Use of Biocontrol Agents and Plant Resistance Inducers for the control of potato late blight

Late blight ( Phytophthora infestans ) is a major disease in potato cultivation, managed primarily with synthetic fungicides. This reliance makes potatoes one of the crops with the highest fungicide load. To reduce chemical dependence and promote Integrated Pest Management (IPM), alternative solutions are needed. This study explores biological control agents (BCAs) and plant resistance inducers (PRIs) as sustainable alternatives. We screened 17 BCAs and 3 PRIs in a detached leaf assay (DLA) and selected the most effective for further trials. The chosen BCAs — Polyversum ( Pythium oligandrum ), Nvs 2 ( Bacillus amyloliquefaciens ), TC 4 ( Trichoderma atroviride ), TC 6 ( T. harzianum )—and the PRI ChiProPlant (Chitosan hydrochloride) were tested in greenhouse and field trials across five European countries. In greenhouse trials, ChiProPlant and T. atroviride significantly controlled late blight. Dosage did not affect the efficacy of the BCAs and PRI, but application timing was crucial. Treatments applied 1 and 5 days before inoculation were most effective, while post-inoculation treatments were least effective. Field trials showed that weekly applications of ChiProPlant, Polyversum, and Nvs 2 significantly reduced late blight infection. However, none matched the efficacy of synthetic fungicides. This study highlights the potential of BCAs and PRIs in late blight management but underscores the need for further research to optimize their integration into IPM strategies.