Evaluation of innovative products to reduce copper applications to control potato late blight in organic production systems.

The main objective of this project, VETAB project, is to determine alternatives to massive copper utilization to control potato late blight (Phytophtora infestans (Mont.) de Bary) in organic systems. To reach such a target, we first performed a screening of candidate products and additives based on their efficiency in the laboratory, under controlled conditions. We evaluated a wide range of products: formulations with a low level of copper, antagonists suspensions, aminoacid extracts, plants extracts, potassium salts, sulphur formulation, organically stabilised peroxide and rhamnolipids. The product's suspensions were applied by vaporization on potato plants. Two different protocols of application were elaborated. To test the fungicide protection action, the product was applied four days before inoculation of the pathogen. To evaluate the defence stimulating effect, the product was applied several times during the plant growth before inoculation of the pathogen. The last vaporization was performed 4 days before inoculation. We also evaluated the resistance of the product to washing risk. Pathogen suspension was applied as droplets of 5 x 10(4) spo/ml on detached leaves. The leaves were then incubated (18 degrees C, RH > 90%, 6 days) in order to record symptoms development. The best results were obtained with formulations integrating reduced doses of copper and with potassium salts. In conclusion, a wide range of products and additives are proposed on the market but very few of those have a real efficiency. The performance of the most efficient products has to be confirmed in field trials.