Outlook Alone and in Mixtures for Efficacy in Corn Outlook Alone and in Mixtures for Efficacy in Corn

The objective of the study was to compare Outlook (dimethenamid) alone and in various tank mixtures for season-long weed control in corn. Kochia control with most herbicides was 95% or more late in the season. However, Russian thistle control did not exceed 83% with any herbicide tested. Palmer amaranth control at 59 days after the postemergence treatments was similar among all herbicides, while green foxtail control was 93% or more with each treatment. All herbicides increased grain yields relative to the untreated control, but corn treated with Outlook or Verdict alone yielded less grain than the best yielding plots.


Introduction
Preemergence (PRE) weed control is an important component in any cropping system.Allowing corn to become established prior to competition from weeds is no exception.Several dozen different herbicides are currently labeled for PRE use in Kansas corn, and these herbicides vary in their efficacy and length of residual activity.The objective of this study was to compare several PRE herbicides alone and in combinations for efficacy in corn.

Materials and Methods
An experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, KS, to evaluate Outlook (dimethenamid) alone or with various mixtures for efficacy in corn.Herbicides (Table 2) were applied using a tractor-mounted, compressed CO 2 sprayer delivering 19.4 gpa at 30 psi and 4.1 mph.Application, environmental, and weed information is shown in Table 1.Plots were 10 by 35 feet and arranged in a randomized complete block design with four replications.Soil was a Beeler silt loam with 2.4% organic matter and pH of 7.6.Visual estimates of weed control were taken on June 17 and August 10, 2020.These dates were 5 and 59 days after the postemergence treatment (DAB), respectively.Corn yields were determined on October 6, 2020, by mechanically harvesting the center two rows of each plot and adjusting grain weights to 15.5% moisture.

Results and Discussion
Common sunflower control was 83 to 95% at 5 DAB and 80 to 93% control at 59 DAB, and did not differ between herbicide treatments (data not shown).All herbicides controlled kochia more than 90% at 5 DAB except Verdict (dimethenamid/ saflufenacil) applied PRE followed by Zidua SC (pyroxasulfone) postemergence (POST) (Table 2).Verdict alone, or with a drift control agent (DCA) PRE, and Verdict followed by Zidua SC controlled kochia less than 90% at 59 DAT.Zidua SC with Sharpen (saflufenacil) and Callisto (mesotrione) or Verdict PRE controlled Russian thistle the best at each rating date.However, no herbicide provided more than 81% Russian thistle control.Outlook alone, or with a DCA PRE, and Verdict plus Callisto PRE controlled Palmer amaranth 100% at 5 DAB; however, no difference occurred among herbicides for Palmer amaranth control at 59 DAB.Similarly, green foxtail control did not differ among herbicides at 5 DAT, and only Verdict alone PRE provided less than 95% foxtail control later in the season.Grain yields were 68 to 108 bu/a higher from herbicide-treated plots than from untreated plots (37.5 bu/a).However, yields were generally lowest when Outlook alone or Verdict alone were applied (105 to 108 bu/a).

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Figure 3 .
Figure 3. Verdict at 10 oz/a applied preemergence.Photo taken 56 days after the preemergence treatment.

Figure 4 .
Figure 4. Zidua SC at 3.3 oz/a plus Callisto 4.0 oz/a applied preemergence.Photo taken 56 days after the preemergence treatment.

Figure 5 .
Figure 5. Verdict at 10 oz/a plus Zidua SC at 3.3 oz/a applied preemergence.Photo taken 56 days after the preemergence treatment.

Table 2 .
Weed control and grain yield from the Outlook in corn trial