Use of Tartrazine Dye to Measure Foliar Spray Deposition on Turfgrass.

Effective foliar applications can save labor, money, and increase control levels. The efficiency of an application is typically evaluated by the biological response; however, other factors, such as retention of the spray solution by the foliage, may influence control levels.This research was conducted to determine the retention of spray application by turfgrass foliage. Turfgrass species tested included creeping bentgrass (Agrostis stolonifera L.) and Kentucky bluegrass (Poa pratensis L.). Tartrazine was used as a tracer to evaluate the effects of spray volume, nozzle types, leaf area index, adjuvants, mowing heights, and presence of dew on the quantity of spray solution retained on the foliage. The ratio of the solution retained on the leaf to the amount of solution sprayed (recovery rate) and the amount of solution retained on leaf (retention volume) were utilized to assess efficiency. Increasing spray volume from 66 L ha^-1 to 840 L ha^-1 decreased the recovery rate from 100.7% to 61.1%. However, the recovery rate remained stable near 60% as the spray volume increased from 840 L ha^-1 to 1550 L ha^-1. A linear relationship (R²=0.9965) was observed between retention volume and spray volume. Additional results will be presented.