Effects of fosetyl Al treatments on grapevine plants in esca management

Esca is the most severe and widespread grapevine wood disease. Although foliar symptom expression is not correlated with vine wood deterioration because of the intermittent nature of esca leaf symptom, the loss of production is associated with foliar symptom expression being diseased asymptomatic vines able to produce grapes with similar characteristics to grapes from healthy vines. Foliar symptoms seem to be associated with transport of toxins from infected wood to leaves. A reduction in esca symptom severity was observed in many-year trials applying commercial formulations of fosetyl Al either before or soon after the appearance of esca in vineyards properly managed and following the plan for downy mildew control. Moreover, a reduction of the average length of internal necrosis following inoculations with vascular esca pathogens and treated by fosetyl Al was noticed in potted vines. Investigations were carried out in order to explain the activity of fosetyl Al towards esca and associated pathogens. Physiological parameters of potted plants were measured: net photosynthetic rates of infected untreated plants were depressed by 20-50% for 24-60 hours after treatment compared to infected untreated ones. Foliar total proteins were extracted and tested by spectrophotometric analyses. In infected treated leaves chitobiosidase and glucosaminidase activities increased from 3 to 9 days after treatment, glucanase activity was enhanced at the third day and lypoxigenase activity increased over the time at pH 6.5, compared to untreated leaves. No differences in trans-resveratrol and ε-viniferin contents were found in the wood of treated and untreated vines. Results were discussed.