ISSUE 8   June 28, 2007

DRIFT CONTROL ADJUVANTS, NOZZLES, AND GLYPHOSATE

Whether glyphosate is being applied in burndown applications at this time of the season or in the middle of summer, applications need to be managed to avoid drift to sensitive crops or adjacent properties. Related to this issue, weed scientists at the University of Nebraska published a research article this winter on the effect of five nozzle types and three drift-control agents on glyphosate drift. They measured the distance that glyphosate killed sorghum and the distance that injury was visible in winds that ranged from 3 to 21 mph. Spray droplets with a diameter of 150 microns or less are considered to be most prone to drift. In this study, they measured the spectrum of droplets produced by the applications to determine the droplet size where 10% of the spray was in droplets smaller than this diameter. All applications were made in 10 gpa at 40 psi.

In general, the study confirmed previous research and found the Turbo FloodJet, TeeJet AI, and Turbo Drop nozzles produced larger droplets than the Turbo TeeJet and XR TeeJet (Table 1). As a consequence, the distance that glyphosate drift caused injury was reduced 22 to 32% with these three nozzles compared with the XR TeeJet. The Turbo TeeJet nozzle also reduced the distance injury from drift was observed, but the droplet size was not statistically larger than the XR nozzle. The XR TeeJet was also tested at 20 psi and injury from drift occurred at the same distance as when 40 psi was used (data not shown). While these nozzles can affect droplet size, which is important in managing drift, it should be noted that none of these nozzles eliminated drift.

The drift agents studied were Array, an organic elasto polymer with AMS; Border EG 250, a blend of nonionic, watersoluble polymers; and Placement, a herbicide encapsulator. When evaluating the effect of drift control agents, none of these adjuvants reduced the distance glyphosate drifted with the XR TeeJet nozzle (Table 2). With the TeeJet AI nozzle, Border was the only drift control agent that reduced the distance that glyphosate injury was measured compared with no control agent. The three drift control agents increased the droplet size slightly when sprayed through the AI nozzle, but this did not always reduce the distance that drift occurred.

Table 1. Effect of nozzle type on droplet size and glyphosate drift to sorghum.

Nozzle type

10% of spray in droplets less than this diameter

Distance sorghum was:

Killed

Injured

 

microns

meters

TF-2 Turbo FloodJet

261 bc

1.1 a

5.5 a

11004 TeeJet Air Induction

284 a

1.1 a

5.7 a

TD04 TurboDrop

267 ab

1.1 a

6.3 a

11004 Turbo TeeJet

250 cd

1.3 ab

6.2 a

11004 XR TeeJet

240 de

1.6 b

8.1 b

Table 2. Effect of nozzle type and drift agent on droplet size and glyphosate drift.

Nozzle type

Drift agent

10% of the spray in droplets smaller than this diameter

was:

Killed

Injured

   

microns

meters

11004 XR TeeJet

None

240 ab

1.8 a

8.6 a

Array

256 a

1.7 a

7.7 a

Border

240 ab

1.7 a

7.2 a

Placement

232 b

1.6 a

8.2 a

11004 TeeJet AI

None

285 b

1.1 ab

6.2 b

Array

303 a

0.9 ab

5.8 b

Border

302 a

0.8 a

4.8 a

Placement

308 a

1.4 b

6.0 b

Important conclusions that the authors made from this study were 1) XR nozzles are discouraged in high wind conditions compared to the other nozzles tested; 2) a greater reduction in glyphosate drift would occur more frequently by using drift-reducing nozzles than drift control agents; and 3) drift-reducing nozzles would be less expensive than using a drift control agent in every spray application.

Based on observations, these additional comments might apply.

  • Low wind (0 to 3 mph) is unpredictable. Wind direction may shift during the time while the application is being made and blow towards a sensitive site if present.
  • A mild wind (3-8 mph) that is blowing away from a sensitive field or property may the best condition because its direction is more likely to remain consistent. (Remember, herbicides donít drift upwind. If you know the wind direction, fields up wind are safe from drifting spray droplets).
  • Despite using the best technology of drift-reducing nozzles or drift control agents, these technologies only lessen drift. They donít create a shield around the sprayer. With higher winds, when spraying near sensitive sites, or when spraying highly active herbicides or herbicides that cause highly visible injury, drift may still happen.
  • Source: Johnson, A.K., F.W. Roeth, A.R. Martin, and R.N. Klein. 2006. Glyphosate spray drift management with drift-reducing nozzles and adjuvants. Weed Technol. 20:893-897.

    Richard Zollinger
    NDSU Extension Weed Specialist
    r.zollinger@ndsu.edu


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