Proactive Control of Petri Disease of Grapevine Through Treatment of Propagation Material.

Petri disease is a vascular disease associated with decline and dieback of young grapevines. A major means of spread of the causal organisms, Phaeomoniella chlamydospora and Phaeoacremonium spp., is via infected propagation material. Since no curative control measures are known, proactive measures must be taken in grapevine nurseries to manage this disease. To study this aspect, semicommercial trials with naturally infected rootstock material were performed in grapevine nurseries in South Africa. Prior to grafting, rootstocks were treated as follows: 1-h drench in suspensions of benomyl, phosphoric acid, different bacterial and Trichoderma formulations, water, or hot water treated (HWT; 30 min at 50°C). Grafted cuttings were planted and grown in a greenhouse and two commercial field nurseries and uprooted 8 months later. In instances where rootstocks were treated with benomyl or Trichoderma formulations, the incidences of Phaeomoniella and Phaeoacremonium in grafted cuttings and uprooted nursery vines were significantly lower than that of the water treatment. However, the reduction was most consistent and noteworthy in vines on rootstocks that received HWT prior to grafting. HWT of dormant nursery vines effected a similar reduction in Phaeomoniella and Phaeoacremonium incidence. Root-stock drenches in benomyl and/or Trichoderma formulations could thus be integrated with HWT for the proactive management of Petri disease in grapevine nurseries.