AN HYPOTHESIS OF SYSTEMIC ACQUIRED RESISTANCE INDUCED BY FOLIAR NUTRITION: EFFECTS OF "PS01KD" (VALAGRO^® PROTOTYPE) TREATMENT IN GRAPEVINES (VITIS VINIFERA)

PS01KD is a Valagro^® prototype, based on specific components and organic classes of molecules. Those have shown to increase the plant capability to resist against pathogens through induction of mechanisms for Local or Systemic Acquired Resistance. The efficacy and crop safety of PS01KD when used to control downy mildew (Plasmopara viticola) in inoculated grapevine (Vitis vinifera cv Chardonnay) was evaluated. The prototype and the fungicides were applied to shoots of mature grapevines. PS01KD was compared with phosphonic acid 20% w/v (Foli-R-Fos) and metalaxil 25% w/w (Ridomil). Those were applied 4 days later inoculation to test curative activity of applications; 14 days after inoculation to test if post-symptom application inhibited sporulation of downy mildew; 14 days and 7 days before inoculation to verify the prototype efficacy by spraying either before or after inoculation. The experiments showed that PS01KD was effectively able to stimulate resistance mechanisms with the viable result to reduce drastically the percentage of leaves infected per shoot (even to zero for some applications). As expected, post-symptom applications did not inhibit sporulation.