A Systematic Review and Quantitative Synthesis of the Efficacy of Quaternary Ammonium Compounds Disinfectants Against Fungal Plant Pathogens

Authors: Copes, Warren; OJIAMBO, PETER - North Carolina State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2022
Publication Date: 2/1/2023
Citation: Copes, W.E., Ojiambo, P. 2023. A Systematic Review and Quantitative Synthesis of the Efficacy of Quaternary Ammonium Compounds Disinfectants Against Fungal Plant Pathogens. Plant Disease. 107(2):480-492. https://doi.org/10.1094/PDIS-09-21-2018-RE.
DOI: https://doi.org/10.1094/PDIS-09-21-2018-RE

Interpretive Summary: Quaternary ammonium compounds (QACs) are disinfestants used to treat and eliminate fungal plant pathogens present on surfaces of tools and equipment and in large production areas in plant production systems. While these products are generally effective, too few studies are available to fully understand how consistent these disinfestants are at achieving these goals. Meta-analysis provides a way to evaluate the efficacy of QAC products across a population of studies and determine if conclusions can be drawn on application-orientated factors when treating a broad range of plant pathogens. QAC products were generally effective when treating non-porous surfaces, such as metal and wood. On non-porous surfaces, QAC products were effective for treating cloth and Styrofoam surfaces, but were generally ineffective when treating wood surfaces. Most fungal genera were controlled with QACs, but control was not equal for all fungal genera. The QAC generation was a third factor shown to influence product efficacy. The trend was later generations, such as 5th generation products, provided increasing and more consistent control against fungal plant pathogens than earlier generations, such as 2nd generation products. This information will be useful to people working in agricultural and horticultural plant production for selecting QAC products that effectively control plant pathogens contaminating tools, equipment and production areas.

Technical Abstract: Quaternary ammonium compounds (QACs) have been used as disinfestants in plant production systems since the later-twentieth 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 irrespective of the dose and contact time of application. A systematic review and meta-analysis were performed to establish and understand how pathogen and application related factors influenced product efficacy. The meta-analysis comprised 124 studies involving fourteen fungal plant pathogen genera, eight target materials and four generations of QAC products that contained different mixtures of active ingredients. QACs caused a significant (P < 0.0001) reduction in either disease intensity or propagule viability with a mean Hedges’ g standardized mean difference ('G') of 2.09, indicating QACs were highly effective on average. Heterogeneity was significant (P < 0.0001) indicating effect sizes (g) were not representative of a common mean effect size and supported selection of a random effects (RE) model. A 73.8% of the observed variance consisted of variance in true effects with a high estimate of between-study variability (Tau-sq = 1.99). For fungal genus, subgroup 'G' for Pseudonectria and Calonectria were significantly (P < 0.0071) higher than for all other genus subgroups, except Fusarium. For target materials, subgroup 'G' for solution, 'Other' (plant, Styrofoam), cloth and metal materials were significantly (P > 0.0071) higher than inorganic and wood materials. For QAC product generations, subgroup 'G' for 5th generation products was significantly (P > 0.0071) higher than for 4th, 3rd and 2nd generation products. Dose and time, respectively, accounted for 8% and 4% of the true variance in effect sizes in the regression model dose, time and dose × time (P = 0.0011). Genus accounted for 67% and 59% of the true variance in effect sizes, respectively, in the regression models dose, genus and dose × genus (P = 0.0001) and time and genus (P = 0.0001). Target material accounted for 26% and 24% of the true variance in effect sizes, respectively, in the regression models dose and target (P = 0.0001) and time, target and time × target (P = 0.0001). These results show the current recommended rates for dose and contact time are generally expected to result in effective disinfestation for commercial QAC products but the efficacy against fungal plant pathogens is expected to be influenced by the fungal genus and target being treated with QAC, and by what generation QAC product is applied.