Ground Cover Supplement : GC Supplement - Spray application technology
GROUND COVER SPRAY APPLICATION TECHNOLOGY 10 DRIFT-REDUCTION TECHNOLOGY Coarse droplets conquer grass weeds By Jason Sabeeney pressure, coverage of target weeds was achieved with coarser droplets (Figure 1). In some situations, the use of some nozzles that produce very or extremely coarse droplets resulted in a reduction in herbicide efficacy. Results from several field trials indicate that the efficacy of Spray Seed® or Axial® herbicides was not compromised on annual ryegrass or cultivated oats when applied with a coarse spray from several nozzles including TeeJet® AI and TeeJet® AIXR. It is important to ensure that these nozzles are operated at correct operating pressures and water volumes are increased in order to maintain adequate coverage of the target weeds. A guide to pressure and water volume by nozzle type is as follows. nhigh-pressure, air-induced nozzles (for example TeeJet® AI, Hardi INJET, agrotop TurboDrop®, Lechler ID) -- apply at high pressures greater than four bar, generally four to eight bar should be used; and nlow-pressure, air-induced nozzles (for example TeeJet® AIXR, Hardi MiniDrift, agrotop, AirMix®, Lechler IDK) -- apply at pressures greater than two bar, generally three to six bar should be used. A water volume of more than 75 litres a hectare is to be used for both high and low-pressure air- induction nozzles if targeting grass weeds. The efficacy of Spray Seed® or Axial® may be compromised if water volumes are not sufficient and/or if droplet size is increased beyond a coarse spray quality. □ More information: Jason Sabeeney, Syngenta Crop Protection, 02 8876 8444, email@example.com FIGURE 1 SPRAY SEED® EFFICACY ON ANNUAL RYEGRASS 28 DAYS AFTER APPLICATION, WA 2006 INJ 01 @ 8 bar 50/C TT 015 @ 4 bar 50/M TT 02 @ 4 bar 75/M TT 03 @ 3.5 bar 100/M XR 03 @ 3.5 bar 100/F XR 015 @ 4 bar 50/F XR 02 @ 4 bar 75/F AI 015 @ 8 bar 75/C AI 02 @ 8 bar 100/C % control 0 20 40 60 100 809193 95 96 93 91 98 99 88 Nozzles: INJ = Hardi INJET TT = Turbo TeeJet® XR = TeeJet® XR AI = TeeJet® AI Nozzle flow: 01--03 Spray volumes: 50 = 50L/ha 75 = 75L/ha 100 = 100L/ha Spray quality: F=fine M = medium C = coarse TABLE 1 NOZZLES, DROPLET CLASSIFICATION AND WATER RATES USED, 2006 AND 2007 DROPLET CLASSIFICATION YEAR AND WATER VOLUMES 2006 50, 75 and 100L/ha 2007 40 and 80L/ha Fine TeeJet® XR TeeJet® XR Medium Turbo TeeJet® TeeJet® DG Coarse/medium Turbo TeeJet® Coarse TeeJet® AI Turbo TwinJet®, AIXR, Hardi MD Coarse/very coarse TeeJet® AI Extremely coarse TeeJet® TTI XR = extended range, DG = drift guard, AI = air induction, TTI = Turbo TeeJet® Induction, MD = MiniDrift Coarse droplets, less drift Coarse droplets reduce the risk of drift. Now, Australian trial data indicates that coarse droplets achieve adequate weed kill with contact herbicides RESEARCH HAS SHOWN that air-induction nozzles can provide good levels of weed control when targeting certain weeds with systemic herbicides. This trial assessed their performance under the more challenging scenario of using contact herbicides on small Lolium rigidum (annual ryegrass) or Avena spp. (cultivated oats) plants. Trials were run in 2006 in Western Australia and South Australia and, in 2007 in SA and Victoria. In both years the herbicides paraquat with diquat (Spray Seed®, Group L) and pinoxaden (Axial®, Group A), plus an adjuvant, were applied using a range of nozzles and water rates to produce spray qualities from fine to extremely coarse (Table 1). Herbicide rates were chosen to achieve 80 to 90 per cent weed control so the difference between treatments would be more evident. Application conditions at each site were appropriate and weed size ranged from two leaf to early tillering. The trials found that, providing water rates were maintained and nozzles were operated at the correct PHOTO: CPAS Coarse droplets can achieve control of grass weeds using contact herbicides with the correct herbicide rates and spray set-up.
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