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ISSUE 1   May 6, 1999


    The herbicides that can be used in the micro-rate system and the suggested rates of each follow:

Betanex at 0.5 pt/A or 0.08 lb/A
Betamix at 0.5 pt/A or 0.08 lb/A
UpBeet at 1/8 oz/A or 0.004 lb/A
Stinger at 1.3 fl oz/A or 0.03 lb/A
Select at 2 fl oz/A or 0.03 lb/A
Assure II at 4 fl oz/A or 0.028 lb/A
Poast at 5.3 fl oz/A or 0.062 lb/A

    The micro-rate must include Betanex or Betamix plus UpBeet plus a methylated seed oil
adjuvant at 1.5% v/v. A minimum of 1 pt/A of methylated seed oil is needed and no more than
2 pt/A is needed regardless of spray volume. Choose Betanex when redroot pigweed is of
primary concern and use Betamix for other situations. Betamix Progress is not registered as a
micro-rate component. Stinger should be added to the micro-rate for improved control of weeds
such as common lambsquarters, wild buckwheat, cocklebur, sunflower, ragweed and nightshade.
One of the grass herbicides can be added for improved grass control. The micro-rate without a
grass herbicide will give 70 to 85% grass control so the grass herbicide could be applied alone
at a full rate later in the growing season rather than in combination. The micro-rate should be
applied a minimum of three times at a five to seven day interval. The first treatment should be
when the largest sugarbeet plants in the field are just past the cotyledon stage when the first two
true leaves are just visible. This generally occurs between 14 and 21 days after planting.

    Accurate herbicide application is easier with a broadcast sprayer as compared to a band sprayer.
The amount of herbicide being applied in the micro-rate is so low that accurate application is
essential. However, sugarbeet growers who band applied the micro-rate in 1998 generally
reported a high level of satisfaction on the survey. So, band spraying can provide good results
but the band should be 11 inches wide and band spraying should only be done when the
environment is favorable. Moderate to high winds can greatly reduce the weed control from
band applications since droplets that move out of the target band area provide no value. With
broadcast application, limited sideways displacement does not harm weed control because the
coverage will still be complete.

    An 80 degree even-spray nozzle should be set about 6.5 inches high for an 11-inch band at
40 psi. A 40 degree even-spray nozzle should be set about 13 inches high for an 11-inch band
at 40 psi. Spray droplet drift with the 80 degree nozzle would be less than with the 40 degree
nozzle since the 80 degree nozzle is much closer to the ground.

    The micro-rate survey results are presented on pages 64-70 in the 1998 Sugarbeet Research
and Extension Reports. Very few relationships were noted between application method and the
satisfaction rating in the survey. Spray pressure and spray volume had no noticeable effect on
satisfaction with the micro-rate.

    Nozzle plugging with the micro-rate was reported by 45% of the survey respondents. Measures
most likely to reduce nozzle plugging follow.

  1. Clean the sprayer frequently.
  2. Mix the herbicides in warm water or at least let the water warm to air temperature before
    adding herbicides rather than mixing immediately after the water comes form the well.
  3. Increase the pH of the spray solution by using ammonia or a basic blend adjuvant. Household
    ammonia with a 2% concentration of ammonia should be used at 1 gallon per 100 gallons
    of water. A basic blend adjuvant (Quad 7, Linkage, Newtone, Transactive) should be used
    at 1% v/v. The herbicides will lower the pH of the solution so the target pH after mixing
    should be pH 8 to 9. Ammonia should be added slowly as the tank is filled to avoid a high
    pH spike.
  4. Spray out the tank load immediately after mixing. Spray until the tank is empty and flush the
    sprayer with water before any spray residue can dry in the sprayer.
  5. Use one of the grass herbicides in the micro-rate. All of the grass herbicides reduced nozzle
    plugging in a one-nozzle small-volume test system but Assure II had more effect than Poast
    or Select.
  6. Use the minimum amount of agitation needed to keep the solution mixed.
  7. Pre-slurry the UpBeet in hot water or in water with pH 8 to 9.
  8. Recent work with the one-nozzle small-volume test system suggests that nozzle plugging is
    less with Betamix than Betanex.

    The micro-rate was used by 64% of the survey respondents in 1998 and 97% of the users
indicated that they intend to use the micro-rate again in 1999. As stated in mutual fund advertising,
"past success is no guarantee of future performance" but the results in 1998 with the micro-rate
were quite good and similar performance in 1999 is expected unless environmental conditions
in 1999 cause an unexpected detrimental effect on weed control. For example, a dry cool
environment may reduce weed control from the micro-rate as well as normal rate treatments.

Alan Dexter
NDSU/U of MN Extension Sugarbeet Weed Specialist

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