Field bindweed is a major weed problem for wheat producers across the Great Plains and for Oklahoma hard red winter wheat producers. Herbicides have demonstrated limited efficacy, with retreatment often suggested on labels. However, little data are available to verify efficacy with repeated treatments in Oklahoma wheat fields. Annual treatment with dicamba 2,4-D, the prepackaged mixture (premix) glyphosate 2,4-D, premix quinclorac 2,4-D at two different rates, or picloram 2,4-D to actively growing field bindweed for three consecutive years reduced stem density up to 88% at Lahoma and up to 96% at Stillwater for several months after treatment. However, by 12 to 14 mo after the last treatment, stem densities returned to 47% or more of the nontreated. Treatments applied in June or July were not more effective than treatments applied in September. These results suggested a need to shift the intent of herbicide application from multiyear control to single-year control with treatments designed to control field bindweed throughout one growing season. To field test this approach, nine farmer cooperators in 1998 to 1999 and seven cooperators in 1999 to 2000 applied either premixed glyphosate 2,4-D or dicamba in late summer or early fall after the field bindweed was allowed to grow 5 wk or more without disturbance. Of the participants, 88% reported little field bindweed present at wheat harvest, whereas 12% reported considerable field bindweed present at harvest. Cooperators were generally satisfied with the reduction in field bindweed canopy through harvest.
Nomenclature: 2,4-D; dicamba; glyphosate; picloram; quinclorac; field bindweed, Convolvulus arvensis L. #3 CONAR; wheat, Triticum aestivum L.
Additional index words: 2,4-D, dicamba, glyphosate, weed management.
Abbreviations: DAH, days after wheat harvest; OM, organic matter; premix, prepackaged mixture.
