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Bruce Burdick
1109 S. Birch St.
Albany, MO 64402
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Email: BurdickB@missouri.edu

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Objective: The objective of this study was to determine if the addition of Dual II Magnum to Raptor plus Cobra treatments would provide enhanced residual control of problem weeds.

Methods: Soybeans were planted on May 28 into a conventionally tilled field. The beans were planted in wide rows to encourage late emergence of weeds.

Treatments were early post applied on June 19 to V1-V2 stage soybeans. Weeds ranged from cotyledon to 4" cocklebur, 1/4-1" giant foxtail and just emerging to 1" common waterhemp.

Raptor 1EC was applied at the rate of 5 ounces of product/acre. The Cobra 2EC rate was 4 ounce/acre and the Dual II Magnum (7.64EC) rates were 0, 10.7 and 21.4 ounces of product per acre, depending upon the treatment. All treatments were applied with a non-ionic surfactant (0.25% v/v) and 28% nitrogen solution (1.25% v/v) in a 20 gallon/acre water solution.

Results: Ratings were made July 29 and the efficacy results of the three treatments can be seen in the table below. Initial weed control following treatment was very good. Each of the treatments provided 100% control of giant foxtail, cocklebur and common waterhemp. The ratings in the table indicate that the addition of Dual II Magnum to the tank mix provided no enhanced giant foxtail control. The data do suggest that the Dual II Magnum provided an enhanced level of residual control of common waterhemp following the initial early post application. The level of cocklebur control following the treatments would have to be classified as disappointing for all treatments.

There was no adverse crop response from the addition of Dual II Magnum to the tank mix.

Treatment                                       Percent weed control
                                       Giant Foxtail  Cocklebur  Waterhemp

Raptor + Cobra without Dual II Mag          99            68         78

Raptor + Cobra + Dual II Mag 
(low rate)                                  99            77         90

Raptor + Cobra + Dual II Mag
(high rate)                                 98            60         98

      LSD 0.05                               6            12         12

Table 11: Study 3513