Mode of colonization of Trichoderma formulated in an antifungal product (Remedier®) for pruning wound protection against infection by wood pathogens

Pruning wounds are considered the main entry sites for the wood pathogens associated with grapevine leaf stripe disease (GLSD), a disease within the esca complex, and wounds remain susceptible to infection for several weeks. Remedier® is a microbiological product containing Trichoderma gamsii and Trichoderma asperellum. The individual Trichoderma species and Remedier® were separately applied on the surfaces of grapevine shoot portions placed in sterile sand and maintained at 5, 10 or 20°C. The development of Trichoderma on the wood surfaces was evaluated by image analysis and re-isolation on PDA plates. In vineyard evaluation, two protocols were followed: (i) Remedier® was sprayed in January, February and March on freshly pruned wounds which were later inoculated with Phaeomoniella chlamydospora (Pch), the main pathogen associated with GLSD; and (ii) grapevines were pruned in January and treated with Remedier® in March. All reisolations of Trichoderma were carried out after harvest. Under laboratory conditions, T. gamsii grew on the shoot surfaces even at 5°C, 15 days after treatment. In the vineyard, re-isolation of Trichoderma species and the rate of protection against Pch was greater when Remedier® was sprayed in March. The percentages of isolation of the two species were almost equal if the treatment was applied at low average temperatures (January), while T. asperellum was re-isolated more frequently when the product was applied at increasing average temperatures (February and even more March). Remedier® showed long persistence on wound surfaces and gave the best preventive protection against Pch if sprayed in March.