Selected foliar fertilization in a strategy for the reduction of esca foliar symptoms. In "Abstracts of oral and poster presentations given at the 8th International Workshop on Grapevine Trunk Diseases, Valencia, Spain, 18–21 June 2012"

Results obtained in previous investigations have stimulatedthese trials that evaluate a commercial foliar fertilizerbased on calcium and magnesium, plus adjuvantsthat facilitate their penetration, bioavailability and distributionin the plant. In 2010, nine treatments wereperformed between the phenological stages “third leafunfolded” and “bunch closing”. A consistent decreasein the expression of foliar esca symptoms was observed,and an increase of trans-resveratrol content in the leavesoccurred after the first four treatments. In 2011, in orderto investigate the most active components in the fertilizer,the treatments were repeated by separately applyingcalcium, magnesium or a tank mixture of both. Thetrial was extended to two other additional vineyards.The commercial fertilizer confirmed the decrease of foliarsymptoms and the increase of trans-resveratrol in theleaves. The application of the mixture calcium + magnesiumor calcium or magnesium separately also showeda reduction of symptoms, although to a lesser extentthan that of the commercial preparation. This modularityof effects, would suggest an activity of calcium andmagnesium in the manifestation of symptoms, even inthe absence of adjuvants, and that the physiology of theplant may play a role in foliar expression. Numerous reportson the effect of calcium on various plant diseasesare present in the literature. Less known is the activityof magnesium, which has shown contradictory effectswhen investigated in different pathosystems. Furtherstudies on the mechanisms of action are in progress.[...]