Crown and root rot caused by soilborne species of Phytophthora are common diseases of container-grown ornamental plants in nursery. Crown rot of Rose caused by P. citrophthora has been recently reported in Sicily (southern Italy). Valiphenal (IR 5885) is a systemic dipeptide fungicide of the valinamide class of compounds and is active against Oomycetes. This new fungicide is under development by the italian agrochemical company ISAGRO against powdery mildews of grapevine, potatoes and vegetables. In this study, the efficacy of Valiphenal and other experimental active ingredients was tested for the first time against crown rot of Rose. Phosetyl-Al (Aliette) was used as a reference product. Minigreffe plants of ‘Red France’ Rose on Rosa indica-major as rootstck, grown in pots (diameter 16 cm) in a plastic-house were used in all experiments. Plants were wound inoculated on the stem with agar plugs taken from P. citrophthora colonies growing on potato dextrose agar. Wounds were sealed with Parafilm and symptoms were evaluated at various time intervals after inoculation. Valiphenal, alone or mixed with biostimulants, such as the leaf organic fertilizer Siapton, was applied as foliar spray at the dose of 0.75 g/l a. i., 7 days before the inoculation. In all experiments Valiphenal proved to be as effective as Phosetyl-Al in reducing the length of the cankers on the stems of inoculated plants. Five months after the inoculation, plants treated with Valiphenal or Phosetyl-Al did not show symtoms of stem dieback whereas all nontreated control plants wilted. The addition of Siapton increased the efficacy of Valiphenal but results were not consistent among experiments. No symptoms of phytotoxicity were observed on treated plants
