Foliar Fungicide Efficacy and Environmental Influences in Crop Disease Management

Foliar fungicides remain a cornerstone of disease management in modern crop production systems, yet their field performance can be inconsistent and difficult to predict. While fungicide efficacy is often attributed to product choice and application timing, environmental conditions may alter spray deposition, uptake, movement within plants, host physiology, and pathogen development. As agricultural systems face increasing climatic variability, understanding how environmental factors affect foliar fungicides is critical for reliable disease control and yield protection. This review examines the mechanistic basis of fungicide-plant interactions, including mode of action, uptake, redistribution, and effects on plant metabolism and defense. It also synthesizes current knowledge on how environmental stress modifies foliar fungicide performance across field crop systems, focusing on the roles of temperature, leaf wetness, rainfall, humidity, solar radiation, drought, and wind in influencing fungicide retention, absorption, redistribution, and persistence. Evidence from diverse agricultural systems demonstrates that environmental conditions can enhance or diminish fungicide effectiveness and, in some cases, mask poor fungicide performance or create the illusion of effective disease control. This review highlights practical strategies to improve fungicide reliability under challenging conditions. By clarifying how environmental factors interact with plant and fungicide biology, this review provides a foundation for interpreting field outcomes and guiding future efforts to improve fungicide reliability under variable agroecosystem conditions.