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Effect of Application Rate, Weed Species, and Weed Stage of Growth on Imazethapyr Activity

Published online by Cambridge University Press:  12 June 2017

Tracy E. Klingaman ,
Charles A. King  and
Lawrence R. Oliver
Tracy E. Klingaman
Affiliation:
Dep. Agron., Univ. Arkansas, Fayetteville, AR 72701
Charles A. King
Affiliation:
Dep. Agron., Univ. Arkansas, Fayetteville, AR 72701
Lawrence R. Oliver
Affiliation:
Dep. Agron., Univ. Arkansas, Fayetteville, AR 72701
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Abstract

Field experiments were conducted in 1986, 1987, and 1988 to evaluate imazethapyr rate and time of application on postemergence control of 24 weed species. Contour graphs were developed that predicted imazethapyr rates required for various levels of weed control based upon weed leaf number at application. Rates below the labeled rate (70 g ha−1) provided 90% or greater control of common cocklebur, smallflower morningglory, and smooth pigweed if applied to 3 true-leaf or smaller weeds and of barnyardgrass, seedling johnsongrass, and Palmer amaranth if applied while weeds were in the cotyledon or 1 true-leaf stage. A rate of 70 g ha−1 provided 90% control of large crabgrass in the 1 true-leaf stage. Entireleaf morningglory, red rice, pitted morningglory, and velvetleaf are not susceptible enough to imazethapyr for 90% or greater control to be obtained with rates lower than 70 g ha−1 at the 1 true-leaf growth stage. These data demonstrate how control data can be used for developing effective reduced-rate herbicide recommendations based on weed leaf number.

Keywords

Imazethapyr, (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-ethyl-pyridinecarboxylic acidbarnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCGcommon cocklebur, Xanthium strumarium L. # XANSTentireleaf morningglory, Ipomoea hederacea var. integriuscula Gray # IPOHGjohnsongrass, Sorghum halepense (L.) Pers. # SORHAlarge crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSAPalmer amaranth, Amaranthus palmeri S. Wats. # AMAPApitted morningglory, Ipomoea lacunosa L. # IPOLAred rice, Oryza sativa L. # ORYSAsmallflower morningglory, Jacquemontia tamnifolia (L.) Griseb. # IAQTAsmooth pigweed, Amaranthus hybridus L. # AMACHvelvetleaf, Abutilon theophrasti Medik. # ABUTHContour graphsreduced ratestime of applicationABUTHAESVIAMACHAMAPAAMATUANVCRCASOBCLYMUCRIHADATSTDIGSAECHCGIAQTAIPOHGIPOLAIPOWRORYSAPHBPUSEBEXSETFASIDSPSORHAELEINXANST
Type
Weed Control and Herbicide Technology
Information
Weed Science , Volume 40 , Issue 2 , June 1992 , pp. 227 - 232
Copyright
Copyright © 1992 by the Weed Science Society of America 

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References

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