Modelling the effects of temperature and leaf wetness on monocyclic infection in a tropical fungal pathosystem

International audienceModelling the epidemiology of water yam anthracnose (Dioscorea alata) caused by the fungus Colletotrichum gloeosporioides is an important research goal, as it will allow the investigation of a wide range of scenarios of new practices to reduce the disease impact before experimentation in the field. Developing such a model requires a prior knowledge of the fungus’s response to the environmental conditions, which will be affected by pest management. In this work, we first measured the response of the fungus to the main physical environmental factors controlling its development, namely temperature (ranging from 18 °C to 36 °C) and wetness duration (from 2 h to 72 h). As response variables, we measured the percentage of formed appressoria (relative to the total number of spores), the length of the latent period (time lag between inoculation and first symptoms observed), and the rate of necrotic lesion extension (percentage of diseased leaf surface at different time steps). These variables allow us to estimate the effects of temperature and wetness duration on the success of infection (appressoria formation) and the subsequent rate of disease development (latent period length and lesion extension rate). The data were fitted to non-linear models chosen for their ability to describe the observed patterns. From our data and model analyses, we were able to estimate parameters such as the optimal and maximal temperatures (25–28 °C and 36 °C, respectively), the required wetness duration to reach 20 % of infection success and the time to reach 5 % disease severity as a function of temperature

Evaluation du rôle des phases dissoutes et particulaires dans la contamination en Chlordécone en rivière

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Co-Design and Experimentation of a Prototype of Agroecological Micro-Farm Meeting the Objectives Set by Climate-Smart Agriculture

Developing climate-smart agriculture is an urgent necessity to ensure the food security of a growing global population, to improve the adaptation of agricultural systems to climatic hazards, and to reach a negative carbon balance. Different approaches are being explored to achieve those objectives, including the development of new technologies for efficiency improvements to current systems and substitution of chemical inputs by bio-inputs, but the urgency of the climatic, social, and environmental context calls for more disruptive actions to be taken. We propose an approach to the design of climate-smart production systems structured in four steps: (1) diagnosis of the study region on the basis of the three pillars of climate-smart agriculture, (2) co-design of a disruptive system only based on agroecological and bioeconomic principles, (3) long-term experimentation of this system, and (4) in itinere adjustment of the system based on collected data and on-field evaluations with agricultural stakeholders. The outcome of this approach is the agroecological microfarm named KARUSMART, settled in 2018 on one hectare in the North Basse-Terre region of Guadeloupe (F.W.I.). This study presents its co-design and experimentation stages as well as the first performance results. At the end of the first two years, this microfarm showed a clear improvement in 15 of the 19 indicators used to evaluate the performance of the actual farming systems in the study region. Among the most striking results are a clear superiority in nutritional performance from 3 pers.ha−1 to 8 pers.ha−1 and a reduction in GHG balance from +2.4 tCO2eq.ha−1 to −1.1 tCO2eq.ha−1 for the study area and the microfarm, respectively. These results are promising for developing climate-smart agricultural systems and need to be consolidated further through longer-term monitoring data, the implementation of more similar systems in the study area, and the implementation of the design principles in other contexts

Monitoring agricultural pollutions from the catchment area to coastal areas

International audienceCoastal marine environments are particularly exposed to pollutants emanating from human activities such as agriculture. Phytosanitary products follow the path of the water cycle, reaching rivers and aquifers, then coastal waters through run-off, infiltrations and resurgences. « OPALE » is an observatory dedicated to the monitoring of agricultural pollutions at the scale of the rivers Pérou-Père catchment area, located in Guadeloupe (Lesser Antilles). The main objectives of OPALE are to monitor and make available data on contamination levels and study the transfer of pollutants between the different aquatic compartments (surface waters, groundwaters and coastal waters)

Monitoring agricultural pollutions from the catchment area to coastal areas

International audienceCoastal marine environments are particularly exposed to pollutants emanating from human activities such as agriculture. Phytosanitary products follow the path of the water cycle, reaching rivers and aquifers, then coastal waters through run-off, infiltrations and resurgences. « OPALE » is an observatory dedicated to the monitoring of agricultural pollutions at the scale of the rivers Pérou-Père catchment area, located in Guadeloupe (Lesser Antilles). The main objectives of OPALE are to monitor and make available data on contamination levels and study the transfer of pollutants between the different aquatic compartments (surface waters, groundwaters and coastal waters)

Flow patterns and pathways of legacy and contemporary pesticides in surface waters in tropical volcanic catchments

Severe water pollution issues due to legacy and contemporary pesticides exist in tropical regions and are linked to cash crops requiring intensive plant protection practices. This study aims to improve knowledge about contamination routes and patterns in tropical volcanic settings to identify mitigation measures and analyse risk. To this aim, this paper analyses four years of monitoring data from 2016 to 2019 of flow discharge and weekly pesticide concentrations in the rivers of two catchments grown predominantly with banana and sugar cane in the French West Indies. The banned insecticide chlordecone, applied in banana fields from 1972 to 1993, was still the major source of river contamination, while the currently used herbicide glyphosate, its metabolite aminomethylphosphonic acid (AMPA), and postharvest fungicides also exhibited high contamination levels. A value of 0.5 of the Gustafson Ubiquity Score (GUS) was shown to separate contaminant and noncontaminant pesticides, indicating a high vulnerability to pollution by pesticides in this tropical volcanic context. The patterns and routes of river exposure to pesticides differed markedly between the pesticides in accordance with the hydrological behaviour of volcanic islands and the history and nature of pesticide uses. Concerning chlordecone and its metabolites, observations confirmed previous findings of a main subsurface origin of river contamination by this compound but also showed large erratic short-term variations, suggesting the influence of fast surface transport processes such as erosion for legacy pesticides with large sorption capacity. Concerning herbicides and postharvest fungicides, observations have suggested that surface runoff and fast lateral flow in the vadose zone control river contamination. Accordingly, mitigation options need to be considered differently for each type of pesticide. Finally, this study points out the need for developing specific exposure scenarios for tropical agricultural contexts in the European regulation procedures for pesticide risk assessment