Biocontrol Agents of Fusarium Head Blight in Wheat: A Meta-Analytic Approach to Elucidate Their Strengths and Weaknesses

The use of biocontrol agents (BCAs) coping with fungal pathogens causing Fusarium head blight (FHB) is a compelling strategy for disease management, but a better elucidation of their effectiveness is crucial. Meta-analysis is the analysis of the results of multiple studies, which is typically performed to synthesize evidence from many possible sources in a formal probabilistic manner. This meta-analytic study, including 30 pathometric, biometric, physiochemical, genetic, and mycotoxin response variables reported in 56 studies, evidences the BCA effects on FHB in wheat. The effectiveness of BCAs of FHB in wheat in terms of pathogen abundance and disease reductions, biomass and yield conservation, and mycotoxin prevention/control was confirmed. BCAs showed higher efficacy (i) in studies published more recently; (ii) under controlled conditions; (iii) in high susceptible wheat cultivars; (iv) when Fusarium inoculation and BCA treatment did not occur directly on the plant (i.e., at the seed and kernel levels) in terms of disease development and mycotoxin control, and vice versa in terms of biomass conservation; (v) if Fusarium inoculation and BCA treatment occurred by spraying spikes in terms of yield; (vi) at 15 to 21 days post Fusarium inoculation or BCA treatment; and (vii) if they were filamentous fungi. However, BCAs overall were less efficacious than conventional agrochemicals, especially in terms of pathogen abundance and FHB reductions, as well as of mycotoxin prevention/control, although inconsistencies were reported among the investigated moderator variables. This study also highlights the complexity of reaching a good balance among BCA effects, and the need for further research.