Quaternary ammonium compounds (QACs) have been used as disinfestants in plant production systems since the late 20th century. In studies on the control of fungal pathogens in agricultural and horticultural crop production systems, the efficacy of QAC disinfestants is variable, ranging from very high to ineffective. A systematic review and meta-analysis were performed to establish and understand how pathogen- and application-related factors influenced product efficacy. The meta-analysis was based on 124 studies involving 14 fungal plant pathogen genera, eight target materials, and four generations of QAC products that contained different mixtures of active ingredients. A significant (P < 0.0001) reduction in either disease intensity or propagule viability resulted following disinfestation using QAC products. Hedges' g standardized mean difference (g̅+) across the studies was 2.16, indicating that QACs, on average, were highly effective against fungal pathogens. Heterogeneity was significant (P < 0.0001), indicating that effect sizes (g) were not representative of a common mean effect size and supported selection of a random effects model. In all, 78.5% of the observed variance consisted of variance in true effects with a high estimate of between-study variability (τ2 = 2.15). For fungal genus, subgroup g̅+ for genera Pseudonectria and Calonectria was significantly (P < 0.0038) higher than for all other genus subgroups, except Fusarium. For target materials, subgroup g̅+ for solution, cloth, plant, and metal were significantly (P > 0.0071) higher than for inorganic material or wood. For product generation, subgroup g̅+ for fifth-generation products was significantly (P > 0.0071) higher than for fourth-, third-, and second-generation products. Dose and time accounted for only 8 and 4%, respectively, of the true variance in effect sizes in the regression model dose, time, and dose-time (P = 0.0004). Genus accounted for 40 and 51% of the true variance in effect sizes in the regression models dose and genus (P = 0.0008) and time and genus (P = 0.0007), respectively. Target material accounted for 18 and 19% of the true variance in effect sizes in the regression models dose and target (P = 0.0001) and time and target (P = 0.0001), respectively. QAC product generation accounted for 24 and 21% of the true variance in effect sizes in the regression models dose and QAC generation (P = 0.0034) and time and QAC generation (P = 0.0189), respectively. These results show that the current recommended rates for dose and contact time are generally expected to result in effective disinfestation for commercial QAC products. However, the efficacy against fungal plant pathogens is likely to be influenced by the fungal genus and target being treated and the generation of the QAC product that is used for disinfestation.
Keywords: QAC; disinfectant; fungi; plant pathogen; quats; sanitizer.