Non‑conventional treatments to control cork oak infection by Phytophthora cinnamomi

Cork oak (Quercus suber) is one of the most important forest species in Portugal and in the Mediterranean basin, but in recent decades a progressive decline has been registered in the montado ecosystem. The main phytopathogenic agent involved in this process, Phytophthora cinnamomi, has a high infection potential and survival ability, and became a serious threat to this ecosystem. Extensive areas of cork oak are infected in Portugal, being imperative to find new ways to control this disease. The complex lifecycle of this pathogen and the small number of effective agrochemicals currently authorized against Phytophthora spp., with phosphonates taking advantage, justifies this work where new products with antagonism against Oomycetes or biostimulant properties were tested. This study aimed to evaluate the efficacy of BLAD (a polypeptide with antifungal, anti-oomycete and biostimulant properties), potassium phosphonate and salicylic acid in Q. suber infected with P. cinnamomi, quantifying the severity of root lesions. BLAD, potassium phosphonate and salicylic acid treatments showed lower root lesion severities than the inoculated control, and proved to be effective as they provided a slower disease evolution. The lowest lesion severity in cork oak roots observed with BLAD treatments allowed us to consider BLAD as the most promising product among the three we tested.