Effects of biostimulants on esca

Biostimulants are compounds that influence plant physiological processes producing faster growing and healthier plants and enhanced stress tolerance. The esca complex is correlated with host-plant physiology and can be also considered a stress-related disease. Efficient control methods in the vineyard are most lacking, especially increasing age of plant and incidence of the disease. The activity of some biostimulants was investigated in many-year trials in order to assess effects on both the incidence and severity of leaf symptoms in the vineyard and the development of Phaeomoniella chlamydospora artificially inoculated in potted vines. Field trials were carried out in 5 15-20-year-old vineyards for 4-7 consecutive years. Three-four treatments for each biostimulants were set up based on the Companies indications. Potted plants were treated, trunk inoculated with P. chlamydospora, and treated for the 2 following consecutive years. In field trials, treatments did not provide a reduction of foliar symptoms; in some cases the annual and cumulated incidence increased. Treated vines that showed foliar symptoms in a certain year of investigation will have showed foliar symptoms during the following years more frequently compared to untreated vines. On the other hand the percentage of mortality decreased in treated vineyards. After 3 years of treatmens, two of the tested biostimulants reduced the development of the internal necrosis caused by P. chlamydospora. The percentage of fungal re-isolation from infected treated vines was generally lower than untreated ones. Prospects for biostimulants as a means to be considered in esca control strategies are discussed.