Pesticide Spraying in Indian River Grapefruit: II. Overview of Factors Influencing Spray Efficacy and Off-target Deposition

Foliar application of spray materials is an integral component of commercial citrus production. An intensive assessment of spray application practices has been stimulated by low fruit value and increased concern about potential surface water contamination in the Indian River citrus region of Florida. Many publications report research results regarding distribution of spray materials within orchards and off-target deposition, but interpretation is challenging because so many factors influence spray results, and integrating this information into practical recommendations is difficult. Canopy geometry and density are prominent factors contributing to variable deposition and spray drift. Environmental factors such as temperature, relative humidity, wind speed, and wind direction also greatly influence spray deposition and drift, and substantial changes can occur within seconds. In addition the physical and/or mechanical set up of the sprayer interact significantly with the other factors. A better understanding of these interactions should help growers optimize spray effectiveness and efficiency while reducing potential off-target effects.