Raptor at three rates and Pursuit at two rates were applied May 1995 to soybeans to evaluate tolerance of the rotational crops wheat, grain sorghum, and canola, planted Oct. 1995, May 1996, and Sept. 1996, respectively. There was no injury or stand reduction observed to the soybeans or the rotational crops winter wheat or grain sorghum. Similarly, differences in yield of soybean, winter wheat, and grain sorghum were not significant. As of Nov. 15, 1996, no injury has been observed to the canola planted Sept. 1996.

I. INTRODUCTION:

Raptor (AC 299,263) is an experimental, broad spectrum herbicide in the imidazilinone family. In contrast to Scepter or Pursuit, it has a shorter period of residual (half-life) and is more effective in controlling annual grasses than Pursuit when applied postemergence. This study was conducted to evaluate tolerance of Raptor applied postemergence over soybeans (in 1995) to the rotational crops, winter wheat, grain sorghum, and canola. Winter wheat was planted Oct. 12, 1995 following harvest of the soybeans. Grain sorghum was planted May 25, 1996 and Canola was planted Sept. 11, 1996 into plots treated with Raptor May 1995. 'Stripsū of canola also were planted Oct. 5, 1995 at the end of each 'tierū to evaluate canola tolerance to Raptor applied approximately five months earlier. All plots were kept essentially weed-free throughout the growing season with a combination of scheduled and other appropriate nonresidual herbicides, mechanical cultivation, and handweeding.

II. HERBICIDES EVALUATED:

        Raptor (AC 299,263) 1 AS
        Pursuit 1 AS

III. OTHER HERBICIDES USED:

        A.      On Soybeans: None in 1995; 1 qt Storm + 1 qt Poast + 1 qt crop oil                 concentrate in
                1996.
        B.      On Wheat: None
        C.      On Grain Sorghum: 1.25 pt/A Buctril in 1996 postemergence.
        D.      On Canola: None fall 1996.

IV. ABBREVIATIONS USED:

        BRSNS: Canola
        BROSOI: broadcast soil
        CSR: crop stand reduction
        GLXMA: soybeans
        SORVU: grain sorghum
        STR: strips
        TRZAW: winter wheat
        V31995: soybean 3d vegetative stage, 1995

 V. RESULTS AND DISCUSSION:

A. Soybeans, 1995: There was no soybean injury related to any of the herbicide applications in 1995 with a very uniform stand of soybeans in this study. Yield ranged from 42 to 46 bu/A with no significant difference between treatments.

B. Wheat 1995-1996: Wheat stand on April 16, 1996 was rated as 87 to 90% of a perfect stand. The less than perfect stand was related to poor emergence conditions fall 1996 and several freezing temperatures spring 1996 following renewed growth in the spring. Differences in stand between treatments was not significant. Percent stand was rated April 16 and reflects growth relative to that which might have occurred under ideal growing conditions. This stunt likely was related to the several freezes noted above. Similar stunt was observed in adjacent wheat areas where no herbicide had been applied. The stunt ranged from 22 to 30%, with no difference between treatments. Test weight ranged from 55.0 to 55.7 lb/bu, again with no difference related to herbicide treatments applied. Wheat yield ranged from 51 to 71 bu/A. Despite this wide range, differences were not significant at the 5% level of probability. Further, plots that had been treated with Raptor at 0.125 lbai/A (16 oz/A product) had among the highest yield in the study, 67 bu/A, compared to only 56 bu/A in the no herbicide plots.

C, Grain Sorghum, 1996: Grain sorghum was planted May 25, 1996 into a series of plots that had been treated with Raptor or Pursuit in May 1995. There was no indication of any injury or stand reduction to the sorghum in 1996 at any time during the season. Yield ranged from 133 to 141 bu/A, but these differences were not significant.

D. Canola, 1995: 'Strips' of canola were planted Oct. 5, 1995 across the end of all plots to evaluate tolerance four months after herbicide application. Because of low soil moisture at planting, a poor stand emerged. However, there appeared to be no difference in stand and no visual injury in these strips, regardless of prior herbicide application. The several freezes spring 1996

killed all of the canola, precluding evaluation of possible carryover injury.

E. Canola, 1996: ST994 brand canola was planted Sept. 11, 1996 to evaluate canola tolerance the year after application of Raptor and Pursuit. As of Nov. 15, 1996, an excellent stand had been established with no injury evident in any of the plots. On Nov. 15, a dense stand of canola was present that was about 15 inches tall. Yield will be obtained in 1997 unless winter-kill destroys the crop. 

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