Action of fosetyl and metalaxyl against Phytophthora austrocedri

SILVA, P.V.; VÉLEZ M.L.; HERNÁNDEZ OTAÑO, D.; NUÑEZ, C.; GRESLEBIN, A.G.

FOREST PATHOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 46 p. 54 - 66

1437-4781

Fosetyl-Al and metalaxyl, the most commonly used systemic fungicides against Phytophthora, were evaluated for their efficacy to controlPhytophthora austrocedri, the pathogen that causes a serious disease at the Austrocedrus chilensis forests in Patagonia. The effect of thechemicals on pathogen development in vitro and in planta was analysed. Both chemicals were shown to protect plants from the pathogen.In vitro assays showed that asexual reproduction was sensitive to both chemicals. However, mycelial growth and sexual reproduction,which were clearly sensitive to metalaxyl, were sensitive only to high concentrations of fosetyl-Al. Fosetyl-Al and metalaxyl had almost thesame efficacy when applied preventively by soil drench to seedlings. This difference between in vitro and in planta results can be attributedto the dual action of fosetyl-Al, not only inhibiting the pathogen but also stimulating host defence. In adult trees, preventive and curativetreatments were tested, but only the fosetyl-Al preventive treatment was effective in the assayed conditions. Interestingly, seedlingspretreated with both fungicides were less susceptible to the effectors secreted by the pathogen. Our results indicate that fosetyl-Al andmetalaxyl provide some resistance to the plant besides the fungistatic direct action on the pathogen. Further studies to elucidate a possibleresistance-inducing activity of these chemicals and the mechanisms involved are underway.