Weed Control and Sunflower Tolerance of DPX-R6447 and Sulfentrazone
P. Hendrickson

The study was conducted on a Heimdal silt loam soil with a 6.7 pH and 2.9% organic matter.  Sunflower (SF290 NL) was seeded on May 26^th, into 30 inch rows at 24,500 seeds/A.  Preplant incorporated (PPI) and preemergence (PRE) treatments were applied to 10-by 25-ft plots with a hand-boom plot sprayer calibrated to deliver 20 gpa at 20 psi through XR8003 flat fan nozzles (Table 1).    The POST treatments were applied with XR8002 flat fan nozzles calibrated to deliver 20 gpa at 35 psi.  The PPI treatments were incorporated twice with a cultiharrow.  The experimental design was a randomized complete block with three replicates. 

Weeds evaluated were yellow foxtail, common lambsquarters and redroot pigweed.  The trial area was heavily infested with yellow foxtail early in the season.  On June 20, both DPX-R6447 and sulfentrazone applied PPI and PRE provided >75% control of yellow foxtail (Table 2).  By July 20, DPX-R6447 applied PRE at 0.125 lb ai/A was the only treatment with > 75% yellow foxtail control.  Both treatments that included quizalofop-P-ethyl provided 99% control of the yellow foxtail.  The addition of pendimethalin to DPX-R6447 and sulfentrazone did not improve yellow foxtail control.  Both DPX-R6447 and sulfentrazone applied PPI and PRE provided excellent control of common lambsquarters and redroot pigweed. 

No differences in sunflower injury were detected (data not shown).  Due to the heavy yellow foxtail infestation, yields tended to increase as the yellow foxtail control increased (Table 2).