WALNUT BLIGHT AND APICAL NECROSIS

Walnut blight, Xanthomonas campestris pv. juglandis, is a serious disease, which can destroy up to 50 % of the yield of a walnut orchard. The nuts react to a bacterial attack by the formation of parietal or apical necrosis, then they drop before reaching maturity. These defense mechanisms of the plant, which utilize phenolic compounds such as juglone and its glucoside, can be induced even in the presence of very low populations of bacteria. Then necrosis usually develops starting from the pistillar point of the fruit. Traditional copper treatments are often ineffective in such cases, and can even worsen the situation by an accumulation of copper in the soil. An investigation was carried out on about fifty sites in the south-east of France to try to characterize the factors which have an influence on the severity of necrosis. The factors taken into account are the physicochemical composition of the soil, the content of major elements and trace elements in leaves, the fertilization on the site and the number of copper treatments applied. The statistical analysis of the results from the investigation reveals elements for further study to try to decrease losses in harvest. The first results from these experiments are presented and commented on.

IV International Walnut Symposium

A. Garcin, D. Duchesne

walnut, Xanthomonas campestris pv. Juglandis, fruit necrosis.

https://doi.org/10.17660/ActaHortic.2001.544.50