How hedgerow characteristics alter pseudocercospora fijiensis dispersal?

Delatouche Lucile, Tixier Philippe, Sainte-Rose Jérôme Laurent, Daribo Marie Odette, De Lapeyre de Bellaire Luc. 2022. How hedgerow characteristics alter pseudocercospora fijiensis dispersal?. In : Book of abstracts: XVII Congress of the European Society for Agronomy. ESA. Müncheberg : ZALF, p. 309. Congress of the European Society for Agronomy. 17, Potsdam, Allemagne, 29 Août 2022/2 Septembre 2022.

Résumé : Diversification of agrosystems is often presented as an important lever for pest management. However, there is very little knowledge about the effect of this diversification on disease dynamics. Because of their size, trees and hedgerows have the potential to alter the dispersal of aerial diseases. Black Leaf Steak Disease (BLSD) caused by Pseudocercospora fijiensis is the main disease of bananas and leads to significant crop losses and environmental concerns due to fungicide applications. In this work, we have experimentaly evaluated how hedgerows influence the dispersal of two types of spores involved in short (conidia) and long-distance (ascospore) dispersion of BLSD. Our aim was to determine how hedgerow characteristics interfere with spore dispersion. We set-up 21 experiments on 7 contrasted hedgerows, with no sources of BLSD in the 400 m radius around. Each experiment consisted in i) placing an artificial source of one type of spores on one side of the hedgerow, and ii) on both side a set of 25 banana trap plants (i.e. 50 cm high vitro-plant) in line of 5 at equal distances to the source of spores until 50 meters. Banana plants were exposed during 10 days (corresponding to the time of emergence of one leaf). After exposure in the field, each banana plant was settled in an individual greenhouse in order to favour disease expression in a humid environment during 2-times the incubation period. Then the density of BLSD lesions was measured on the leaf that emerged during exposure. Using linear models, we analysed the density of BLSD lesions on each banana tree including four factors: i) the wind (frequency of wind directed between the source of spores toward each given plant), ii) the distance between the banana plant and the source of BSLD, iii) the side of the hedgerow (i.e. on the side of the source or not), and iv) the characteristics of the hedgerow (including their height, width, porosity, that were summarized in a capacity of interception variable). For ascospore dispersal, there was no massive difference between sides control and test (respectively, without and with hedgerow). However, there was a strong effect of the characteristic of the hedgerows on the BLSD lesion. As expected, the lesion density decreased with the distance to the source. There was a maximal dispersion of spores for medium winds, while it was lower for lowest or strongest winds. Our results is the first quantification of the effect of hedgerows on BLSD dynamics. Interestingly, there was a strong effect of the hedgerow presence characteristics (capacity of spore interception) on the dispersion of the disease, i.e. the higher the capacity of interception the lower the dispersion. There was up to 50% decrease of lesion density between small and large capacity of interception hedgerows. Our results also provide a quantification of the dispersal capacity of the two types of spores and the influence of the wind. This study gives key information to better include hedgerows in agroecological control against BLSD and fungal diseases in general.

Auteurs et affiliations

• Delatouche Lucile, CIRAD-PERSYST-UPR GECO (FRA) ORCID: 0000-0002-1309-7986
• Tixier Philippe, CIRAD-PERSYST-UPR GECO (FRA) ORCID: 0000-0001-5147-9777
• Sainte-Rose Jérôme Laurent, CIRAD-PERSYST-UPR GECO (MTQ)
• Daribo Marie Odette, CIRAD-PERSYST-UPR GECO (MTQ)
• De Lapeyre de Bellaire Luc, CIRAD-PERSYST-UPR GECO (FRA) ORCID: 0000-0003-1243-0887

Source : Cirad-Agritrop (https://agritrop.cirad.fr/603291/)

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