Evaluation of fungicides to control Cylindrocarpon liriodendri and Cylindrocarpon macrodidymum in vitro, and their effect during the rooting phase in the grapevine propagation process

The efficacy of 14 selected fungicides against Cylindrocarpon liriodendri and Cylindrocarpon macrodidymum was evaluated in vitro by testing their effect on mycelial growth and conidial germination. Carbendazim, hydroxyquinoline sulphate, imazalil, and prochloraz were the most effective fungicides in reducing mycelial growth in both Cylindrocarpon species. Captan, copper oxicloride, didecyldimethylammonium chloride and thiram were the most effective to inhibit conidial germination of both species. A pot assay was also conducted with captan, carbendazim, copper oxychloride, didecyldimethylammonium chloride, hydroxyquinoline sulphate, imazalil and prochloraz in order to determine their potential to prevent infections caused by C. liriodendri and C. macrodidymum during the rooting phase in the grapevine propagation process. All fungicides significantly decreased the root disease severity values in both species compared with control treatment, with the exception of imazalil in C. macrodidymum. In the case of the percentage of reisolation, all values were lower than those obtained for the control treatment, but only captan, carbendazim and didecyldimethylammonium chloride were significantly different in the case of the cuttings inoculated with C. liriodendri, and prochloraz in the case of those inoculated with C. macrodidymum.

Research highlights
► The efficacy of 14 selected fungicides against Cylindrocarpon liriodendri and C. macrodidymum was evaluated in vitro by means of mycelial growth and conidial germination assays.
► Carbendazim, hydroxyquinoline sulphate, imazalil and prochloraz were the most effective fungicides to reduce mycelial growth in both Cylindrocarpon species, while captan, copper oxychloride, didecyldimethylammonium chloride and thiram were the most effective to inhibit conidial germination.
► An assay was also conducted with captan, carbendazim, copper oxychloride, didecyldimethylammonium chloride, hydroxyquinoline sulphate, imazalil and prochloraz in order to determine their potential to prevent infections caused by C. liriodendri and C. macrodidymum during the rooting phase in the grapevine propagation process.
► All fungicides significantly decreased the root disease severity values in both species compared with control treatment, with the exception of imazalil in C. macrodidymum. Moreover, the percentages of reisolation of both pathogens from infected roots were lower than those obtained for the control treatment, although mostly not significantly different.