatial variability of coffee (Coffea Arabica L.) crop condition with multispectral remote sensing data.

Doctor of Philosophy in Environmental Science. University of KwaZulu-Natal, Pietermaritzburg, 2017.Abstract available in PDF file

Cochonilhas-algodão associadas ao cafeeiro em estufas

Mestrado em Engenharia Agronómica - Instituto Superior de AgronomiaThe main objective of Centro de Investigação das Ferrugens do Cafeeiro, Instituto de Investigação Científica Tropical (CIFC/IICT) is to contribute for the development of coffee varieties resistant to coffee leaf rust, Hemileia vastatrix. Mealybugs are a major phytossanitary problem of coffee varieties maintained by CIFC/IICT, due to their interference with the production of young coffee leafs necessary for the inoculation of fungi. The aims of the present work were: a) to identify the mealybug species associated with commercial varieties of coffee, such as Catimor and Sarchimor, in the greenhouses of CIFC/IICT; b) to study the dynamics of infestation of Planococcus citri in the varieties Catimor and Sarchimor, under greenhouse conditions; c) to compare the colonization rate and development of P. citri in two coffee genotypes, one resistant to coffee leaf rust (Catimor CIFC 45) and one susceptible (Caturra vermelho CIFC 19/1). Two species of mealybugs were identified, Phenacoccus madeirensis and P. citri. The variety Catimor was the most susceptible to P. citri. No significant differences were observed in the development time of P, citri among the studied varieties. Nevertheless, the rate of colonization by mealybugs was higher in Caturra CIFC 19/

Prediction of insect pest distribution as influenced by elevation: Combining field observations and temperature-dependent development models for the coffee stink bug, Antestiopsis thunbergii (Gmelin)

The antestia bug, Antestiopsis thunbergii (Gmelin 1790) is a major pest of Arabica coffee in Africa. The bug prefers coffee at the highest elevations, contrary to other major pests. The objectives of this study were to describe the relationship between A. thunbergii populations and elevation, to elucidate this relationship using our knowledge of the pest thermal biology and to predict the pest distribution under climate warming. Antestiopsis thunbergii population density was assessed in 24 coffee farms located along a transect delimited across an elevation gradient in the range 1000–1700 m asl, on Mt. Kilimanjaro, Tanzania. Density was assessed for three different climatic seasons, the cool dry season in June 2014 and 2015, the short rainy season in October 2014 and the warm dry season in January 2015. The pest distribution was predicted over the same transect using three risk indices: the establishment risk index (ERI), the generation index (GI) and the activity index (AI). These indices were computed using simulated life table parameters obtained from temperature-dependent development models and temperature data from 1) field records using data loggers deployed over the transect and 2) predictions for year 2055 extracted from AFRICLIM database. The observed population density was the highest during the cool dry season and increased significantly with increasing elevation. For current temperature, the ERI increased with an increase in elevation and was therefore distributed similarly to observed populations, contrary to the other indices. This result suggests that immature stage susceptibility to extreme temperatures was a key factor of population distribution as impacted by elevation. In the future, distribution of the risk indices globally indicated a decrease of the risk at low elevation and an increase of the risk at the highest elevations. Based on these results, we concluded with recommendations to mitigate the risk of A. thunbergii infestation