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There are not studies regarding risk assessment of pesticides in citrus grown in Spain. The aim of this study was to estimate the risks caused by worst-case drift scenarios from the principal pesticides used in this crop, in order to assess possible damage to the environment and human health. A field survey was performed to characterize the particular conditions of plant protection product applications to citrus in Spain. Six targets were identified to be the most affected by droplet spray drift in ours, and extensively in most Mediterranean conditions: water organisms, earthworms, bees, adult bystanders, child bystanders and residents. Three drift estimation models were used to assess the amount of drift at specific distances downwind of a field in order to calculate Risk Indicators. These showed safe conditions for earthworms and residents, but also indicated that some pesticides may pose risk to aquatic organisms, even with a 20 m buffer zone, bees, adult bystanders and child bystanders. In general, results generated similar consequences of hazard risk independently of the drift prediction model used, pointing out that toxicological data were more relevant for deducting the risks.

Atmospheric drift of plant protection products is considered a major source of air pollution during pesticide applications. Citrus protection against pests and diseases usually requires application of these products using air-blast sprayers. Many authors have emphasized the influence of vegetation on the risk of spray drift. The aim of this work was to describe in detail how the airflow from an air-blast sprayer behaves when it reaches citrus trees and, in particular, the effect that the tree canopy has on this flow. Tests were conducted at a commercial citrus orchard with conventional machinery, placed parallel to a row of trees. Air velocity and direction was measured using a 3D ultrasonic anemometer in 225 points situated in three parallel planes perpendicular to the equipment. The stability of the airflow at each measuring point was studied and the mean velocities were graphically represented. Two vortexes, one behind the canopy, and another over the tree, have been deducted and never been reported before. Both may have an important influence on the trajectories of the sprayed droplets and, as a consequence, on the way in which plant protection products are diffused into the atmosphere. Observed turbulence intensities were higher than in similar experiments conducted in other tree crops, which may be attributable to the higher air volume generated by the machinery used for citrus protection and to the higher foliage density of citrus orchards.