Drift assessment during chemical weed control

Six different sprayer models proposed on the Italian market to apply herbicides under the rows of vineyards were compared to evaluate: 1) the potential drift generated by the sprayer under controlled wind conditions; 2) their biological efficacy. Different configurations of the spraying equipment were tested: conventional and air induction nozzles (015 and 03 size); several heights and inclinations of the boom to control also the suckers. Drift tests were performed under a plastic tunnel where an even artificial air stream was generated. Two air velocities were examined: 3 m/s and 5 m/s. Field tests were made using the equipment configured to spray weeds and suckers at the same time and were carried out in an espalier Guyot trained vineyard where there was a consistent presence of weeds under the rows and of suckers around the plants. A contact herbicide was applied. Drift tests pointed out that the conventional not shielded boom sprayer equipped with normal flat fan nozzles was more susceptible to drift. When air induction nozzles were used, a consistent reduction of drift (over 50%) was obtained. The use of partly shielded equipment did not allow preventing drift as the totally shielded equipment. When the boom was inclined in order to obtain a spray jet hitting also the suckers, higher values of drift were registered either for the conventional uncovered boom (up to 44% of the applied), or for the shielded boom, while drift remained close to zero using the stepping over shielded equipment. Weed control registered in the field was pretty the same for all the sprayers compared. The conventional boom sprayers, either shielded or not, were able to kill 60% of the vine suckers while the use of the stepping over shielded equipment enabled to reach 88% of suckers killed when air induction nozzles were used.