A THREE YEAR STUDY ON THE EFFECT OF CHELAL^® KUBIG ON THE REDUCTION OF NECROTIC WALNUT FALLS

Walnut blight is one of the most serious fruit and foliar diseases of Walnut trees (Juglans regia L.). It occurs in Europe as well as in America, Australia and Asia. In France, this disease caused by Xanthomonas arboricola pv. juglandis is the main problem walnut growers have to deal with. When the environmental conditions are favourable to its development (soft soil, warm and wet weather) these bacteria will develop on walnuts causing husk necroses and early nut drops which can easily exceed 50% losses. Copper compounds, applied prior to rainfall events, are the traditional and only registered treatments which can be used against walnut blight in France. However, they are being used less because of their low efficacy and the environmental problems they create. A lot of different forms of copper have already been tested. However, no study has been done on chelated copper. This form of copper presents the advantage of being more easily assimilated by plants, and thus more effective. Moreover, the doses of copper used are much lower than the conventionally used copper products. Each year since 2006, we have tested Chelal^® kubig (a copper chelate produced by BMS micronutrients) against walnut blight on the same orchard of ‘Franquette’ planted in 1994. Lower walnut drops were noticed with 4 sprayings of Chelal^® kubig (done at 3 L/ha, equal to 240 g Cu/ha, between bud break to blooming) in comparison with Sulfate copper (use at 12.5 kg/ha, equal to 2.5 kg Cu/ha, with the same spray number and positioning) and a non-treated control. This difference was also reflected in yield and thus, in financial benefits.