Exploratory Three-Year Field Assessment of Trichoderma-Colonized Mulch for Managing Armillaria mellea in Vineyards

Sustainable management of the fungus Armillaria mellea (white root rot) in viticulture is hindered by the lack of effective chemical treatments and quantitative diagnostic tools. This study adopts a circular economy perspective by repurposing spent mushroom substrate colonized by Trichoderma, a prevalent local industrial byproduct, as an organic mulch. We hypothesized that this colonized substrate, selected for the aggressive mycoparasitic capabilities and competitive niche exclusion of Trichoderma, could mitigate pathogen expansion and support vine longevity. The objective was to evaluate the impact on pathogen expansion of this Trichoderma-colonized mulch compared to (i) an untreated control (no mulch) and (ii) an identical composted substrate without T. harzianum. Over a 3-year field assessment using a non-replicated, single-plot-per-treatment in a commercial vineyard (Vitis vinifera), the system was evaluated through longitudinal visual health monitoring, and a newly developed qPCR framework using novel species-specific primers and probe for A. mellea that was applied to a subset of the data and therefore showed limited treatment-level evidence. Initially healthy plants under Trichoderma-colonized mulch (n = 271) showed high health retention (81.2%), comparable to the untreated control (n = 320; 80.9%). This rate was significantly higher than that of the non-colonized compost mulch (n = 329; 65.0%; p < 0.001), which showed the highest disease incidence in this cohort. In initially infected vines, the survival rate was higher (but not significantly) under the biocontrol treatment (n = 50; 54.0%) than in the untreated control (n = 45; 37.8%), and significantly higher than in the non-colonized compost mulch (n = 31; 22.6%; p = 0.032). These findings constitute exploratory field evidence that Trichoderma-colonized mulch may mitigate disease progression compared with non-colonized compost mulch, particularly in already symptomatic vines, but replicated field trials are required to confirm treatment efficacy. Besides, the study provides a quantitative framework for the molecular detection and monitoring of A. mellea in woody ecosystems.