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Title: Coverage and Drift Produced by Air Induction and Conventional Hydraulic Nozzles Used for Orchard Applications

item Derksen, Richard
item Zhu, Heping
item Fox, Robert
item Brazee, Ross
item Krause, Charles

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2007
Publication Date: 12/15/2007
Citation: Derksen, R.C., Zhu, H., Fox, R.D., Brazee, R.D., Krause, C.R. 2007. Coverage and Drift Produced by Air Induction and Conventional Hydraulic Nozzles Used for Orchard Applications. Transactions of the ASABE. 50(5):1493-1501.

Interpretive Summary: Tree fruit crops are particularly difficult crops to protect with pesticides because they are typically taller than most conventional application equipment. This requires spray to be released up into the air which increases the risk of spray moving off-target. Large droplet applications can reduce off-target spray movement but they have not been used in tree fruit applications. A field trial was established to determine the fate of spray released from a low-drift, air induction nozzle set (TD-02) and conventional, hollow cone nozzles (D3-25 and D4-25) which produce a larger driftable volume. Fluorescent tracers were used to assess spray deposits and foliar coverage in the mature apple canopies and downwind ground and airborne losses. The conventional, hollow nozzles produced higher coverage on leaf surfaces. There were no differences in the amount of spray residue found on leaves treated with either type of nozzle at 2 and 3 m sampling points above the ground. Ground losses 4 to 64 m downwind from the edge of the orchard were lower for the TD-02 nozzle compared to the D4-25 nozzle. Airborne losses were greater for the D4-25 nozzle compared to the TD-02 nozzle. Losses to the ground and air were similar for both types of nozzles from 128 to 256 m downwind from the edge of the orchard. These results demonstrate that producers using conventional, axial-flow, orchard sprayer have another option for mitigating drift but the ultimate choice of nozzle must also consider the coverage needs of their pest management materials.

Technical Abstract: The risk of environmental contamination due to pesticide sprays increases as droplet size decreases and the release height increases. Delivery of pesticides is typically made using relatively small droplets that conventional sprayers release high above the ground so that tops of trees can be treated. Field experiments were conducted in a semi-dwarf apple orchard to establish the fate of spray from traditional hollow cone nozzles (D3-25 and D4-25) and a set of drift reduction, air induction nozzles (TD-02). Fluorescent tracers were applied with all treatments to aid in assessing spray retention and coverage in the canopy and off-target, ground sedimentation and airborne spray losses. The small droplet spectrum D3-25 nozzle set produced the highest spray coverage on upperside and underside leaf surfaces at 2.0 and 3.0 m heights in the trees. Spray retention in the canopy was similar for the D4-25 and larger droplet spectrum TD-02 nozzle sets. The low-drift, TD-02 nozzle produced the lowest downwind spray losses to the ground 4-64 m beyond the edge of the orchard. Ground and airborne losses were similar for the D4-25 and TD-02 nozzles were similar at 128 and 256 m downwind from the edge of the orchard. These results demonstrate that air induction nozzles may be effective drift mitigation technologies for orchard applications; however, care must be taken to ensure that coverage requirements for maximum pesticide efficacy are met.