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 26th, 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. 

Table 1.  Application data
Date:     May 25, 2000 May 30, 2000 July/7/2000
Treatments applied:   PPI PRE Post
Temperature (F): Air: 35 Soil: 56 Air: 54 Soil: 54 Air: 70 Soil: 68
   % relative humidity 84 78 98  (light mist)
   % cloud cover 0 20 100
   Wind speed and direction calm 8 mph  North 3-9 mph  east
   Dew present? yes yes yes
   Time of day 5:30 AM 8:30 to 9:00 AM 8:30 AM

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). 

Table 2.  Weed control in Sunflower          
  6/20/00

-----------  7/20/00  ---------

Sunflower4
Treatment Rate   SETLU1 SETLU CHEAL2 AMARE3 yield
lb ia/A Timing

-------------  % control  ------------

lbs/ac
sulfentrazone 0.1875 PPI 75 40 100 100 1228
sulfentrazone 0.375 PPI 93 53 100 100 1562
sulfentrazone / quizalofop-P-ethyl 0.1875 / 0.055 PPI / POST 87 99 100 100 1650
DPX-R6447 0.125 PPI 89 50 100 100 1596
sulfentrazone 0.1875 PRE 87 27 95 93 943
sulfentrazone 0.375 PRE 94 67 100 100 1530
DPX-R6447 0.0625 PRE 78 33 90 90 1149
DPX-R6447 0.0938 PRE 97 60 98 99 1620
DPX-R6447 0.125 PRE 99 75 100 99 1637
DPX=R6447 / quizalofop-P-ethyl 0.125 / 0.055 PRE / POST 98 99 99 98 1885
DPX-R6447 + pendamethalin 0.0625 + 1 PRE 83 40 99 97 1409
sulfentrazone + pendamethalin 0.1875 + 1 PRE 83 33 100 99 1060
pendamethalin 1 PRE 27 20 83 80 877
check 0 check 0 0 0 0 497
LSD (0.05)     12 17 8 4 386
1SETLU = yellow foxtail (Setaria glauca)
2CHEAL = common lambsquarters Chenopodium album)
3AMARE = redroot pigweed (Amaranthus retroflexus)
4Harvest October 12, 2000
 
NDSU Vice President,
Dean and Director for Agricultural Affairs
NDSU Extension Service ND Agricultural
Experiment Station
NDSU College of Agriculture NDSU College of Human Development and Education