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Title: Foliar Deposition and Off-Target Loss with Different Spray Techniques in Nursery Application

item Zhu, Heping
item Derksen, Richard
item GULER, H - OSU
item Krause, Charles
item OZKAN, H - OSU

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2006
Publication Date: 3/15/2006
Citation: Zhu, H., Derksen, R.C., Guler, H., Krause, C.R., Ozkan, H.E. 2006. Foliar Deposition and Off-Target Loss with Different Spray Techniques in Nursery Application. Transactions of the ASAE. 49(2):325-334.

Interpretive Summary: The floral and nursery industries generally produces high-value crops with more complicated strategies of pest control material use and more intensive labor requirements than field crops. Little information is available on nursery crop production practices whereby applications of required amounts of pesticides achieve effective pest and disease control with minimum chemical loss. Due to crop similarity, air assisted application technologies for apple and citrus orchards are normally adapted to nursery tree crops. However, compared with orchard crops, nursery trees are usually narrow and sharp and are difficult to apply pesticide with conventional delivery systems. Research was conducted to compare spray deposits within nursery tree canopies and off-target loss to the ground and air from an air blast sprayer with conventional hollow cone nozzles, conventional hollow cone nozzles applying a drift retardant spray, and air induction nozzles in both a commercial nursery field and a wind tunnel. Test results indicated that the three treatments produced almost no significant differences in quantity of spray deposits within tree canopies. Tree canopies received 4 to 15 times spray as actually needed from the strategy typically recommended for nursery spray application. The spray application rate should be considerably reduced to achieve the economic and effective pesticide spray management in nursery tree production.

Technical Abstract: Information is lacking on spray techniques to improve deposit uniformity within nursery canopies and reduce off-target loss on the ground and via spray drift from the treated area. Spray deposits at various elevations within crabapple trees and on the ground were investigated with an air blast sprayer equipped with conventional hollow cone nozzles, air induction nozzles, and conventional hollow cone nozzles with a drift retardant in a commercial nursery field. Airborne deposits at three elevations on sampling towers and on the ground at several distances from the sprayer were also investigated with the three spray treatments in an open area without trees. To compare field test results, wind tunnel experiments were conducted to assess spray deposits on the floor beyond 0.4 m downwind distance from the nozzles and airborne deposits at 2.1 m downwind from the spray discharge point with the three spray techniques. Droplet size distributions across spray patterns were measured with a laser particle/droplet image analysis system. In general, there was no significant difference for deposits within nursery tree canopies and on the ground with three different spray techniques. At the 700 L/ha application rate, which was 360 L/ha lower than the rate typically used in nursery application, the tree canopies received over 4 to 14.5 times as much spray deposit as actually needed from all treatments, and a large portion of spray volume deposited on the ground. Compared with conventional hollow cone nozzles, drift reduction from air induction nozzles or the spray mixture with drift retardant treatment was significant in wind tunnel tests but was not significant in field tests.