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ISSUE 9  June 29, 2000

 

NOZZLES: MINIMIZING DRIFT AND MAINTAINING
HERBICIDE PERFORMANCE

    Nozzles designed to reduce spray drift by producing larger spray droplets are currently available from several manufacturers. These include Drift Guard (pre-orifice), Turbo TeeJet (pre-orifice, flooding flat-fan), and AI TeeJet (venturi) nozzles from Spraying Systems Co.; the TurboDrop (venturi) nozzle from Greenleaf Technologies Inc.; the Lurmark Ultra-Lo-Drift (venturi) nozzle from Precision Fluid Control Products; and the Spraymaster Raindrop Ultra (venturi) nozzle from Delavan Spray Technologies.

    Pre-orifice nozzles, such as the Drift Guard, regulate the liquid flow rate prior to the exit orifice. This causes a pressure drop within the nozzle so fewer fine spray droplets are produced. The Turbo TeeJet combines the pre-orifice technology with a flooding design and produces a wide-angle flat-fan spray pattern that greatly reduces the amount of spray in fine droplets. Although there are several distinct designs of venturi nozzles, the technology is basically the same. Each includes a pre-orifice
to regulate the flow rate so a larger exit orifice can be used to produce the spray pattern. Additionally, venturi nozzles include an air-induction assembly that incorporate air into the liquid stream thereby forming air-filled spray droplets.

    Research at North Dakota State University has shown the greatest reduction in spray drift is with venturi type nozzles (70 psi) or Turbo TeeJet nozzles operated at low pressure (20 psi). Drift Guard nozzles significantly reduce drift compared to a standard flat-fan nozzle, but still produce a quantity of fine droplets that result in greater spray drift than venturi or Turbo TeeJet nozzles.

    Weed control of two translocated herbicides, Roundup Ultra (glyphosate) and Raptor (imazamox), and two contact herbicides, Gramoxone Extra (paraquat) and Aim (carfentrazone) was similar for all nozzle designs. The drift-reducing nozzles performed as well as a standard flat-fan nozzle even when applied at a spray volume of 5 gpa. Spray coverage detected by water-sensitive cards was less for drift-reducing nozzles compared to a standard nozzle, but was still adequate for similar
grass species control by paraquat, a fast-acting contact herbicide.

    Important to the performance of venturi nozzles is the operating pressure. Most venturi nozzles have a minimum spray pressure of 40 psi, but for applying postemergence herbicides, pressures above 60 psi are recommended to maximize herbicide performance. The air-induction system operates more efficiently at higher spray pressures and in contrast to standard flat-fan nozzles, the droplet size spectrum of venturi nozzles is not greatly influenced by this pressure change.

    For maximum drift control without affecting herbicide performance, use venturi type nozzles at 60 psi and above or Turbo TeeJet nozzles at low spray pressures. Be aware that contact herbicides, hard-to-wet weed species, and small target weeds are examples where herbicide performance may influenced by drift-reducing nozzles. Remember to always read the label as some herbicides place restrictions on the spray application equipment which can be used.

Dr. Brad Ramsdale
NDSU Weed Science, Application Technology
ramsdale@prairie.nodak.edu

 

NDSU WEEDS TOUR CANCELLED

    Our weeds group stigma is still holding true: If you want a deluge, just schedule a weeds field tour. Due to excessive rains which destroyed or severally injured many experiments at the Casselton Agronomy Seed Farm, NW-22, and airport locations the NDSU Weeds Tour scheduled for July 6th has been cancelled. We considered using boats and canoes instead of hay wagons but dropped that idea when Phil Glogoza, NDSU Entomologist, forecasted the next major mosquito (!#*% bloodsucking vermin) hatch. We may appease Mother Nature one of these years but not this time.

 

ND SLN LABEL FOR TOUGH HERBICIDE IN MINT

    The North Dakota Department of Agriculture issued a special local needs registration (SLN) Friday, enabling North Dakota peppermint and spearmint producers to use the herbicide Tough 5EC to control broadleaf weeds in their fields. The SLN was issued because no herbicides are presently registered for mint.

    Tough control some broadleaf weeds including pigweed, kochia cocklebur, nightshade, sunflower, Russian thistle and lambsquarters. The SLN allows up to two ground applications of Tough 5EC at a rate of 24 ounces per acre. Treated plants cannot be grazed or fed to livestock. A 49-day pre-harvest interval must be observed. Users must follow all directions, precautions and warnings on the Section 3 and SLN labels and have the SLN label in their possession during application. The user assumes ALL liability of performance and crop injury from use.

 

ND SECTION 18 FOR PLATEAU HERBICIDE FOR LEAFY SPURGE CONTROL

    The EPA has approved an North Dakota Section 18 exemption for the herbicide Plateau for use in pasture and rangeland for leafy spurge control.

    Tordon has been used as the herbicide of choice for leafy spurge control but is restricted from use in area with highly permeable soils where Tordon could leach into groundwater. The Section 18 emergency registration allows Plateau to be used in pasture and rangeland, including CRP to control leafy spurge infestations.

    The exemption allows a single application of PlateauŽ at a rate of 12 fluid ounces of product per acre. Hay may not be harvested from treated acres for at least seven days. A maximum of 95,000 acres may be treated, and the exemption expires Dec. 31. Applicators must follow all directions, warnings and precautions on the label.

 

HERBICIDES APPLIED TO STRESSED SOYBEAN AND DRY BEANS

    Weeds will metabolize herbicides when actively growing. Cold temperatures and extreme water logged soil conditions can adversely affect weed control and soybean and dry bean response to herbicides. Plants essentially shut down during prolonged periods of standing water. Iron chlorosis and root rot may significantly impact bean growth. Weed and crop metabolism can be reduced to very low levels. Weed control may be impacted and crop injury increased under these conditions.

    American Cyanamid advises users of Pursuit and Raptor herbicides of the following recommendations for North Dakota and Minnesota growers:

    For optimal weed control and crop safety under the adverse environmental conditions, apply bean herbicides in the following manner:

    1. Allow standing water to drain from fields
        before making herbicide applications.

    2. Allow stressed plants to resume normal growth
        and color before applying herbicides. Apply herbicides
        prior to crop bloom.

    3. Tank-mix herbicides only when necessary and
        follow manufacturer adjuvant recommendations.

    Consult your local Cyanamid representative for more specific information. Always read
and follow label directions carefully.

 

IMPORT PROCESS HALTED FOR ACHIEVE 80DG

    The EPA has ceased signing import forms for the herbicide Achieve* 80DG, thereby preventing North Dakota producers and chemical dealers from importing the product from Canada. The decision came after Zeneca chemical company filed a formal complaint with the federal agency.

    Many North Dakota producers and dealers have purchased Achieve 80DG in Canada and brought it back to the country and saved between $5.90 and $6.25 per acre compared to the Achieve 40DG, which is currently sold in the U.S.

    EPA has indicated that they "do not approve or disapprove" of the action North Dakota has taken. However, EPA will not sign off on the required import form until a decision has been reached.

    The import form - "EPA Form 3540-1" (Notice of Arrival of Pesticides and Devices) - together with the Achieve 80DG label and a list of procedures can be found and copied from the North Dakota Department of Agriculture website at

www.agdepartment.com

    The EPA has not made a final determination on whether North Dakotans can import the herbicide from Canada.

 Richard Zollinger
NDSU Extension Weed Specialist
rzolling@ndsuext.nodak.edu


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