Wind tunnel studies on spray deposition on leaves of tree species used for windbreaks and exposure of honey bees

Abstract

A wind tunnel study was conducted to determine pesticide deposition on commonly used windbreak tree species used as spray drift barriers and associated exposure of honey bees. Although it has been known that windbreaks are effective in reducing chemical drift from agricultural applications, there is still an enormous information and data gap on details of the dependence of the mechanism on the biological materials of the barriers and on standardization of relevant assessment methods. Beneficial arthropods like honey bees are adversely affected by airborne drift of pesticides. A study was initiated by first establishing a wind tunnel to create a controlled environment for capture efficiency work. Suitable spray parameters were determined after a preliminary study to construct and develop a wind tunnel protocol. A tracer dye solution was sprayed onto the windbreak samples and honey bees located in the wind tunnel at various simulated wind speeds. Analysis of data from this work has shown that needle-like foliage of windbreak trees captures two to four times more spray than broad-leaves. In addition, it was determined that, at lower wind speeds, flying bees tend to capture slightly more spray than bees at rest.

Modelling the size-dependent collection efficiency of hedgerows for ambient aerosols

“…Stands of vegetation over 1 m high have been shown to be efficient pollen collectors (Treu & Emberlin, 2000). In addition, experimental evidence of drift filtration of pesticides sprayed either under field conditions (Davis, Brown, Frost, Yates, & Plant, 1994;Miller, Lane, Walklate, & Richardson, 2000) or in a wind tunnel (Ucar, Hall, Tew, & Hacker, 2003) indicate that hedge barriers can reduce drift by up to 90%.…”

Pesticide drift deposition in hedgerows from multiple spray swaths

“…However, the relation between deposition per curler and deposition per leaf area differed between hedgerows and between days, probably reflecting variation in factors such as leaf development and size, hedgerow porosity and weather conditions. 25,26) However, we have no indications of how collecting efficiency of the curlers depends on meteorological and technical factors.…”

Interaction between pesticides and other factors in effects on bees

“…The wind tunnel studies ensured bees were present in the direct spray from the application (76 mg on a target of 5625 cm 2; 13.5 µg/cm 2 ) and showed that at low wind speed deposits on flying bees were 4.6 ± 1.9 µg/bee and on dead bees 4.1 ± 0.9 µg/bee and at higher wind speeds 8.0 ± 2.1 µg/bee on flying bees and 7.9 ± 0.5 µg/bee on dead bees (Ucar et al, 2003). Given the application was only to the upper surface of the dead bees the surface area of a honeybee is 0.93 cm 2 (Johansen et al, 1983) this suggests that the maximum residue equated to 63% efficiency.…”

“…The European food Safety Authority reserves its rights, view and position as regards the issues addressed and the conclusions reached in the present document, without prejudice to the rights of the authors. Flying bees 1.5 m/s 4.6 ± 1.9 μg/bee -46000 μg /kg 2.5 m/s 6.6 ± 2.2 μg./bee -66000 μg/kg 3.5 m/s 8.0 ± 2.1 μg/bee -80000 μg/kg Dead bees 1.5 m/s 4.1 ± 0.9 μg/bee -41000 μg/kg 2.5 m/s 6.7 ± 0.2 μg./bee -67000 μg/kg 3.5 m/s 7.9 ± 0.5 μg/bee -79000 μg/kg (Ucar et al, 2003) The present document has been produced and adopted by the bodies identified above as author. This task has been carried out exclusively by the author in the context of a contract between the European Food Safety Authority and the author awarded following a tender procedure.…”

“…Studies have been undertaken in which bees were allowed to fly during tracer applications to apple trees and Phacelia ( (Koch and Weisser, 1997) and in wind tunnel experiments with both dead and tethered flying bees (Ucar et al, 2003). Initial deposits measured on dead bees in laboratory studies has shown that the residue is not affected by the volume of the application but by the product rate per hectare (Koch and Spieles, 1993).…”