Twenty Years of Fungicide Research for Laurel Wilt Management: A Systematic Review and Quantitative Synthesis

Laurel wilt, caused by Harringtonia lauricola , is a destructive vascular disease of avocado and other members of the Lauraceae. Since the pathogen was first described, researchers have evaluated numerous fungicides, formulations, and delivery methods for disease management; however, no comprehensive synthesis of this work has been conducted. This study summarizes nearly two decades of fungicide research for laurel wilt management across laboratory, greenhouse, and field settings and complements this synthesis with a field evaluation of flutriafol mobility in mature avocado trees. Published studies were compiled and compared based on fungicide activity, fungicidal thresholds, application methods, residue accumulation, and field performance. Collectively, at least 70 active ingredients representing 18 Fungicide Resistance Action Committee (FRAC) groups have been evaluated against H. lauricola . Demethylation inhibitor (DMI; FRAC 3) fungicides consistently exhibited strong in vitro activity and often prevented disease development in greenhouse-grown avocado trees. However, successful disease suppression in mature trees under field conditions was far less consistent. To further evaluate this limitation, we conducted a field trial with flutriafol, a DMI fungicide. Soil drench applications resulted in limited uptake, whereas trunk microinjections produced highly variable fungicide distribution within and among trees. Together, the review and field study indicate that the primary challenge to fungicide-based management of laurel wilt is not identifying fungitoxic compounds but achieving uniform distribution and persistence of fungicidal concentrations throughout mature trees. Future advances will likely depend on fungicides with lower fungicidal thresholds, improved formulations, and more effective delivery technologies.