Volunteer Corn Control in Roundup Ready 2 Xtend® Soybeans


The objective of this study was to determine the influence of clethodim rate (Select Max® herbicide) and adjuvant type on volunteer corn control when tank mixed with Roundup PowerMAX® herbicide, XtendiMax® herbicide with VaporGrip® Technology, and Warrant® herbicide. 



  • This trial was performed in Nebraska, North Dakota, Illinois, and Iowa. 

  • In North Dakota and Iowa, corn seed was spread evenly over the trial area and shallowly cultivated prior to planting soybeans. In Nebraska, corn seed was spread evenly over the trial area prior to planting soybeans. In Illinois, soybeans were planted, then corn seed was planted in between soybean rows at a seeding rate of 10,000 seeds/acre.  

  • Plots were 4 rows wide, 30 feet long, and treatments were replicated 3 times.  

  • Herbicide treatments (Table 1) were applied with a backpack sprayer using Turbo TeeJet® Induction nozzles when volunteer corn plants were approximately 12 inches in height. 

  • The adjuvants used in this trial were MSO Ultra™ (MSO), Superb® HC (HSCOC), and Destiny® HC (HSMSOC).  

  • Plots were visually evaluated 7 days after treatment for soybean crop injury and 21 days after treatment for volunteer corn control.  

  • There was not a significant effect of location on volunteer corn control, so data were combined across all locations for analysis. 


  • For treatments including Select Max® herbicide without an adjuvant, volunteer corn control was significantly reduced when Select Max herbicide was tank mixed with Roundup PowerMAX® herbicide + XtendiMax® herbicide with VaporGrip® Technology + Warrant® herbicide with DRA (Treatment 2 and Treatment 10) compared to Select Max herbicide + Roundup PowerMAX herbicide (Treatment 1 and Treatment 9).

  • At the 6 fl oz rate of Select Max, the addition of HSMSOC to Roundup PowerMAX herbicide + XtendiMax with VaporGrip Technology + Warrant herbicide with DRA (Treatment 8) increased volunteer corn control to statistically similar levels to that of Treatment 1. 

  • Increasing the rate of Select Max herbicide to 9 fl oz and including either MSO (Treatment 12) or HSMSOC (Treatment 16) with Roundup PowerMAX herbicide + XtendiMax with VaporGrip Technology + Warrant herbicide with DRA increased volunteer corn control to levels statistically similar to those of Treatment 1 and Treatment 9. 

  • Volunteer corn control with Fusilade® herbicide (Treatment 17) was similar to treatments with Select Max herbicide that did not contain XtendiMax with VaporGrip Technology + Warrant herbicide (Treatment 1 and Treatment 9).  

  • Averaged across all treatments, the addition of MSO or HSMSOC resulted in increased volunteer corn control compared to HSCOC or no adjuvant (Figure 2).

  • When Roundup PowerMAX herbicide + XtendiMax with VaporGrip Technology + Warrant herbicide with DRA were in the tank, soybean injury was significantly greater compared to Roundup PowerMAX herbicide + Select Max herbicide (Figure 3). 



  • For this trial, overall, increasing the rate of Select Max herbicide increased volunteer corn control.

  • The addition of MSO or HSMSOC to tank mixes of Select Max herbicide + Roundup PowerMAX herbicide + XtendiMax with VaporGrip Technology + Warrant herbicide with DRA increased volunteer corn control.

  • These results suggest that to help overcome reduced volunteer corn control when Select Max herbicide is tank mixed with Roundup PowerMAX herbicide + XtendiMax with VaporGrip Technology + Warrant herbicide with DRA, increase the rate of Select Max herbicide and use an MSO or HSMSOC adjuvant, or use Fusilade herbicide.

  • These results may not replicate a field scenario where ears are dropped.




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