Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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APPLICATOR EXPOSURE AND DRIFT OF LAWN CHEMICALS WITH A WET BLADE
MOWER AND THREE FOLIAR SPRAY METHODS. S.D. Askew, Virginia Tech,
Blacksburg.
ABSTRACT
In the home lawn environment, applicators, residents, and surrounding vegetation
are all at risk of pesticide exposure. Herbicides such as 2,4-D have been shown to
dislodge from treated lawns and be deposited inside the home on various surfaces.
Thus, limiting applicator exposure, reentry exposure, and drift are all valuable attributes to
any application method. The wet blade mower delivers chemicals and nutrients to plants
by wiping liquid product onto the cut plant surface. This liquid delivery method has
several potential benefits compared to conventional spray techniques. Our objective was
to evaluate applicator exposure, reentry exposure, and drift of liquids applied with the wet
blade mower (WB), a rear-mounted boom-type sprayer (BS), a backpack sprayer with
hand wand (BP), and a commercial “spray gun” type sprayer (SG).
A spray pattern indicator, Brazon (1% solution), was used in this study. Mixed tall
fescue and Kentucky bluegrass turf maintained at 2.5 inch were divided into 500 ft 2 plots.
These plots were treated with 2.5 gal of Brazon/A at a delivery rate of 43.6 gal/A for foliar
spray methods and 2.5 gal/A for the WB. Filter papers were placed at regular intervals
leading away from the sprayer’s first pass in each plot. A wind source was positioned to
supply a sustained wind speed of 5 to 7 mph. The first pass of the applicator was upwind
of the evenly spaced filter papers; papers were immediately collected after the applicator
passed. Filter papers were affixed to the applicator’s spray suit to test exposure at
different areas on the body. These papers were collected after each treated plot and
analyzed. In addition, papers were affixed to the bottom, front, and top of the right shoe
and plots were traversed twice at 10 min and 24 hr after treatment. Each of the four
application methods were replicated three times in a RCB and the study was conducted
on October 27, 2005, October 3 and 4, 2006 at three different sites.
Substantial drift occurred from all foliar spray application methods but not from the
WB. When actual dye values were converted, the foliar spray application methods
deposited 77 to 86% of a full rate on bare ground while the WB deposited 22% of a full
rate to bare ground. Thus, the WB does not apply as much chemical to areas that are
void of vegetation. The small amount of chemical deposited by the mower is attributed to
“shatter” effect as the wet undersurface of the mower blade contacts grass leaf blades at
high velocity and propels small droplets onto neighboring areas under the mower deck.
As much as 58 to 81% of a full application rate was extracted from the shoe front 10 min
after treatment with foliar spray methods and 35% was extracted 10 min after WB
application. After 24 hr, all application methods resulted in 2 to 7% of the full rate
dislodged by filter paper and were statistically equivalent. WB and rear boom application
methods did not expose the applicator to any chemical while SG and pump sprayer
methods exposed the worker to between 6.1 and 8.9 μl of dye. In some locations on the
body (e.g., shoes), the applicator was exposed to nearly a full chemical rate. The WB
method reduced drift, applicator and early reentry exposure to chemical dye in all studies.
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