| dc.description.abstract | Field experiments were conducted to determine the tolerance of navy and pinto
bean, dry pea, and lentil to pyroxasulfone. Additional field studies were conducted to
evaluate the weed control efficacy of pyroxasulfone in preemergence and early-preplant
applications. Greenhouse experiments were conducted to determine plant uptake of
pyroxasulfone and the influence of activation timing on navy bean injury. Navy bean
tolerance to pyroxasulfone varied by rate and experiment location. Navy bean injury
occurred at 166 g ai ha-1 in 2008 and at 332 g ai ha·1 in 2009. A pyroxasulfone rate of 166
g ai ha·1 and greater resulted in decreased yield of navy bean. Pinto bean injury from
pyroxasulfone varied by location. As pyroxasulfone rate increased, visual injury to pinto
bean increased at Prosper in 2008; however, no pinto bean injury was observed at Prosper
in 2009. Pinto bean injury was observed in all other environments at 332 g ai ha· 1
• Pinto
bean yield was not reduced. Dry pea tolerance was excellent in all environments tested;
however, the lack of weed control in all environments was evidence that pyroxasulfone
was not activated by precipitation received. Lentil tolerance was excellent in all
environments tested, except for Minot 2009. Visual injury at Minot 2009 increased from
14 to 28 d after emergence, and then decreased to insignificant levels 56 d after emergence.
Lentil yield was not affected at any environment; however, a lack of weed control in all
environments, except for Minot 2009, was caused by inadequate precipitation to activate
the herbicide. These studies suggest that navy bean may not have sufficient tolerance to pyroxasulfone for field use. More research should be performed on dry pea and lentil
tolerance to determine the extent of tolerance in various environments.
Weed control experiments showed both the potential and inconsistency of
pyroxasulfone. High weed control ratings in the 2008 EPP (early preplant) study, from 14
to 35 d after application, demonstrated the ability of pyroxasulfone to control weeds
growing prior to herbicide activation. Yellow foxtail (Setaria glauca (L.)) and hairy
nightshade (Solanum sarrachoides Sendt.) were controlled at 166 g ai ha· 1
• Wild mustard
(Brassica Kaber (DC.)), hairy nightshade, and redroot pigweed (Amaranthus retroflexus)
were controlled 70 dafter application at 166 g ai ha·1
• Redroot pigweed control at 125 g ai
ha·1 was equivalent to acetochlor in the PRE (preemergence) 2008 study. Yellow foxtail
control at an increased rate of 209 g ai ha·1 pyroxasulfone was equivalent to the yellow
foxtail control of acetochlor in the PRE 2008 study. Pyroxasulfone consistently controlled
all weeds better than S-metolachlor, except for yellow foxtail at a reduced rate.
Pyroxasulfone at the suggested use rate of 166 g ai ha·1 controlled all weeds tested, except
for marshelder, at the same level as acetochlor in the PRE studies. Rates of pyroxasulfone
higher than 166 g ai ha·1 were needed to control weeds at the same level as acetochlor, as
the growing season progressed.
Visual injury to navy bean with pyroxasulfone was found to be severe when
moisture activated the herbicide at the ground-crack stage in greenhouse experiments. No
injury occurred from herbicide activation at other timings. Soil with decreased organic
matter showed less injury. The soil placement study confirmed that pyroxasulfone can be
taken into a plant through both the roots and shoots; however, pyroxasulfone activity is
greatest through root uptake. | en_US |
