A. Chevallier, O. Bray, J.P. Prunet, M. Giraud
Walnut blight, due to Xanthomonas arboricola pv. juglandis (Xaj), is one of the most important diseases of walnut trees (Juglans regia). It is responsible for significant crop losses which can reach more than 50% of nut drops. In south western France, disease management has relied upon 3 to 4 copper compound sprays applied from bud break to female flowering. However, this strategy is often ineffective and no other solution has yet been found. Moreover, there is a lack of knowledge on disease development. Thus, we tried to better understand the different factors which could influence the development of walnut blight. We compared two orchards, one with a high sensitivity to walnut blight, and one with a low sensitivity. The results confirm that difference. The 2008 climatic conditions, quite similar in the two orchards, do not seem to be the most influencing factor of the disease development. Similarly, water stress did not affect the emergence and development of symptoms. Xaj populations were higher in the sensitive orchard but do not explain the difference of walnut blight sensitivity between orchards. Finally, soil and crop management, seem to have a huge influence. These factors must also play a role in the production of phenolic compounds (Flavonoids and HCA) which was higher in the low sensitive orchard. That confirms their protective role against external diseases attacks.
Chevallier, A., Bray, O., Prunet, J.P. and Giraud, M. (2010). FACTORS INFLUENCING WALNUT BLIGHT SYMPTOMS EMERGENCE AND DEVELOPMENT. Acta Hortic. 861, 473-478
DOI: 10.17660/ActaHortic.2010.861.67
Xanthomonas arboricola pv. juglandis, fungus, soil, orchard management, phenolic compounds, climate

Acta Horticulturae