Experiments on the control of esca by Trichoderma

Trichoderma harzianum T39 (Trichodex®) and T. longibrachiatum strain 6 were applied on grapevine to determine their effectiveness against Phaeomoniella chlamydospora on vine cuttings and pruning wounds. Cuttings were dipped in a Trichoderma suspension either before or after callusing. Pre-callusing dips were carried out for 3 years and yielded contradictory results. By contrast, post-callusing Trichoderma dips led to significant growth of hairy roots and a reduction in the longitudinal discolorations caused by P. chlamydospora inoculated into the rootstock after dipping. Trichoderma spp. were also applied to pruning wounds of grafted potted vines, which were then inoculated by placing drops of a conidial suspension of P. chlamydospora on the wound surface. Trichoderma application here prevented black goo and necrosis in the wood below the wound. In the vineyard, T. harzianum T39 was sprayed after pruning for two consecutive years. The biocontrol agent was reisolated from the wood close to the sprayed pruning wounds for up to 2 months after spraying. Although further investigations are necessary, our findings suggest that Trichoderma could be one of the steps in the control of esca.