Black Foot of Grapevine : Sensitivity of Cylindrocarpon destructans to Fungicides

Abstract

Black foot disease of grapevine is caused by Cylindrocarpon spp., with C. destructans being the main pathogen isolated from vine cuttings and young vineyards in Portugal. Few recommendations for black foot disease control are presently available, and they are not easy to implement within commercial nurseries. In this study, 14 fungicides were evaluated for their effect on the mycelial growth and conidium germination of four field isolates of C. destructans. Mycelial growth of the pathogen was inhibited by DMI fungicides, prochloraz (EC50 values <0.09 mg l-1) and to a lesser extent by difenoconazole (EC50 values <2.25 mg l-1), by the benzimidazole fungicide benomyl (EC50 values <0.35 mg l-1), and by the mixtures cyprodinil + fludioxonil and carbendazim + flusilazole, which gave EC50 values <0.75 mg l-1. Among these, only cyprodinil + fludioxonil (EC50 values <0.15 mg l-1), the strobilurin fungicides, azoxystrobin and trifloxystrobin (EC50 values <2.27 mg l-1) and the phenylsulphamide fungicide tolylfluanid (EC50 < 0.54 mg l-1) were effective in reducing conidium germination. Results from in vivo studies, carried out on potted grapevine plants (cultivar Castelão) showed that benomyl, tebuconazole and the mixtures carbendazim + flusilazole and cyprodinil + fludioxonil significantly (α=0.05) improved plant growth (plant height and number of roots) and decreased disease incidence compared with non-treated plants.